Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Bio-filtration of helminth eggs and coliforms from municipal sewage for agricultural reuse in Peru
    Yaya Beas, R.E. - \ 2016
    Wageningen University. Promotor(en): Grietje Zeeman; Jules van Lier; Katarzyna Kujawa. - Wageningen : Wageningen University - ISBN 9789461734945 - 187
    waste water treatment - waste water treatment plants - anaerobic treatment - helminth ova - anaerobic conditions - filtration - public health - afvalwaterbehandeling - afvalwaterbehandelingsinstallaties - anaërobe behandeling - wormeneitjes - anaërobe omstandigheden - filtratie - volksgezondheid

    Where fresh water resources are scarce, treated wastewater becomes an attractive alternative for agricultural irrigation. However, the presence of large amounts of pathogens, even in treated wastewater, constraints its productive use, which is aggravated when sanitation and public health are poor. Among pathogenic indicators, helminth eggs are one of the most persistent microorganisms in treated effluents that may survive for several months in the irrigated fields. Application of upflow anaerobic sludge blanket (UASB) reactors could contribute to decrease the pathogenic content in wastewater due to physical and biological interactions with the anaerobic sludge bed, such as filtration and entrapment. In this thesis, the potential of the anaerobic sludge bed to particularly remove helminth eggs, was investigated in four phases. In the first phase, a temperature of 4° C was fixed in the UASB reactors in order to reduce the biological activity of the sludge. Hence, the anaerobic sludge filtration capacity at different upflow velocities was studied. This phase of the research was performed in two experiments. The first one using latex beads, simulating helminth eggs, and the second one using real helminth eggs, predominating in Peruvian wastewater. First experimental results show that increasing the upflow velocity led to a decrease in the removal efficiency of latex beads. At the lowest upflow velocity of 0.3 m·h−1, 100% removal of latex beads was reached. At an upflow velocity higher than 1 m·h−1, the removal efficiency dropped under 90 %. The degree of stabilisation of the sludge nor the sludge bed volume did not have a significant effect. Second experiment's results show that with upflow velocities below 1.5 m·h−1 real helminth eggs removal is greater than 70 %. Simultaneously tested, total and faecal coliforms removal was less than 83 %. The most common helminth eggs species found in the studied wastewater were Ascaris lumbricoides, Trichuris spp. and Strongyloides spp. The second phase was performed using two lab-scale UASB reactors at average ambient temperatures between 16.7 °C and 28.5 °C in the city of Lima (Peru). Ascaris suum eggs originating from infected pigs were selected as model organisms, considering their similarity, in terms of size and morphology, with Ascaris lumbricoides, a human pathogen. The sludge filtration capacity was determined, applying upflow velocities between 0.09 and 0.68 m·h−1. Average helminth eggs removals varied between 26 and 93 %, depending on upflow velocity and sludge bed height. 93 % removal was achieved when applying an upflow velocity of 0.09 m·h−1 and a sludge bed height reaching 19-25 % of the total reactor height. The third phase was conducted to test the effect of lower operational temperatures in the UASB reactor on the pathogen removal from domestic wastewater. Thus, a lab scale UASB reactor in the city of Puno (Peru), treating wastewater with temperatures varying between 11.3 and 14.3 °C for a period of 22 weeks after the start-up of the reactor, was used. Upflow velocities varied between 0.12 and 0.41 m·h−1. Results confirmed outcomes of the first phase of this research concerning helminth eggs removal, and consequently show that the sludge bed filtration capacity varied between 89 and 95 %. Faecal coliform removal varied between 0.9 and 2.1 log10 and E. coli removal between 0.8 and 1.6 log10. In general, removal efficiencies regarding helminth eggs and faecal coliforms, are not sufficient to comply with reuse standards. Finally, the capacity of Down Flow Hanging Sponge (DHS) reactors for removing faecal coliforms from domestic UASB reactor effluent for agricultural reuse in developing countries was investigated. Applied reactors were the cube type DHS (G1) without recirculation, the cube type DHS (G1) with recirculation and the curtain type DHS (G2). Results reveal an average faecal coliform removal of 4.74, 3.42 and 1.25 log10 respectively. These results comply with categories A, B and C of WHO (1989) standards, correspondingly. Therefore, treatment trains consisting of UASB-DHS reactors can possibly be applied when agricultural reuse is contemplated.

    A Downflow Hanging Sponge (DHS) reactor for faecal coliform removal from an Upflow Anaerobic Sludge Bed (UASB) effluent
    Yaya Beas, R.E. ; Kujawa-Roeleveld, K. ; Lier, J.B. van; Zeeman, G. - \ 2015
    Water Science and Technology 72 (2015)11. - ISSN 0273-1223 - p. 2034 - 2044.
    faecal coliforms - biochemical oxygen demand - chemical oxygen demand - waste water - waste water treatment - anaerobic treatment - waste water treatment plants - fecale coliformen - biochemisch zuurstofverbruik - chemisch zuurstofverbruik - afvalwater - afvalwaterbehandeling - anaërobe behandeling - afvalwaterbehandelingsinstallaties
    This research was conducted to study the faecal coliforms removal capacity of Downflow Hanging Sponge (DHS) reactors as a post-treatment for an Upflow Anaerobic Sludge Blanket (UASB) reactor. Three long-term continuous lab-scale DHS reactors i.e. a reactor with cube type sponges without recirculation, a similar one with recirculation and a reactor with curtain type sponges. The porosities of the applied medium were 91%, 87% and 47% respectively. The organic loading rates were 0.86 kgCOD m-3 d-1, 0.53 kgCOD m-3 d-1 and 0.24 kgCOD m-3 d-1 correspondingly at hydraulic loading rates of 1.92 m3 m-2 d-1, 2.97 m3 m-2 d-1 and 1.32 m3 m-2 d-1, respectively. The corresponding averages for faecal coliform removal were 99.997%, 99.919% and 92.121% respectively. The WHO (1989) standards, in terms of faecal coliform content for unrestricted irrigation (Category A), was achieved with the effluent of the cube type DHS (G1) without recirculation. Restricted irrigation, category B and C is assigned to the effluent of the cube type with recirculation and the curtain type, respectively. Particularly for organic compounds, the effluent of evaluated DHS reactors complies with USEPA standards for irrigation of so called non-food crops like pasture for milking animals, fodder, fibre, and seed crops.
    Influence of phenylacetic acid pulses on anaerobic digestion performance and archaeal community structure in WWTP sewage sludge digesters
    Cabrol, L. ; Urra, J. ; Rosenkranz, F. ; Kroff, P.A. ; Plugge, C.M. ; Lesty, Y. ; Chamy, R. - \ 2015
    Water Science and Technology 71 (2015)12. - ISSN 0273-1223 - p. 1790 - 1799.
    rioolslib - anaërobe behandeling - anaërobe afbraak - sewage sludge - anaerobic treatment - anaerobic digestion - waste-water treatment - olive mill wastewaters - volatile fatty-acids - 16s ribosomal-rna - biogas production - degradation efficiency - microbial-populations - aromatic-compounds - phenolic-compounds - inhibition
    The effect of phenylacetic acid (PAA) pulses on anaerobic digestion (AD) performance and archaeal community structure was evaluated in anaerobic digesters treating sewage sludge from a wastewater treatment plant (WWTP). Four pilot-scale continuous stirred tank reactors were set up at a full-scale municipal WWTP in Santiago de Chile, and fed with either primary or mixed sewage sludge. AD performance was evaluated by volatile fatty acid (VFA) and biogas production monitoring. Archaeal community structure was characterized by 16S rRNA denaturing gradient gel electrophoresis and band sequencing. In the primary sludge digester, a single PAA pulse at 200 mg L(-1) was sufficient to affect AD performance and archaeal community structure, resulting in long-term VFA accumulation, reduced biogas production and community shift from dominant acetoclastic (Methanosaeta concilii) to hydrogenotrophic (Methanospirillum hungatei) methanogens. By contrast, AD performance and archaeal community structure in the mixed sludge digester were stable and resistant to repeated PAA pulses at 200 and 600 mg L(-1). This work demonstrated that the effect of PAA pulses on methanogenic activity and archaeal community structure differed according to AD substrate, and suggests that better insights of the correlations between archaeal population dynamics and functional performance could help to better face toxic shocks in AD
    Bodem Resetten: stap naar praktijktoepassing nieuwe methode van anaerobe grondontsmetting
    Runia, W.T. ; Molendijk, L.P.G. ; Visser, J.H.M. ; Regeer, H. ; Feil, H. ; Meints, H. - \ 2015
    Lelystad : PPO AGV (Rapport / PPO-AGV 648) - 45
    akkerbouw - nematoda - meloidogyne chitwoodi - ditylenchus dipsaci - globodera pallida - waardplanten - gewasbescherming - bodeminvertebraten - nederland - inventarisaties - anaërobe behandeling - biologische grondontsmetting - duurzaamheid (sustainability) - onkruiden - nutrientenbeheer - arable farming - nematoda - meloidogyne chitwoodi - ditylenchus dipsaci - globodera pallida - host plants - plant protection - soil invertebrates - netherlands - inventories - anaerobic treatment - biological soil sterilization - sustainability - weeds - nutrient management
    Door de toenemende problemen met schadelijke aaltjes in diverse teelten wordt naarstig gezocht naar alternatieve mogelijkheden om de grond te ontsmetten. Uitgangspunt van Wageningen UR en Agrifirm Plant is daarvoor een “groene” manier van grondbehandeling, die past in het algemene beleid van een duurzame gewasbescherming. Bodem Resetten is een nieuwe en unieke manier van anaerobe grondontsmetting en kan mogelijk een milieuvriendelijk en voor omwonenden veilig alternatief bieden. Er zijn voor het Bodem Resetten (BR) twee producten getest op effectiviteit: vaste Herbie® 72 en vloeibare Herbie® 87. Tevens is op zeer kleine schaal ook een plantaardige coating, als alternatief voor folie, onderzocht op gasdichtheid.
    Anaerobic degradation of anionic surfactants by denitrifying bacteria
    Paulo, A. - \ 2014
    Wageningen University. Promotor(en): Fons Stams, co-promotor(en): P.A. García-Encina; Caroline Plugge. - Wageningen : Wageningen University - ISBN 9789462571242 - 166
    oppervlaktespanningsverlagende stoffen - degradatie - anaërobe microbiologie - anaërobe behandeling - denitrificerende bacteriën - afvalwaterbehandeling - rioolwaterzuivering - pseudomonas syringae pv. pisi - surfactants - degradation - anaerobic microbiology - anaerobic treatment - denitrifying bacteria - waste water treatment - sewage treatment - pseudomonas syringae pv. pisi
    De verwijdering van organische stof alsook van stikstof en fosfor wordt in RWZI vaak bewerkstelligd middels een anaëroob-anoxisch-aëroob (A2/O) proces. Met behulp van het A2/O proces kunnen oppervlakte-actieve stoffen al in het anaërobe dan wel anoxische compartiment afgebroken worden. In dit proefschrift wordt de isolatie van Pseudomonas stutzeri stam SN1 en Pseudomonas nitroreducens stam SN2 uit actief slib van een RWZI met een A2/O proces beschreven.
    Phosphate and organic fertilizer recovery from black water
    Tervahauta, T.H. - \ 2014
    Wageningen University. Promotor(en): Cees Buisman; Grietje Zeeman, co-promotor(en): L. Hernandez Leal. - Wageningen : Wageningen University - ISBN 9789462570931 - 156
    afvalwater - fosfaten - afvalwaterbehandeling - organische meststoffen - terugwinning - anaërobe behandeling - zware metalen - hergebruik van water - waste water - phosphates - waste water treatment - organic fertilizers - recovery - anaerobic treatment - heavy metals - water reuse
    In this thesis the integration of treatment systems for black and grey water was investigated to improve resource recovery within source-separated sanitation concepts. Special focus was set on phosphate and organic fertilizer recovery from vacuum collected black water. Currently, the soil application of black water sludge is prohibited in the Netherlands due to elevated heavy metal concentrations.
    Calcium phosphate granulation in anaerobic treatment of black water: a new approach to phosphorus recovery
    Tervahauta, T.H. ; Weijden, R.D. van der; Flemming, R.L. ; Hernández, L. ; Zeeman, G. ; Buisman, C.J.N. - \ 2014
    Water Research 48 (2014)1. - ISSN 0043-1354 - p. 632 - 642.
    afvalwaterbehandeling - afvalhergebruik - slibzuivering - calciumfosfaten - fosfor - terugwinning - spectroscopie - infraroodspectroscopie - anaërobe behandeling - biobased economy - waste water treatment - waste utilization - sludge treatment - calcium phosphates - phosphorus - recovery - spectroscopy - infrared spectroscopy - anaerobic treatment - biobased economy - waste-water - precipitation - hydroxyapatite - struvite
    Recovery of phosphorus from wastewater as calcium phosphate could diminish the need for mining of scarce phosphate rock resources. This study introduces a novel approach to phosphorus recovery by precipitation of calcium phosphate granules in anaerobic treatment of black water. The granules formed in the Upflow Anaerobic Sludge Blanket (UASB) reactor at lab- and demonstration-scale were analyzed for chemical composition and mineralogy by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES), Electron microprobe (EMP), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and micro X-ray Diffraction (XRD). The granules had a diameter of 1–2 mm, organic content of 33 wt%, and phosphorus content of 11–13 wt%. Three calcium phosphate phases were identified in the granules: hydroxyapatite, calcium phosphate hydrate and carbonated hydroxyapatite. Without any addition of chemicals, 7 gP/person/year can be recovered with the calcium phosphate granules, representing 2% of the incoming phosphorus in the UASB reactor. As the heavy metal content was lower compared to other phosphorus recovery products, phosphate rock and phosphorus fertilizer, the calcium phosphate granules could be considered as a new phosphorus product.
    Anaerobic wastewater treatment of high salinity wastewaters: impact on bioactivity and biomass retention
    Ismail, S. - \ 2013
    Wageningen University. Promotor(en): Jules van Lier, co-promotor(en): Hardy Temmink; Caroline Plugge. - Wageningen : Wageningen UR - ISBN 9789461738189 - 144
    afvalwaterbehandeling - waterzuivering - afvalwater - anaërobe behandeling - zoutgehalte - biomassa - waste water treatment - water treatment - waste water - anaerobic treatment - salinity - biomass

    Anaerobic sludge bed reactor systems like the upflow anaerobic sludge blanket (UASB) and expended granular sludge bed (EGSB) reactors are currently the mostly applied high-rate reactor systems for anaerobic wastewater treatment. The success of both systems has changed the world conception of wastewater treatment with energy recovery being an intrinsic part of the treatment process, avoidance of excess sludge problems and extremely low space requirement. Nevertheless, while broadening the UASB reactor application to a diverse type of wastewaters, high salinity wastewaters were found to give an adverse effect to the granulation processes. Accumulation of Na+at high concentrations produced weaker and fluffy granules endangering the applicability of the mentioned sludge bed systems. In this thesis, research was conducted to investigate the mechanisms of destabilization of the granules at high Na+concentrations, while trying to improve the granules’ properties. Chapter 1gives an overview of high salinity wastewaters, the application and the bottlenecks of anaerobic wastewater treatment (AnWT) technology under extreme conditions. Focus is given to the granulation process as a key factor in the operation of high rate anaerobic reactors. Indeed, it is a complex process that involves physicochemical as well as biological mechanisms. A short overview of the previous research on anaerobic wastewater treatment processes for high salinity wastewaters is discussed, followed by granulation theories and processes. Referring to the imbalance in the monovalent to divalent cation ratio, the Ca2+augmentation approach is discussed in this chapter as a tool to establish a favourable ratio for the required granulation process. The chapter also discusses the need for extracellular polymeric substances (EPS) production, depending on the types of substrates, as a major factor for a successful granulation process. Specifically for high Na+concentrations, also the importance of K+and more specifically the K+/Na+ratio is discussed as a control regulator to alleviate the negative effects of Na+. Finally, the review discusses microbiological aspects related to the anaerobic treatment of high salinity wastewaters such as the adaptation of sludge to high Na+concentrations and the presence of halophilic/halotolerent microorganisms and their application in anaerobic wastewater treatment.

    In Chapter 2, the effects of high Na+concentrations on methanogenic sludge bed reactor systems were investigated. In three different UASB reactors a rapid acclimation to 5 or 15 g Na+/L was observed, showing satisfactory results for a period of 100 days, when the reactors were fed with a mixture of acetate, gelatine and ethanol. Loading rates up to at least 18 kg COD/m3.d gave a good COD removal performance and the cultivated sludge showed high specific methanogenic activities (SMA) on acetate, propionate, butyrate and H2compared to the inoculated granules. Remarkably, only the reactor which was operated at a lower COD (5 instead of 50 g/L) exhibited severe washout, probably due to the much shorter HRT that was applied, i.e. 12 hours compared to 120 hours. Interestingly, the SMA of the biomass that washed out from this reactor showed considerably higher SMAs than the washed-out biomass from the other reactors. The performance of the granular sludge systems in this study shows the appropriateness of anaerobic inocula, pre-grown under saline conditions for the anaerobic treatment of high salinity wastewater.

    In Chapter 3the production of EPS in UASB reactor systems that were operated under high salinity conditions was investigated. Four different UASB reactors were operated at loading rates up to 22 kg COD/m3.d with different acetate:gelatine:starch ratios as the substrate. Reactors were fed with partially acidified and fully acidified substrates, i.e. PAS and FAS respectively, and Na+concentrations of either 10 or 20 g Na+/L. One of the reactors additionally received 1 g of Ca2+/L. All four reactors showed a good performance with COD removal efficiencies exceeding 90 %. Proteins were the dominant EPS and the PAS-fed granules gave much higher EPS concentrations than FAS-fed granules. However, the proteins concentration was found not dependent on the Na+ concentration in the feed. Interestingly, the granules from the reactors which were operated at a Na+/Ca2+ratio of 770 contained more polysaccharides than granules from reactors operated at a high Na+/Ca2+ratio of 1540. SEM images showed that that PAS-fed granule had a smoother granule surfaces than FAS-fed granule. PAS-fed granules also were considerably larger than FAS-fed granules. When the influent contained additional Ca2+, clear cracks or fissures could be observed on the surface of the granules. Na+ concentrations of 10 g/L seemed to increase the granule size, which may have been caused by swelling of the EPS matrix. Shear tests indicated that PAS-fed granules were stronger than the FAS fed granules and that Ca2+ addition had a positive effect on granule strength. The calcium content of these granules also was higher with 150 mg/g TSS compared to 60 mg/g TSS in the other reactors. Batch tests at high Na+concentrations confirmed calcium leaching from the granules. When granular sludge was exposed to 20 g Na+/L in batches, leaching of Ca2+from granules took place with a maximum obtained after 10 days. The calcium content of the granules decreased from approximately 85 to 52 mg/g TSS. Therefore, the highest Na+concentrations resulted in the weakest granules.

    Chapter 4describes the results of batch incubation studies in which anaerobic granular sludge was augmented with 0.3 g Ca2+/L at Na+concentrations of 20 g/L. Experiments followed the previously described results of Chapter 3 showing that high Na+concentrations caused Ca2+leaching from anaerobic granules. Extensive SEM-EDX and SEM-BSE measurements confirm leaching of calcium from the granules when these are exposed to higher Na+ concentrations. Moreover Ca2+additions seemed to indeed maintain the Ca2+content of granular sludge.

    Initial attachment of microorganism is very important for the development of granules and biofilms. Therefore, biofilm studies were conducted and explained in Chapter 5. Four different biofilm reactors with a non-woven carrier material were exposed to different Na+ concentrations (10 or 20 g/L) and inoculated with crushed granules. Acetate was used as the substrate. One of the reactors received 0.3 g Ca2+/L and another one 0.7 g K+/L. The reactors were operated as sequencing batches. The reactor fed with K+ gave the best performance. Lower salinity (10 compared to 20 g Na+/L) improved the performance and the reactor which received calcium gave the worst results. This finding contradicts with previous experiments in Chapter 3. However, the situation in the biofilm reactors is completely different because the biofilms had to form from scratch. FISH-CLSM images revealed no significant visible differences in microbial coverage (i.e. bacteria and archea) of the non-woven fabric, except for the calcium enriched reactor. After 40 days of operation, it was clearly observed that 20 g Na+/L does not prevent the initial microbial attachment under anaerobic conditions. From 16 sRNA DGGE measurements it was shown that the biofilms had a similar population and that this population did not change very much in time. The Archea were related to Methanosaeta harundinacae (acetoclastic), Methanolinea tarda and Methanobacterium subteraaneum (both hydrogenotrophic). Apparently these species can easily adapt to high salinity. However, the biofilms in the reactors did not show any of the known acetate-oxidizing bacteria that are expectedly needed for the production of H2from acetate as source for the growth of the found hydrogenotrophic Archea. Therefore, it is assumed that H2leakage by acetoclastic methanogen explain their presence in the reactor.

    Four identical UASB reactors treating concentrated wastewaters (10 – 30 g COD/L) were operated at 20 g Na+/L and in detail described in Chapter 6. PAS and FAS substrates were fed to different reactors to compare the effect of different organic substrates on granule activity, stability and growth. The effect of calcium augmentation on anaerobic granules’ properties was studied by feeding two of the reactors with additional calcium at a concentration of 0.3 g Ca2+/L. A beneficial effect of potassium was demonstrated in Chapter 5 and it therefore was added to all the reactors, at a concentration of 0.7 g K+/L. The treatment performance of the reactors was compared during a period of 120 days at increasing volumetric organic loading rates (OLRs). Physicochemical and microbiological properties of the anaerobic granules were determined and discussed. The results showed that high COD removal efficiencies are possible at 20 g Na+/L, up to an organic loading rate of at least 14 g COD/L.d. At a loading rate of 25 g COD/L.d the performance and stability of all reactors deteriorated. There were indications that calcium augmentation had a positive effect on biomass retention, but this could not be further quantified. The microbial assays gave similar results as in Chapter 5. Compared to the inoculum, bacterial diversity in FAS-fed granules did not change significantly but was changed considerably in PAS-fed granules. Complex organic PAS feed resulted in more complex bacterial populations that were not related to archea. The bacterial presence of a dominant phylotype, belonging to the family of Marinilabiliaceaeand specifically Alkaliflexus imshenetskiiwas evidenced. Members of Marinilabiliaceae are capable of degrading polymeric substances such as starch and gelatine. The dominant archeal species in the reactors was related to Methanosaeta harundinacea. Methanosaetahave been found to play a major role in granulation

    In Chapter 7the results of this research are discussed in a general context. Directions for further research are presented focussing on the increase in biomass activity and biomass retention in high salinity wastewaters by improving the adaptability of microbes and the anaerobic sludge granulation process.

    New sanitation : bridging cities and agriculture
    Zeeman, G. - \ 2012
    Wageningen : Wageningen University, Wageningen UR - ISBN 9789461733252 - 23
    nieuwe sanitatie - afvalwater - afvalwaterbehandeling - afval - kringlopen - volksgezondheid - anaërobe behandeling - terugwinning - new sanitation - waste water - waste water treatment - wastes - cycling - public health - anaerobic treatment - recovery
    This inaugural lecture revolves around recovering raw materials such as phosphate, nitrogen, organic substances, energy and water from domestic waste and wastewater. If separated at source using less water, these materials can be recovered more efficiently and used as fertilisers in agriculture, for example. This is an important move at a time when raw materials are becoming increasingly scarce.
    The effect of sludge recirculation rate on a UASB-digester treating domestic sewage at 15 °C
    Zhang, L. ; Hendrickx, T.L.G. ; Kampman, C. ; Zeeman, G. ; Temmink, B.G. ; Weiguang Li, ; Buisman, C.J.N. - \ 2012
    Water Science and Technology 66 (2012)12. - ISSN 0273-1223 - p. 2597 - 2603.
    afvalwaterbehandeling - afvalwater - rioolwater - huishoudens - anaërobe behandeling - anaërobe verteerders - slibvergisting - recirculatiesystemen - temperatuur - zuurstofbehoefte - biogas - concentratie - efficiëntie - waste water treatment - waste water - sewage - households - anaerobic treatment - anaerobic digesters - sludge digestion - recirculating systems - temperature - oxygen requirement - biogas - concentration - efficiency - waste-water treatment - anaerobic-digestion - low-temperature
    The anaerobic treatment of low strength domestic sewage at low temperature is an attractive and important topic at present. The upflow anaerobic sludge bed (UASB)-digester system is one of the anaerobic systems to challenge low temperature and concentrations. The effect of sludge recirculation rate on a UASB-digester system treating domestic sewage at 15 °C was studied in this research. A sludge recirculation rate of 0.9, 2.6 and 12.5% of the influent flow rate was investigated. The results showed that the total chemical oxygen demand (COD) removal efficiency rose with increasing sludge recirculation rate. A sludge recirculation rate of 0.9% of the influent flow rate led to organic solids accumulation in the UASB reactor. After the sludge recirculation rate increased from 0.9 to 2.6%, the stability of the UASB sludge was substantially improved from 0.37 to 0.15 g CH4-COD/g COD, and the bio­gas production in the digester went up from 2.9 to 7.4 L/d. The stability of the UASB sludge and bio­gas production in the digester were not significantly further improved by increasing sludge recirculation rate to 12.5% of the influent flow rate, but the biogas production in the UASB increased from 0.37 to 1.2 L/d. It is recommended to apply a maximum sludge recirculation rate of 2–2.5% of the influent flow rate in a UASB-digester system, as this still allows energy self-sufficiency of the system.
    Autotrophic nitrogen removal from low strength waste water at low temperature
    Hendrickx, T.L.G. ; Wang, Y. ; Kampman, C. ; Zeeman, G. ; Temmink, B.G. ; Buisman, C.J.N. - \ 2012
    Water Research 46 (2012)7. - ISSN 0043-1354 - p. 2187 - 2193.
    afvalwaterbehandeling - afvalwaterbehandelingsinstallaties - stikstof - verwijdering - denitrificatie - temperatuur - anaërobe behandeling - ammonium - oxidatie - energiebesparing - stedelijk afvalwater - waste water treatment - waste water treatment plants - nitrogen - removal - denitrification - temperature - anaerobic treatment - ammonium - oxidation - energy saving - municipal wastewater - anaerobic ammonium oxidation - treat sewage - reactor - system
    Direct anaerobic treatment of municipal waste waters allows for energy recovery in the form of biogas. A further decrease in the energy requirement for waste water treatment can be achieved by removing the ammonium in the anaerobic effluent with an autotrophic process, such as anammox. Until now, anammox has mainly been used for treating warm (>30 °C) and concentrated (>500 mg N/L) waste streams. Application in the water line of municipal waste water treatment poses the challenges of a lower nitrogen concentration (
    The effect of operational conditions on the hydrodynamic characteristics of the sludge bed in UASB reactors
    Leitao, R.C. ; Santaellla, S.T. ; Haandel, A.C. van; Zeeman, G. ; Lettinga, G. - \ 2011
    Water Science and Technology 64 (2011)9. - ISSN 0273-1223 - p. 1935 - 1941.
    afvalwaterbehandeling - geactiveerd slib - anaërobe behandeling - slibzuivering - hydrodynamische dispersie - zuiveringsinstallaties - expansie - retentie - volume - waste water treatment - activated sludge - anaerobic treatment - sludge treatment - hydrodynamic dispersion - purification plants - expansion - retention - volume - settling characteristics - expansion characteristics - granular sludge - volume index - velocity - sewage - settleability - design
    This work aims to evaluate the hydrodynamic properties of the sludge bed of Upflow Anaerobic Sludge Blanket (UASB) reactors based on its settleability and expansion characteristics. The methodologies used for the evaluation of the settleability of aerobic activated sludge, and for the expansibility of a sludge bed of Expanded Granular Sludge Bed reactors and Fluidised Bed Reactors were adapted and applied to the particular characteristics of the sludge of UASB reactors. An easy-to-build experimental set-up was developed to assess the parameters necessary for the equations of settleability and of expansibility. The results obtained from the sludges of seven differently operated reactors show that, for the treatment of low strength wastewater, settleability increased and expansibility decreased at decreased hydraulic retention time, from 6 to 1 h, and/or increased influent concentrations, from 136 to approximately 800 mg chemical oxygen demand/L. The results also show that it is useless to design an UASB reactor with a longer hydraulic retention time to cope with hydraulic shock loads, as a more expansible sludge will develop at such condition.
    Diversity and enrichment of nitrite-dependent anaerobic methane oxidizing bacteria from wastewater sludge
    Luesken, F. ; Alen, T. van; Biezen, J. van der; Frijters, C. ; Toonen, G. ; Kampman, C. ; Hendrickx, T.L.G. ; Zeeman, G. ; Temmink, B.G. ; Strous, M. ; Camp, H.J.M. op den; Jetten, M.S.M. - \ 2011
    Applied Microbiology and Biotechnology (2011). - ISSN 0175-7598
    afvalwaterbehandeling - waterzuivering - anaërobe behandeling - methaan - oxidatie - bacteriën - nieuwe stam - denitrificerende micro-organismen - waste water treatment - water treatment - anaerobic treatment - methane - oxidation - bacteria - new phylum - denitrifying microorganisms - activated-sludge - microorganisms - populations - technology - reactor
    Recently discovered microorganisms affiliated to the bacterial phylum NC10, named “Candidatus Methylomirabilis oxyfera”, perform nitrite-dependent anaerobic methane oxidation. These microorganisms could be important players in a novel way of anaerobic wastewater treatment where ammonium and residual dissolved methane might be removed at the expense of nitrate or nitrite. To find suitable inocula for reactor startup, ten selected wastewater treatment plants (WWTPs) located in The Netherlands were screened for the endogenous presence of M. oxyfera using molecular diagnostic methods. We could identify NC10 bacteria with 98% similarity to M. oxyfera in nine out of ten WWTPs tested. Sludge from one selected WWTP was used to start a new enrichment culture of NC10 bacteria. This enrichment was monitored using specific pmoA primers and M. oxyfera cells were visualized with fluorescence oligonucleotide probes. After 112 days, the enrichment consumed up to 0.4 mM NO2- per day. The results of this study show that appropriate sources of biomass, enrichment strategies, and diagnostic tools existed to start and monitor pilot scale tests for the implementation of nitrite-dependent methane oxidation in wastewater treatment at ambient temperature
    Autogenerative high pressure digestion: anaerobic digestion and biogas upgrading in a single step reactor system
    Lindeboom, R.E.F. ; Fermoso, F.G. ; Weijma, J. ; Zagt, K. ; Lier, J.B. van - \ 2011
    Water Science and Technology 64 (2011)3. - ISSN 0273-1223 - p. 647 - 653.
    biogas - gasproductie - biochemische omzettingen - methaan - anaërobe afbraak - drukbehandeling - kooldioxide - oplosbaarheid - anaërobe behandeling - afvalwaterbehandeling - biobased economy - biogas - gas production - biochemical pathways - methane - anaerobic digestion - pressure treatment - carbon dioxide - solubility - anaerobic treatment - waste water treatment - biobased economy
    Conventional anaerobic digestion is a widely applied technology to produce biogas from organic wastes and residues. The biogas calorific value depends on the CH4 content which generally ranges between 55 and 65%. Biogas upgrading to so-called ‘green gas’, with natural gas quality, generally proceeds with add-on technologies, applicable only for biogas flows >100 m3/h. In the concept of autogenerative high pressure digestion (AHPD), methanogenic biomass builds up pressure inside the reactor. Since CO2 has a higher solubility than CH4, it will proportion more to the liquid phase at higher pressures. Therefore, AHPD biogas is characterised by a high CH4 content, reaching equilibrium values between 90 and 95% at a pressure of 3–90 bar. In addition, also H2S and NH3 are theoretically more soluble in the bulk liquid than CO2. Moreover, the water content of the already compressed biogas is calculated to have a dew point
    Energy and phosphorus recovery from black water
    Graaff, M.S. de; Temmink, B.G. ; Zeeman, G. ; Buisman, C.J.N. - \ 2011
    Water Science and Technology 63 (2011)11. - ISSN 0273-1223 - p. 2759 - 2765.
    afvalwaterbehandeling - urine - huishoudens - nieuwe sanitatie - energieterugwinning - fosfor - anaërobe behandeling - waste water treatment - urine - households - new sanitation - energy recovery - phosphorus - anaerobic treatment - nitrogen removal - waste-water - struvite - systems - precipitation - tank
    Source-separated black water (BW) (toilet water) containing 38% of the organic material and 68% of the phosphorus in the total household waste (water) stream including kitchen waste, is a potential source for energy and phosphorus recovery. The energy recovered, in the form of electricity and heat, is more than sufficient for anaerobic treatment, nitrogen removal and phosphorus recovery. The phosphorus balance of an upflow anaerobic sludge blanket reactor treating concentrated BW showed a phosphorus conservation of 61% in the anaerobic effluent. Precipitation of phosphate as struvite from this stream resulted in a recovery of 0.22 kgP/p/y, representing 10% of the artificial phosphorus fertiliser production in the world. The remaining part of the phosphorus ended up in the anaerobic sludge, mainly due to precipitation (39%). Low dilution and a high pH favour the accumulation of phosphorus in the anaerobic sludge and this sludge could be used as a phosphorus-enriched organic fertiliser, provided that it is safe regarding heavy metals, pathogens and micro-pollutants.
    Denitrificatie met opgelost methaan uit anaerobe vergisting: nieuwe mogelijkheid voor afvalwaterbehandeling
    Hendrickx, T.L.G. ; Kampman, C. ; Luesken, F. ; Temmink, B.G. - \ 2010
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 14 (2010)15. - ISSN 0166-8439 - p. 34 - 36.
    afvalwaterbehandeling - huishoudens - energieterugwinning - biogas - anaërobe behandeling - ammonium - methaan - denitrificatie - waterzuivering - zuiveringsinstallaties - waste water treatment - households - energy recovery - biogas - anaerobic treatment - ammonium - methane - denitrification - water treatment - purification plants
    Huishoudelijk afvalwater bevat veel energie. Rioolwaterzuiveringsinstallaties hebben zodoende de potentie om energieproducerend te worden in plaats van energieconsumerend. Er zijn reeds initiatieven in gang gezet die zich richten op het terugwinnen van energie in de vorm van biogas door het vergisten van primair en secundair slib. Een meer directe route naar biogas is de anaerobe zuivering van het afvalwater. Het effluent van een anaerobe reactor bevat echter nog wel ammonium en opgelost methaan (een sterk broeikasgas). Beide kunnen omgezet worden met de recentelijk ontdekte DAMO-bacteriën: denitrificatie gekoppeld aan anaerobe methaanoxidatie. Dit biedt nieuwe mogelijkheden voor een energie-efficiënte afvalwaterbehandeling.
    Hydrolysis inhibition of complex biowaste
    Vasconcelos Fernandes, T. - \ 2010
    Wageningen University. Promotor(en): Jules van Lier, co-promotor(en): Grietje Zeeman. - [S.l.] : S.n. - ISBN 9789085856818 - 182
    agrarische afvalstoffen - dierlijke meststoffen - drijfmest - biomassa - hydrolyse - verwerking - anaërobe behandeling - anaërobe afbraak - afvalverwerking - biogas - biomassaconversie - agricultural wastes - animal manures - slurries - biomass - hydrolysis - processing - anaerobic treatment - anaerobic digestion - waste treatment - biogas - biomass conversion
    The increasing demand of renewable energy sources and reuse of wastes, challenges our society for better technological solutions for energy production. Co-digestion of agricultural biowaste, such as animal manure and plant residues, offers an interesting contribution to the renewable energy strategies. The biogas plants, where the complex substrates, such as agricultural biowaste, get converted into biogas, are then able to produce electricity and heat, which can be used in the farm and delivered to the main electricity grid. Moreover, due to its decentralised nature, the implementation of small-scale biogas plants can supply renewable energy to people without the need for large-scale infrastructural networks such as electricity grids, thereby solving part of the populations’ energy demands.
    The production of biogas from complex biowaste is rate-limited by the hydrolysis step of the anaerobic digestion process. However the hydrolysis step has been poorly described and not very well understood, resulting in non-optimized anaerobic digester volumes. Due to that, a review on the anaerobic hydrolysis step is in this thesis presented, together with ways to accelerate the hydrolysis, either by mitigating the revealed inhibiting compounds, by pre-treating difficultly hydrolysable substrates, or as is nowadays also applied, by adding hydrolytic enzymes to full scale biogas co-digestion plants.
    In this thesis two compounds were studied in terms of its inhibiting effect on hydrolysis: ammonia nitrogen and Humic Matter (HM). Ammonia nitrogen did not show an inhibiting effect on anaerobic hydrolysis. On the other hand Humic acids-like (HAL) and Fulvic acids-like (FAL) extracted from fesh cow manure and silage maize, and in this thesis extensively described in terms of its chemical characteristics, showed a strong inhibiting effect on the hydrolysis step.
    Plant matter is high in lignocellulosic biomass. Lignocellulosic biomass consists of lignin, which is resistant to anaerobic degradation, cellulose and hemicelluloses. Pre-treatment of plant material, is particularly important in order to increase biogas production during co-digestion of manure. Calcium hydroxide pre-treatment was shown, in this thesis, to improve the biodegradability of lignocellulosic biomass, especially for high lignin content substrates. Maleic acid generated the highest percentage of dissolved COD during pre-treatment, however its high market price makes it not so attractive as calcium hydroxyde.
    Enzyme addition has recently gained the attention of biogas plants’ operators in order to accelerate hydrolysis, however further research is needed.

    Long term partial nitritation of anaerobically treated black water and the emission of nitrous oxide
    Graaff, M.S. de; Zeeman, G. ; Temmink, B.G. ; Loosdrecht, M.C.M. ; Buisman, C.J.N. - \ 2010
    Water Research 44 (2010)7. - ISSN 0043-1354 - p. 2171 - 2178.
    rioolafvalwater - rioolwater - excreten - huishoudens - afvoerwater - nieuwe sanitatie - afvalwaterbehandeling - nitrificatie - ammonium - anaërobe behandeling - sewage effluent - sewage - excreta - households - effluents - new sanitation - waste water treatment - nitrification - ammonium - anaerobic treatment - anammox reactor - waste-water - start-up - removal - ammonia - sharon - supernatant - management - digestion
    Black water (toilet water) contains half the load of organic material and the major fraction of the nutrients nitrogen and phosphorus in a household and is 25 times more concentrated, when collected with a vacuum toilet, than the total wastewater stream from a Dutch household. This research focuses on the partial nitritation of anaerobically treated black water to produce an effluent suitable to feed to the anammox process. Successful partial nitritation was achieved at 34 °C and 25 °C and for a long period (almost 400 days in the second period at 25 °C) without strict process control a stable effluent at a ratio of 1.3 NO2-N/NH4-N was produced which is suitable to feed to the anammox process. Nitrite oxidizers were successfully outcompeted due to inhibition by free ammonia and nitrous acid and due to fluctuating conditions in SRT (1.0–17 days) and pH (from 6.3 to 7.7) in the reactor. Microbial analysis of the sludge confirmed the presence of mainly ammonium oxidizers. The emission of nitrous oxide (N2O) is of growing concern and it corresponded to 0.6–2.6% (average 1.9%) of the total nitrogen load
    Combined carbon and nitrogen removal in integrated anaerobic/anoxic sludge bed reactors for the treatment of domestic sewage
    Kassab, G. - \ 2009
    Wageningen University. Promotor(en): Jules van Lier, co-promotor(en): B. Klapwijk; M. Fayyad. - [S.l. : S.n. - ISBN 9789085853886 - 130
    rioolwater - rioolslib - bioreactoren - anaërobe behandeling - anaërobe afbraak - denitrificatie - afvalwaterbehandeling - stikstof - verwijdering - koolstof - sewage - sewage sludge - bioreactors - anaerobic treatment - anaerobic digestion - denitrification - waste water treatment - nitrogen - removal - carbon
    The main objective of this research is to assess the applicability and effectiveness of integrating anaerobic digestion and denitrification processes in a single sludge system. The integrated concept is of particular interest for the treatment of highstrength domestic wastewater and is accomplished by means of a sequential anaerobic-aerobic system. The anaerobic pre-treatment can consist of a single anaerobic stage or two anaerobic stages, conditioned mainly by the wastewater characteristics, the prevailing ambient temperatures and the scale of application
    Characterization and treatment of grey water : option for (re)use
    Abu-Ghunmi, L.N.A.H. - \ 2009
    Wageningen University. Promotor(en): Jules van Lier, co-promotor(en): Grietje Zeeman; M. Fayyad. - [S.l. : S.n. - ISBN 9789085853930 - 194
    afvalwaterbehandeling - hergebruik van water - fysicochemische eigenschappen - filtratie - aërobe behandeling - anaërobe behandeling - jordanië - waste water treatment - water reuse - physicochemical properties - filtration - aerobic treatment - anaerobic treatment - jordan
    Addressing the issues of water shortage and appropriate sanitation in Jordan, domestic grey water treatment receives growing interest. Grey water comprises the domestic wastewater flows excluding waters associated with the toilet. The topics of concern for grey water are its characteristics, treatment and potentials for use after treatment. The target of this thesis is to develop a concept for treating grey water on-site for agricultural usage, thus sustaining a recycling process of grey water in Jordan. A review was made regarding the currently available grey water treatment technologies. In addition, grey water was quantitatively and qualitatively characterized, and then grey water reuse requirements including treatment, were analyzed. Biodegradability and biodegradation rates of the grey water were investigated for selecting appropriate design and operation criteria of the treatment technology to be developed. A low-tech semi-technical scale treatment system was tested to treat grey water discharges from a dormitory at the Jordan University campus. The treatment system was evaluated on obtained removal efficiencies and conformity of the effluent to the guidelines for the use of reclaimed water for irrigation in Jordan. Finally, the objectives, approaches and the results of each chapter are summarized, and then both the results and the potential of applying decentralised sanitation and reuse (DeSaR) concepts in Jordan are discussed.

    Results show that storage and treatment are prerequisites for any type of grey water use. Grey water is aerobically and anaerobically biodegradable but the conversion rates are low. The core of the treatment concept consists of an integrated storage and anaerobic treatment unit, fed with a natural influent flow pattern, in a down-flow mode, up to a one day operational cycle, i.e. a variable HRT ≤ 24 hours. The second step consists of an aerobic post-treatment, mechanically aerated in a down-flow mode and a one day operational cycle, i.e. 24 hours HRT. Both units need insulation in the winter period. The final effluent, stable in winter and summer, meets the Jordanian standard, except for the pathogens, for usage in restricted irrigation. The achievable treatment efficiency for the CODtot is 44% in the anaerobic unit and 70% in the combined anaerobic-aerobic, unlike the high anaerobic and aerobic biodegradability in batch experiments, viz. 70 and 86%, respectively. The highest removal efficiency achieved was for the CODss fraction, viz. 71% in the anaerobic and 85% in the combined system. Therefore, it is expected that the CODtot removal efficiency of the system can be improved, by enhancing the CODcol and CODdis, removal, i.e. applying filtration and/or adding chemicals such as adsorbents, coagulants and/or flocculants to the treatment units.
    Effects of high salinity wastewater on methanogenic sludge bed systems
    Ismail, S. ; Gonzalez-Contreras, P.A. ; Jeison, D.A. ; Lier, J.B. van - \ 2008
    Water Science and Technology 58 (2008)10. - ISSN 0273-1223 - p. 1963 - 1970.
    afvalwaterbehandeling - slib - anaërobe behandeling - zoutgehalte - natrium - granulering - korrelslib - waste water treatment - sludges - anaerobic treatment - salinity - sodium - granulation - granular sludge - anaerobic granular sludge - reactor start-up - uasb reactor - digestion - calcium - impact
    The attainable loading potentials of anaerobic sludge bed systems are strongly dependent on the growth of granular biomass with a particular wastewater. Experiments were conducted to determine the effects of high salinity wastewater on the biological and physical properties of methanogenic sludge. Sodium concentration of 5 g/L and 15 g/L were added to the influent of upflow anaerobic sludge bed (UASB) systems. After 100 days of operation, the methanogenic activity, extracellular polymeric substances (EPS), and granular strength were analyzed. The results show a high removal of organic matter but with accumulating propionate concentrations in the effluents. Meanwhile, wash-out of active methanogenic biomass in the effluent of the reactors was observed, likely as a results of the high Na+ concentrations. The rinsed biomass was characterized by a considerable specific methanogenic activity (SMA) on acetate, propionate and hydrogen as the substrates. On the other hand, results show that the SMA evolution was not affected by high salt concentrations. Also the amount and composition of extracellular polymeric substances (EPS) were similar in all sludges. However, results clearly show a sharp drop in the granule strength as a results of high Na+ concentration.
    Anaerobic biodegradation of estrogens-hard to digest
    Mes, T.Z.D. de; Kujawa, K. ; Zeeman, G. ; Lettinga, G. - \ 2008
    Water Science and Technology 57 (2008)8. - ISSN 0273-1223 - p. 1177 - 1182.
    geactiveerd slib - varkensmest - oestrogenen - afvalwaterbehandeling - anaërobe behandeling - biodegradatie - korrelslib - activated sludge - pig manure - oestrogens - waste water treatment - anaerobic treatment - biodegradation - granular sludge - waste-water treatment - removal - sewage - combination - behavior - sludge - plant
    Although many publications are available on the fate of estrone (E1), 17b-estradiol (E2) and 17a-ethynylestradiol (EE2) during aerobic wastewater treatment, little is published on their fate under strictly anaerobic conditions. Present research investigated the digestibility of E1 and EE2, using digested pig manure, granular UASB sludge, UASB-septic tank sludge and activated sludge as inocula. Besides, actual concentrations were measured in a UASB septic tank treating black water. Under anaerobic conditions E1 is reduced to E2 but the extent of this reduction depends on type of inoculum. No significant loss of the sum of E1 and E2 and of EE2 was observed. Adsorption was responsible for a 32¿35% loss of E1 and E2 from the liquid phase in the UASB septic tank and the effluent still contained considerable concentrations of respectively 4.02 mg/l and 18.79 mg/l for E1 and E2 with a large fraction present in conjugated form. No EE2 was detected in the UASB effluent
    Impact of high saline wastewaters on anaerobic granular sludge functionalities
    Jeison, D.A. ; Rio, A. del; Lier, J.B. van - \ 2008
    Water Science and Technology 57 (2008)6. - ISSN 0273-1223 - p. 815 - 819.
    calcium - afvalwater - zout water - zoutgehalte - anaërobe behandeling - slib - zuiveringsinstallaties - vergelijkend onderzoek - korrelslib - calcium - waste water - saline water - salinity - anaerobic treatment - sludges - purification plants - comparative research - granular sludge - waste-water - adaptation - digestion - reactors
    Three UASB reactors were operated at different salinity levels in order to assess the effects on the granular sludge properties. High levels of activity inhibition were observed at sodium concentrations over 7 g Na+/L, which resulted in low applicable organic loading rates and VFA accumulation in reactor effluents. However, either sludge adaptation or selection for saline resistant microorganisms occurred, which could be concluded from the observed increase in the 50% activity inhibitory concentrations of sodium during continuous flow experiments. Changes in Na+ susceptibility in time are likely to be expected when treating saline wastewaters. The latter was evidenced by the high sodium tolerance of granular methanogenic sludge coming from a full-scale industrial reactor treating such wastewater. High salinity conditions resulted in a reduced granule strength, predicting process instabilities during long term reactor operation. Batch tests showed that high sodium concentrations seemed to displace the calcium from the granular sludge, a factor known to affect anaerobic granules formation.
    High-rate anaerobic wastewater treatment: diversifying from end-of the pipe treatment to resource oriented conversation techniques
    Lier, J.B. van - \ 2008
    Water Science and Technology 57 (2008)8. - ISSN 0273-1223 - p. 1137 - 1148.
    anaërobe behandeling - energie - terugwinning - afvalwaterbehandeling - afvalwater - energiebehoud - overzichten - technologie - anaerobic treatment - energy - recovery - waste water treatment - waste water - energy conservation - reviews - technology - uasb reactor - wastewaters - sewage
    Decades of developments and implementations in the field of high-rate anaerobic wastewater treatment have put the technology at a competitive level. With respect to sustainability and cost-effectiveness, anaerobic treatment has a much better score than many alternatives. Particularly, the energy conservation aspect, i.e. avoiding the loss of energy for destruction of organic matter, while energy is reclaimed from the organic waste constituents in the form of biogas, was an important driver in the development of such systems. Invoked by the present greenhouse alert, the energy involved is nowadays translated into carbon credits, providing another incentive to further implement anaerobic technology. Anaerobic conversion processes, however, offer much more than cost-effective treatment systems. Selective recovery of metals, effective desulphurization, recovery of nutrients, reductive detoxification, and anaerobic oxidation of specific compounds are examples of the potentials of anaerobic treatment. This paper presents a survey on the state of the art of full-scale anaerobic high-rate treatment of industrial wastewaters and highlights current trends in anaerobic developments.
    Adapting UASB technology for sewage treatment in Palestine and Jordan
    Mahmoud, N.A. ; Zeeman, G. ; Lier, J.B. van - \ 2008
    Water Science and Technology 57 (2008)3. - ISSN 0273-1223 - p. 361 - 366.
    afvalwaterbehandeling - anaërobe behandeling - rioolwater - tropisch klimaat - aanpassing - jordanië - zuiveringsinstallaties - palestina - waste water treatment - anaerobic treatment - sewage - tropical climate - adjustment - jordan - purification plants - palestine - domestic sewage - low-temperature - waste-water - reactor
    High rate anaerobic technologies offer cost-effective solutions for "sewage" treatment in the temperate climate of Palestine and Jordan. However, local sewage characteristics demand amendments to the conventional UASB reactor design. A solution is found in a parallel operating digester unit that stabilises incoming solids and enriches the UASB sludge bed with methanogenic activity. The digester operational conditions were assessed by operating eight CSTRs fed with primary sludge. The results showed a high degree of sludge stabilization in the parallel digesters at SRTs10 and 15 days at process temperatures of 35 and 25°C, respectively. The technical feasibility of the UASB-digester combination was demonstrated by continuous flow pilot-scale experiments. A pilot UASB reactor was operated for 81 days at 6 hours HRT and 15°C and was fed with raw domestic sewage. This period was subsequently followed by an 83 day operation period incorporating a parallel digester unit, which was operated at 35°C. The UASB-digester combination achieved removal efficiencies of total, suspended, colloidal and dissolved CODs of respectively 66, 87, 44 and 30%. Preliminary model calculations indicated that a total reactor volume of the UASB-digester system corresponding to 8.6 hours HRT might suffice for sewage treatment in Palestine
    Anaerobic wastewater treatment and membrane filtration: a one night stand or a sustainable relationship?
    Jeison, D.A. ; Lier, J.B. van - \ 2008
    Water Science and Technology 57 (2008)4. - ISSN 0273-1223 - p. 527 - 532.
    afvalwaterbehandeling - vervuiling door afzetting - membranen - anaërobe afbraak - filtratie - anaërobe behandeling - deeltjesgrootte - slib - bioreactoren - waste water treatment - fouling - membranes - anaerobic digestion - filtration - anaerobic treatment - particle size - sludges - bioreactors - reactors
    Several anaerobic membrane bioreactors (AnMBR) were operated, under various conditions, applying different reactor configurations. Applicable fluxes were strongly determined by the physical properties of the sludge present in the reactors. Results show that particle size is a key determining factor for the attainable fluxes. Under thermophilic conditions, small sludge particle size was observed, resulting in low critical fluxes reaching 6¿7 L/m2 h for the submerged configuration and acidified substrate. In contrast, under mesophilic conditions critical fluxes of 20 L/m2 h were obtained. The acidification level also showed a strong effect. Under thermophilic conditions, the presence of a significant fraction of non-acidified organic matter induced the growth of suspended acidogenic biomass that seriously affected the applicable fluxes, both in submerged and side-stream configurations. Under all conditions tested cake formation showed to be the limiting factor determining the applicable fluxes. Only low levels of irreversible fouling were observed. Due to technical and economical considerations, most interesting perspectives for the application of AnMBR are expected with the treatment of high-strength particulate wastewaters, and with extreme wastewaters characterised by high temperature, salinity, etc.
    Water en grondstoffen terugwinnen met anaerobe zuivering; is de historische veronachtzaming volledig achterhaald?
    Lier, J.B. van - \ 2007
    Spil 2007 (2007)237-238. - ISSN 0165-6252 - p. 23 - 26.
    afvalwaterbehandeling - waterzuivering - anaërobe behandeling - waste water treatment - water treatment - anaerobic treatment
    Uitleg waarom anaërobe zuiveringstechnologie de voorkeur verdient. Tevens wordt de betekenis van Wageningen UR bij het vermarkten van deze techologie genoemd
    Anaerobie is veel meer dan louter afvalwaterzuivering
    Lier, J.B. van - \ 2007
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 40 (2007)10. - ISSN 0166-8439 - p. 12 - 13.
    anaërobe behandeling - afvalwaterbehandeling - afvalwater - waterzuivering - duurzaamheid (sustainability) - watergebruik - anaërobie - anaerobic treatment - waste water treatment - waste water - water treatment - sustainability - water use - anaerobiosis
    De wereldwaterproblematiek vraagt grote aandacht. De millenniumdoelstellingen, die de Verenigde Naties in dit verband opgesteld hebben, zijn al diverse malen, ook in dit blad, naar voren gebracht en zullen voortdurend aandacht en inzet blijven vragen. Belangrijke vraag daarbij is hoe die doelstellingen bereikt moeten worden, zowel financieel als technisch. Critici zeggen dat ons systeem van waterbeschaving verkwistend is. In onze huizen verdunnen we de menselijke ontlasting met een factor honderd en meer, waardoor een immens afvalwaterprobleem ontstaat en bovendien de kosten van de preventieve verwijdering van ziektekiemen uit dat water niet meer in verhouding staan tot die van het behandelen van patiënten. Onze aanpak is een slecht voorbeeld voor ontwikkelingslanden, zeggen zij. De anaerobe afvalwaterbehandeling is een duurzaam alternatief dat volgens hen veel meer aandacht verdient. Reden voor een gesprek met prof. dr. ir. Jules van Lier, hoogleraar anaerobe afvalwaterbehandeling aan Wageningen Universiteit & Researchcentrum, die in november 2006 zijn inaugurele rede hield met als titel 'Meervoudig watergebruik, van last naar lust'
    Microbial community analysis in sludge of anaerobic wastewater treatment systems : integrated culture-dependent and culture-independent approaches
    Roest, C. - \ 2007
    Wageningen University. Promotor(en): Willem de Vos; Fons Stams, co-promotor(en): A.D.L. Akkermans; Hauke Smidt. - [S.l.] : S.n. - ISBN 9789085048398 - 159
    rioolslib - micro-organismen - anaërobe omstandigheden - afvalwaterbehandeling - anaërobe behandeling - stedelijk afvalwater - sewage sludge - microorganisms - anaerobic conditions - waste water treatment - anaerobic treatment - municipal wastewater
    The need for clean water is increasing and anaerobic wastewater treatment can be used as a cost-effective solution for purification of organically polluted industrial waste streams. This thesis presents results from microbiological investigations of several full-scale and lab-scale anaerobic wastewater treatments systems. Anaerobic wastewater treatment has gained popularity and is now one of the key technologies in environmental biotechnology. However, knowledge of the microbial community structure – function relationships is limited. A combination of cultivation-dependent and cultivation-independent techniques can be used to improve this knowledge. In this thesis, batch serial dilution incubations from a methanol-fed lab-scale thermophilic (55°C) methanogenic bioreactor indicated that syntrophic interspecies hydrogen transfer-dependent methanol conversion is at least equally important as direct methanogenesis in this lab-scale reactor. A direct methanol-utilizing Methanomethylovorans hollandica-related strain was detected up to a 108-fold dilution, while Thermodesulfovibrio relatives and Methanothermobacter thermoautotrophicus strains were found till 109–fold dilutions in the presence of H2/CO2. Microbial diversity was further evaluated in two expanded granular sludge bed reactors fed with increasing oleic acid loading rates. The archaeal community in the reactor inoculated with granular sludge stayed quite stable and active, whereas the relative abundance of Methanosaeta-like organisms gradually decreased in the reactor inoculated with suspended sludge when oleate loads were increased to 8 kg of chemical oxygen demand m-3 day-1. Desulfomicrobium and Methanobacterium were found to dominate the start-up of a full-scale synthesis gas fed gas-lift reactor treating metal and sulphate rich wastewater. Most Probable Number (MPN) counts confirmed that heterotrophic sulphate reducing bacteria (SRB) were dominant (1011-1012 cells/g VSS) compared to homoacetogens (105-106 cells/g VSS) and methanogens (108-109cells/g VSS). Methanogens can still persist in sulphate-reducing bioreactors with short sludge retention time, since competition for hydrogen is determined by Monod kinetics and not by hydrogen threshold values. The microbial community in a full-scale upflow anaerobic sludge blanket reactor treating paper mill wastewater operated at 37°C was relatively stable over a period of 3 years as indicated by a high similarity (>75%) of denaturing gradient gel electrophoresis profiles of 16S ribosomal RNA gene fragments. Batch incubations at different temperatures resulted in microbial community changes. While the archaeal community composition differed significantly between incubations at 45 and 55°C, the bacterial composition changed between 37 and 45°C. Overall the bacterial community was dominated by Firmicutes (68% of the clones) and Delta-Proteobacteria (17% of the clones). A sequential degradation of first butyrate and then propionate at 37°C was linked to strong presence of Syntrophomonas sp. and Desulfobulbus propionicus, respectively. MPN series allowed estimating the number of micro-organisms per ml sludge that could use propionate without sulphate (109), propionate and sulphate (105), butyrate without sulphate (108), butyrate with sulphate (105), glucose (109) and H2/CO2 (1010). Archaea were mainly dominated by Methanosaeta, but also Crenarchaeota-relatives were identified. Bacterial clone sequences were related to a variety of different known species, with expected functions in anaerobic digestion like fermentative bacteria, syntrophic short chain fatty acids oxidisers and SRB. However, about 80% of the clones was similar to sequences in the database without close cultured relatives, but many of these appeared to be present in anaerobic environments. It is important to improve knowledge of these unknown micro-organisms and fast accurate monitoring and identification could be instrumental in realising this. Therefore, a pilot macro-array was developed and tested. It appeared that combining probes generated by PCR amplification of the V1 and V6 variable regions of the 16S rRNA gene provided accurate differentiation of closely related organisms. The integrated application of molecular and cultivation dependent analyses of microbiota structure and function of a broad variety of anaerobic wastewater treatment systems described in this thesis has been used to improve insight of the ecophysiology in such reactors. Some general commonalities of anaerobic systems have been found, but also system-specific characteristics. This provides potential identification of general and system-specific indicator populations, allowing improved diagnostics and reactor predictability.
    Sulfate reduction at low pH in organic wastewaters
    Lopes, S.I.C. - \ 2007
    Wageningen University. Promotor(en): Cees Buisman, co-promotor(en): P. Lens; M.I. Capela. - [S.l.] : S.n. - ISBN 9789085047636 - 244
    afvalwaterbehandeling - ph - verzuring - sulfaten - anaërobe behandeling - sulfaatreductie - waste water treatment - ph - acidification - sulfates - anaerobic treatment - sulfate reduction
    The objective of the research described in this thesis was to investigate the operational window of dissimilatory sulfate reduction at low pH (6, 5 and 4) during the acidification of organic wastewaters. High sulfate reduction efficiencies at low pH are desirable for a more sustainable operation of acidification reactors in a two-phase wastewater treatment system, as pH control requires less caustic and/or the effluent recirculation from the second (methanogenic) reactor can be skipped. The low pH would also facilitate the removal of sulfide by stripping, as the fraction of gaseous sulfide increases with decreasing pH
    Anaerobic membrane bioreactors for wastewater treatment: feasibility and potential applications
    Jeison, D.A. - \ 2007
    Wageningen University. Promotor(en): Jules van Lier. - [S.l.] : S.n. - ISBN 9789085046998 - 199
    bioreactoren - anaërobe behandeling - afvalwaterbehandeling - membranen - biologische filtratie - biomassa - vervuiling door afzetting - bioreactors - anaerobic treatment - waste water treatment - membranes - biological filtration - biomass - fouling
    Biomass retention is a necessary feature for the successful application of anaerobic digestion for wastewater treatment. Biofilms and granule formation are the traditional way to achieve such retention, enabling reactor operation at high biomass concentrations, and therefore at high organic loading rates. Membrane filtration represents an alternative way to achieve biomass retention. In membrane bioreactors, complete biomass retention can be achieved, irrespective of cells capacity to form biofilms or granules. Membrane bioreactor systems represent then a promising technology for those conditions where biomass aggregation cannot be ensured, or when an effluent completely free of suspended solids is of interest. In the present thesis the feasibility of anaerobic membrane bioreactors (AnMBR) is described, under a wide range of conditions and reactor configurations
    Volatile organic sulfur compounds in anaerobic sludge and sediments: biodegradation and toxicity
    Leerdam, R.C. van; Bok, F.A.M. de; Lomans, B.P. ; Stams, A.J.M. ; Lens, P.N.L. ; Janssen, A.J.H. - \ 2006
    Environmental Toxicology and Chemistry 25 (2006)12. - ISSN 0730-7268 - p. 3101 - 3109.
    microbiële afbraak - slib - sediment - anaërobe behandeling - afvalwaterbehandeling - sulfaten - thiolen - reductie - sulfaat - methanol - biodegradatie - microbial degradation - sludges - sediment - anaerobic treatment - waste water treatment - sulfates - thiols - reduction - sulfate - methanol - biodegradation - fresh-water sediments - dimethyl sulfide - membrane bioreactor - waste air - methanethiol - degradation - inhibition - removal - ph - methanogens
    A variety of environmental samples was screened for anaerobic degradation of methanethiol, ethanethiol, propanethiol, dimethylsulfide, and dimethyldisulfide. All sludge and sediment samples degraded methanethiol, dimethylsulfide, and dimethyldisulfide anaerobically. In contrast, ethanethiol and propanethiol were not degraded by the samples investigated under any of the conditions tested. Methanethiol, dimethylsulfide, and dimethyldisulfide were mainly degraded by methanogenic archaea. In the presence of sulfate and the methanogenic inhibitor bromoethane sulfonate, degradation of these compounds coupled to sulfate reduction occurred as well, but at much lower rates. Besides their biodegradability, also the toxicity of methanethiol, ethanethiol, and propanethiol to methanogenesis with methanol, acetate, and H2/CO2 as the substrates was assessed. The 50% inhibition concentration of methanethiol on the methane production from these substrates ranged between 7 and 10 mM. The 50% inhibition concentration values of ethanethiol and propanethiol for the degradation of methanol and acetate were between 6 and 8 mM, whereas hydrogen consumers were less affected by ethanethiol and propanethiol, as indicated by their higher 50% inhibition concentration (14 mM). Sulfide inhibited methanethiol degradation already at relatively low concentrations: methanethiol degradation was almost completely inhibited at an initial sulfide concentration of 8 mM. These results define the operational limits of anaerobic technologies for the treatment of volatile organic sulfur compounds in sulfide-containing wastewater streams
    Integrated treatment of tapioca processing industrial wastewater based on environmental bio-technology
    Huynh Ngoc Phuong Mai, - \ 2006
    Wageningen University. Promotor(en): Gatze Lettinga, co-promotor(en): N.T. Viet. - [S.l. ] : S.n. - ISBN 9789085044413 - 180
    afvalwaterbehandeling - tapioca - voedselverwerking - anaërobe behandeling - rioolslib - vietnam - fabrieksafvalwater - waste water treatment - tapioca - food processing - anaerobic treatment - sewage sludge - vietnam - factory effluents
    Tapioca processing wastewater containing high COD (9,630-13,760 mg/L), BOD (7,280-11,510 mg/L), SS (450-1,850 mg/L), total nitrogen (291-355 mg/L) total phosphorus (39-73 mg/L) and low pH (3.4-4.6) are one of the major causes of severe pollution to receiving source in South Vietnam. Based on the characteristics of tapioca processing wastewater, biological treatment processes are selected for study. In which the UAF, UASB, aeration tank and pond system are in series. For this treatment technology, the UAF reactor is used as pre-treatment for reducing of SS. The SS removal efficiencies ranged from 67-82%, equivalent to influent SS decreased from 450-1,850 mg/L to 148-290 mg/L. The core of treatment system is the UASB-reactor, which is responsible for the removal of organic matter. The OLR of UASB-reactor can achievedto 42 kgCOD/m 3 .d with HRT8.3-8.4 hours. The influent COD decreased from 10,498-14,330 mg/L to 1,082-2,178 mg/L, equivalent with treatment efficiencies ranged from 82.5-90.7%. The aeration tank and pond system are used as post-treatment. They take responsibility for the remainder of organic matter, nitrogen and phosphorus removal. With the HRT around 6-8 hours for aeration tank and 6-7 days for pond system, the effluent COD, total nitrogen and total phosphorus ranged from 78-94 mg/L, 4.5-5.7 mg/L, 7.3-7.9 mg/L, respectively. In the UASB-reactor, the granular sludge was observed after 20 days of operating at OLRof 6 kgCOD/m 3 .d. The study also showed that nutrients and trace elements are necessary for tapioca wastewater treatment using UASB-reactor, but only for start-up period, when OLR lowerthan 20 kgCOD/m 3 .d. The UASB-reactor was able to stand a shock load as the COD concentration three times higher than normal, in 24 hrs stretches, without any damage and the completed recovery took 2-3 days.The investigateon cyanide toxicity showed that cyanide exerts a distinct toxicity, in particular on the hydrolysis process of tapioca starch particles. Hence, hydrolysis of these particles was completed within 2 days in the control experiment (using 2g starch particles and 2 gVSS/L in the experiment conducted at 30 o C), while at a high cyanide concentration of 120 mgCN - /L it took up to 6 days. But compared to the hydrolysis process, the acidification process is much less affected by cyanide; acidification always proceeded immediately after hydrolysis of the starch particles. The experiments of reduction the cyanide toxicity showed that sulphide ions do not reduce the toxicity of cyanide through the formation of thiocyanate, but instead reinforce the toxicity of cyanide. And the addition of Fe 2+ significantly reduces the toxicity of cyanide on the hydrolysis and methanogenesis through the formation of the ferro-cyanide complex, but it does not stimulate the degradation of cyanide.The conclusions of the research showed that the solution comprising the implementation of the AnWT-technology combined with aerobic post-treatment, clearly demonstrates the big benefit of the energy cost savings and resource conservation together with its feasibility to meet really extremely severe discharge standards. It also shows how strong returns can be generated for investors using CDM. The estimate shows that the required treatment system with a capacity of 2,000 m 3 /d will produce 4,200 - 6,200 m 3 biogas per day (>60 % methane gas), which is equivalent to 2,600 - 3,800 liters of FO per day. And energy cost savings to the plant are estimated at 850 - 1,260 US$ per day.
    Microbial aspects of synthesis gas fed bioreactors treating sulfate and metal rich wastewaters
    Houten, B.H.G.W. van - \ 2006
    Wageningen University. Promotor(en): Fons Stams, co-promotor(en): Hauke Smidt. - Wageningen : - ISBN 9789085043973 - 112
    afvalwaterbehandeling - bioreactoren - anaërobe behandeling - methanobacteriaceae - sulfaat reducerende bacteriën - waste water treatment - bioreactors - anaerobic treatment - methanobacteriaceae - sulfate reducing bacteria

    The use of synthesis gas fed sulfate-reducing bioreactors to simultaneously remove both oxidized sulfur compounds and metals shows great potential to treat wastewaters generated as a result of flue gas scrubbing, mining activities and galvanic processes. Detailed information about the phylogenetic and functional composition of the microbial communities within these bioreactors however was limited prior of this study. In order to understand and enable the effective control of performance of these bioreactors, an increased understanding of the microbial aspects of sulfate-reducing synthesis gas fed bioreactorsis required. 16S rRNA gene analysis demonstrated that the bacterial communities were dominated by the sulfate-reducing genera Desulfovibrio and Desuifomicrobium. Archaeal communities were comprised of microorganisms belonging to the methanogenic genus Methanobacterium. Synthesis gas fed bioreactors however were also able to sustain a diverse bacterial community, not limited to hydrogenotrophic microorganisms. Abundant 16S rRNA clones were also found which showed affiliation to the proteolytic microorganism Proteiniphilum acetatigenes and uncultured Thermotogales, while other clones clustered within the Chloroflexi subphylum I. A putative role for these organisms as scavengers of dead microbial cells was hypothesized. Due to the relatively short sludge retention time in these bioreactors hydrogen threshold concentrations are not reached, and instead Monod kinetic parameters controls hydrogen competition. As a result of fluctuations in operating conditions at full-scale a continuous state of hydrogen limitation may not be reached, resuiting in suppression of methanogenesis being a slow process. Limiting the carbon dioxide feed rate appeared to be a very effective selective tool to control methanogenesis at full scale, although it did not lead to the complete removal of methanogens from the system.

    Heterotrophic SRB and homoacetogens were able to coexist when H2, CO2 and sulfate were supplied as the sole substrates as they were not limited by the same substrate; homoacetogens being hydrogen limited, while heterotrophic SRB were acetate limited. This consortium was able to compete effectively with methanogens, as the growth rate of even autotrophic methanogens is negatively affected by the lack of acetate. Even though homoacetogens are reported to have a high hydrogen threshold and a low ?™, they posses a high affinity (K5), which gives them a kinetic advantage over methanogens with intermediate growth rates (0.15 -0 .50 day"1) at 300CAs growth of methanogens is affected by the availability of acetate, limiting the addition of acetate to the feed of synthesis gas fed bioreactors may provide an additional tool to selectively control methanogenesis. In conclusion,the increased understanding of the microbial communities ofsu!fate-reducing synthesis gas fed bioreactors has provided greater insight into the competition for hydrogen and possibilities to control unwanted methanogenesis. Furthermore, the performance and stability of a full-scale reactor over a period of 128 weeks, demonstrate that this technology can be used successfully at full scale to treat sulfate and metal rich wastewaters.

    The anaerobic treatment approach towards a more sustainable and robust environemnetal protection
    Lettinga, G. - \ 2005
    Water Science and Technology 52 (2005)1-2. - ISSN 0273-1223 - p. 1 - 11.
    afvalwaterbehandeling - biologische behandeling - milieubescherming - anaërobe behandeling - spijsvertering - korrels - waste water treatment - biological treatment - environmental protection - anaerobic treatment - digestion - granules - waste-water treatment - sludge bed reactor - removal - uasb
    Anaerobic biological degradation processes (AnDe), when properly integrated with complementary biological and physical methods, constitute the ideal route to a sustainable protection of the life environment. However unfortunately for a smooth implementation of AnDe-processes drastic conceptual innovations are urgently needed in the field of environment protection; the present highly centralized approach in the public sanitation sector (CENSA) need to be substituted by a concept that focuses on optimal decentralization, problem prevention, self-sufficiency, resource recovery and reuse, with coupling to agriculture practices at or nearby the location (DESAR). Although a variety of excellent DESAR-based systems already are available and anaerobic digestion and treatment methods have found successful full-scale application for waste and wastewater treatment, there still is potential to improve these systems. Interesting questions to be elucidated are the effect of trace elements and macro-nutrients, the sludge immobilization phenomenon and the effect of environmental factors like temperature, pressure, mixing. Therefore tentatively a lot of challenging interdisciplinary research is waiting to attain further profitable innovations. Keywords Granular sludge-growth and manipulation; innovation; nutrients; paradigm; self-phasing; trace elements; valorization
    Anaerobic digestion of concentrated wastewater in DESAR concept
    Kujawa, K. ; Zeeman, G. - \ 2005
    Utrecht : Stowa (STOWA rapport 14)
    waste water treatment - anaerobic treatment - waste water - separation - water reuse - collection - afvalwaterbehandeling - anaërobe behandeling - afvalwater - scheiding - hergebruik van water - verzamelen
    De haalbaarheid van anaërobe vergisting voor de behandeling van geconcentreerd zwartwater en keukenafval en zijn effect op het totale DESAH concept was de hoofdvraag van dit onderzoek. Deze haalbaarheid is uitgedrukt in: - het rendement dat kan worden verkregen in verschillende vergistingconfiguraties bedreven onder verschillende procesomstandigheden; - de kwaliteit en het hergebruikpotentieel van de verkregen producten. Het DESAH concept kent vele variatiemogelijkheden en daarmee is er geen universeel DESAH concept dat past in elke situatie. Er zijn echter elementen die identiek zijn voor alle scenario’s. Eén element is dat afvalwaterstromen gescheiden worden ingezameld op basis van bijvorbeeld de vervuilingsgraad, het type vervuiling en het hergebruikpotentieel van grondstoffen. Drie soorten grondstoffen zijn te onderscheiden: bio-energie (via de omzetting van organisch materiaal), nutrienten (stikstof, fosfaat en kalium) en water (via een geavanceerde nabehandeling van minder vervuilde afvalwaterstromen). De behandeling wordt zo geselecteerd dat het hergebruikpotentieel wordt behouden.
    Thermophillic treatment by anaerobic granular sludge as an effective approach to accelerate the electron transfer and improve the reductive decolorization of azo dyes in bioreactors
    Santos, A.B. dos; Traverse, J. ; Cervantes, F.J. ; Lier, J.B. van - \ 2005
    Water Science and Technology 52 (2005)1-2. - ISSN 0273-1223 - p. 363 - 369.
    ontkleuring - temperatuur - textielindustrie - kleurstoffen (dyes) - azoverbindingen - afvalwaterbehandeling - anaërobe behandeling - slib - decolorization - temperature - textile industry - dyes - azo compounds - waste water treatment - anaerobic treatment - sludges - redox mediators - reactor - transformation - aqds
    The effects of temperature, hydraulic retention time (HRT), and the redox mediator, thraquinone- 2,6-disulfonate (AQDS), on electron transfer and subsequent reductive decolorization of dyes rom textile wastewater was assessed in mesophilic and thermophilic anaerobic bioreactors. The results clearly show that compared to mesophilic anaerobic treatment, thermophilic treatment at 55 8C is an effective approach for increasing the electron transfer capacity in bioreactors, and thus improving the decolorization rates. At an HRT of 2.5 h and in the absence of AQDS, the color removal was 5.3-fold higher at 55 8C compared to 30 8C. Furthermore, similar decolorizations were found at 55 8C between the AQDS-free and AQDSsupplemented reactors, whereas a significant difference (up to 3.6-fold) on dye reduction occurred at 30 8C. Keywords Azo dye; color removal; electron transfer; anaerobic treatment; mesophilic; thermophilic
    The effect of operational conditions on the performance of UASB reactors for domestic wastewater treatment
    Leitao, R. ; Silva-Filho, J.A. ; Sanders, W.T.M. ; Haandel, A.C. van; Zeeman, G. ; Lettinga, G. - \ 2005
    Water Science and Technology 52 (2005)1-2. - ISSN 0273-1223 - p. 299 - 305.
    afvalwaterbehandeling - anaërobe behandeling - prestatieniveau - verwijdering - chemisch zuurstofverbruik - slib - waste water treatment - anaerobic treatment - performance - removal - chemical oxygen demand - sludges
    In this investigation, the performance of Upflow Anaerobic Sludge Blanket (UASB) reactors treating municipal wastewater was evaluated on the basis of: (i) COD removal efficiency, (ii) effluent variability, and (iii) pH stability. The experiments were performed using 8 pilot-scale UASB reactors (120 L) from which some of them were operated with different influent COD (CODInf ranging from 92 to 816 mg/L) and some at different hydraulic retention time (HRT ranging from 1 to 6 h). The results show that decreasing the CODInf1 or lowering the HRT, leads to decreased efficiencies and increased effluent variability. During this experiment, the reactors could treat efficiently sewage with concentration as low as 200 mg COD/L. They could also be operated satisfactorily at an HRT as low as 2 hours, without problems of operational stability. The maximum COD removal efficiency can be achieved at CODInf exceeding 300 mg/L and HRT of 6 h.
    Effect of operational variables on nitrogen transformations in duckweed stabilization ponds
    Caicedo Bejarano, J.R. - \ 2005
    Wageningen University. Promotor(en): H.J. Gijzen, co-promotor(en): N.P. van der Steen. - [S.l.] : S.n. - ISBN 9789085041627 - 163
    spirodela polyrhiza - stikstof - stikstofbalans - nitrificatie - anaërobe behandeling - algen - bezinkingsvijvers - spirodela polyrhiza - nitrogen - nitrogen balance - nitrification - anaerobic treatment - algae - stabilization ponds
    There is a diversity of conventional technologies available for removal of pollutants from wastewater. Most of these technologies are aerobic alternatives with high construction cost and high energy consumption and require skilled personal for operation and maintenance. As a consequence, only countries with a high gross national product (GNP) can afford these options. Where these technologies were introduced in developing countries, in most cases these could not be operated sustainably, leading to loss of investments and continued water resource contamination. Extensive investments in wastewater treatment plants world-wide during the last decades have greatly reduced the organic loading of receiving water bodies in high GNP countries. Only recently, many of these plants were appropriated to remove nitrogen and phosphorus. The increasing use of chemical fertilizer may cause high levels of eutrophication in water bodies, which may induce algae blooms resulting in strong fluctuations in oxygen concentration. Oxygen depletion causes fish kill as well as odor problems.

    The situation in countries with a low GNP is worse than in the developed world. The unequal expansion of water supply coverage compared to the expansion in wastewater and sanitation services leads to increased contamination of surface and ground waters. The general trend is to use conventional WWT systems for big cities, but for medium and small sized cities non-conventional systems are often considered. Therefore, there is an urgent need to develop and improve low cost technologies for wastewater treatment that are within the economic and technological capabilities of developing countries. In countries like Colombia it is very common that the regulation controls mainly the removals of organic matter and suspended solids. Other parameters like nitrogen, phosphorus, pathogens, micro-contaminants are also crucial and need to be addressed. This makes a response via conventional technologies very expensive, and for developing regions in fact unachievable. It would be ideal if new technologies can provide besides the removal of organic matter and solids, resource recovery like the generation of biogas (energy production) or high quality biomass (animal fodder). At the moment, no technological packages appear to be readily available.

    Experience has shown that no single technology can offer an optimum treatment for the different components to be treated in wastewater or to recover them as valuable resources. Therefore an adequate combination of different technologies in an integrated system could convert a wastewater treatment into an attractive sustainable system. For example UASB reactor and duckweed ponds are relatively low cost technologies and their combination offers several advantages. Firstly, anaerobic treatment will reduce considerably the organic matter in the wastewater and convert it into methane, which can be used as a source of renewable energy. Secondly, the effluents of anaerobic treatment could be post-treated to meet discharge standards in duckweed ponds for nutrient recovery in the form of high quality biomass.At this point three valuable products can be listed: biogas for use as an energy source, biomass that can be used for aquaculture or animal feed and treated effluent that can be re-used in irrigation. A system that generates such by-products increases the feasibility and sustainability of pollution control programs. Furthermore, the products may help to address the increasing need for food production in the world. 

    The development of duckweed pond technology has been concentrated on the study of the processes occurring within the ponds, with respect to organic matter, nitrogen, phosphorus and pathogen removal and the corresponding mechanisms. Further research is needed in order to have a good control of effluent nitrogen levels. There are still important questions to be answer like how to maximize nitrogen recovery via duckweed production, how to get good effluent levels depending on effluent reuse. If the effluent is going to be used in crop irrigation, to reduce nitrogen effluent concentration to 15-20 mg l -1 will be enough. If the effluent is going to be discharge in surface waters the nitrogen level would have to be reduced as much as possible. Therefore it is important to study how the design and combination of technologies could generate the required nitrogen effluent levels. The present work was focus on the study of the effect of different operational variables, like the effect of anaerobic pre-treatment, the combination of algae and duckweed ponds, the effect of pond depth on nitrogen transformation and removals.

    The effect of anaerobic pre-treatment on environmental and physicochemical characteristics of duckweed stabilization ponds was studied in Chapter 2 .The environmental and physicochemical conditions affect both plant growth and microbiological treatment processes in the system. Two series of continuous-flow pilot plants, composed of seven ponds in series each, were operated side by side. One system received artificial sewage with anaerobic pre-treatment, while the other system received the same wastewater without anaerobic pretreatment. pH, temperature, dissolved oxygen, alkalinity, conductivity, biochemical oxygen demand, total and ammonium nitrogen, nitrites and nitrates, and phosphorus were monitored under steady state conditions. It was found that pH levels were very stable in both systems with and without anaerobic pretreatment. Vertical temperature gradients were present during daytime but not as strong as they may occur in conventional stabilization ponds. Oxygen levels were significantly higher in the duckweed system with anaerobic pretreatment, especially in the top layer. (up to 2 mg O 2 l -1 ) than in the system without pretreatment (up to 1.2 mg O 2 l -1 ). Nevertheless, aeration rates were low in both systems. Both systems were efficient in removing organic matter. The system without pretreatment obtained 98% of BOD 5 removal in pond 4, so 12 days of retention time will be sufficient to reach high organic matter removal. The system with pretreatment obtained also 98% BOD 5 removal (92% in UASB reactor). In this case the duckweed ponds will serve as a polishing step for remaining organic matter. Nutrient removals were 37-48% for nitrogen and 45-50 % for phosphorus in the lines with and without pretreatment respectively.

    The main form of nitrogen in anaerobic effluent is ammonium. This is the preferred nitrogen source for duckweed, but at high levels it may become inhibitory to the plant. Renewal fed batch experiments at laboratory scale were performed (Chapter 3 ) to assess the effect of total ammonia (NH 3 + NH 4+ ) nitrogen and pH on the growth rate of the duckweed Spirodela polyrrhiza. The experiments were performed at different total ammonia nitrogen concentrations, different pH ranges and in three different growth media. The inhibition of duckweed growth by ammonium was found to be due to a combined effect of ammonium ions (NH 4+ ) and ammonia (NH 3 ), the relative importance of each one depending on pH.

    The effect of anaerobic pre-treatment on the performance of a duckweed stabilization pond system was assessed in a pilot plant located in the Ginebra Research Station-Colombia (Chapter 4). The pilot plant consisted of two lines of seven duckweed ponds in series. One line received de-gritted domestic wastewater and the other received effluent of a 250 m 3 Up-flow Anaerobic Sludge Blanket (UASB) reactor, treating the same wastewater. Both lines were operated at a total hydraulic retention time of 21 days.The systems were monitored for temperature, pH, oxygen, biochemical oxygen demand, chemical oxygen demand, total suspended solids, total phosphorus, biomass production, and different forms of nitrogen. No effect of anaerobic pretreatment was observed on pH and temperature in the two systems. Oxygen concentrations were higher in the system with UASB reactor. Although both systems complied with the Colombian regulation for BOD removal (> 85%)pretreatment with UASB reactor may contribute to the reduction of area requirement for the stabilization ponds. Effluent quality in terms of total suspended solids was excellent, i.e. 9 ± 2 and 4 ± 1 mg l -1 in the system with and without pre-treatment, respectively. Total nitrogen removals were 63 % and 68% and phosphorus removals were 24% and 29% in the system with and without pre-treatment, respectively. The differences between the two systems were found not to be significant. Duckweed biomass production was in the range of 54-90 g m -2 -d -1 (fresh weight) in the system with pre-treatment and 36-84 g m -2 -d -1 in the system without pre-treatment. Total biomass productions were significantly different at 92% level of confidence. Protein content was 35.1% and 36.6% for the system with and without pre-treatment, respectively.Nitrogen removal is nowadays one of the most important effluent treatment objectives because of the serious pollution problems it causes to the environment. How nitrogen is transformed and removed in duckweed ponds was studied and nitrogen balances were established (Chapter 5). The experimental system was the same as in the previous chapter. Ammonia volatilization was found to be not an important removal mechanism in duckweed ponds (less than 1%). Removal by sedimentation was also low at 2.1% and 4.7% for the systems with and without anaerobic pre-treatment, respectively. Instead, denitrification was found to be the most important removal mechanism (42% and 48%), followed by duckweed biomass up-take (15.6% and 15.1%). Average nitrogen biomass up-take rates were 199 mg N m -2 d -1 and 193 mg N m -2 d -1 for the system with and without pre-treatment, respectively. Nitrification rates were in the range of112 - 1190 mg N m -2d -1 and 58-1123 mg N m -2 d -1 for the system with and without anaerobic pretreatment respectively. Denitrification rates were in the range of 112 - 937 mg N m -2 d -1 and 59 - 1039 mg N m -2 d -1 for the system with and without pre-treatment respectively. The configuration of the system, in particular the down and up flow pattern seemed to have an important stimulating effect on denitrification rates, probably by causing alternative exposure of the pond water to aerobic and anoxic conditions.Although the potential of duckweed ponds for removing carbonaceous and suspended material from wastewater has been demonstrated, the system could be further optimized for nitrogen removal. The effect of introducing algae-ponds (aerobic zones) into a series of duckweed stabilization ponds on nitrification and denitrification (Chapter 6 ) was studied in two consecutive phases. During the first phase, the seven ponds of the pilot plant were fully covered with duckweed (Spirodela polyrrhiza). Before the start of the second phase, the duckweed cover was removed from ponds 1 and 3, with a view to allow algae growth in the 'open' ponds. The feed of the duckweed pond system consisted of the effluent of a real scale UASB reactor, which treated domestic wastewater from Ginebra-Colombia. The system was operated with a continuous flow to produce a hydraulic retention time (HRT) of 3 days per pond and a total HRT of 21 days. Effluent total nitrogen was significantly different in the two phases, with 13.8± 2.9 mg TN l -1 (63 % removal) and 3.7±1.5 mg TN l -1 (90%) for first and second phase, respectively.Denitrification was the most important removal mechanism during both phases, and amounted to 43.5 % and 76.2 % of influent nitrogen, in first and second phase, respectively. Ammonia volatilization and sedimentation were insignificant processes for nitrogen removal in both phases. Nitrification played an important role in nitrogen transformations in the duckweed systems and it was favored by the introduction of aerobic zones in ponds 1 and 3. Denitrification also played a key role in nitrogen transformations and removal. Despite the presence of oxygen in the water column, denitrification occurred, probably due to the anaerobic microenvironment of system biofilms. Higher nitrogen removal might be obtained in duckweed pond systems through the introduction of aerobic zones in early stages of the system. Where effluents cannot be reused for crop irrigation, strict nitrogen effluent criteria can be met using hybrid duckweed-algal ponds at considerably shorter hydraulic retention time compared to fully duckweed covered systems.

    The effect of pond depth on nitrogen removal in duckweed stabilization ponds was studied in Chapter 7. The pilot plant consisted of two lines with seven duckweed ponds in series, with different depths and fed with effluent of a laboratory scale UASB reactor. Three experimental conditions were studied: DSP1 with pond depth 0.7 m and HRT= 21 days, DSP2 with pond depth 0.4 m and HRT = 12 days, and DSP3 with pond depth 0.4 m and HRT = 21 days. The systems were monitored for pH, temperature and oxygen profiles, organic matter removal (BOD 5 ), nitrogen transformations, biomass production and biomass nitrogen content. Average total nitrogen removal rates were 598 mg N m -2 d -1 for DSP 1, 589 mg N m -2 d -1 for DSP 2 and 482 mg N m -2 d -1 for DSP 3. In spite of the lower nitrogen removal rate in DSP 3, it had higher removal efficiency (44 %, 43 % and 62 % for DSP 1, 2 and 3 respectively) due to the lower surface loading rate in this system. This shows that using the percentage of removal as a parameter for comparison should be done with care and the operational parameters of the compared systems should be taken into account. Denitrification was the most important nitrogen removal mechanism for the three DSPs. Nitrogen removal via biomass production was the second most important removal mechanism for the three experiments. Pond depth does not seem to determine nitrification or denitrification. Nitrification seems to be related to surface organic loading rate, while denitrification was related to BOD availability. The comparison between two pond systems with different depth, but operated at the same hydraulic surface loading rate (DSP 1 and 2) showed similar nitrogen removals in the shallower system as in the deeper system. This suggests that duckweed pond system could be designed with shallow depth without affecting surface loading and nitrogen removal efficiency. Nitrogen removal appeared to be governed by surface loading rate rather than by hydraulic retention time.

    Most of the research so far has been performed at laboratory or pilot scale. In the process of technology-development it is important to test findings at full scale. In Chapter 8 , the performance of a full scale duckweed pond was compared with a full scale algae pond treating effluent of a UASB reactor operated under similar conditions of climate, configuration, wastewater composition and loading rate. The real scale experimental system was composed of two continuous flow channels. One operated as an algae pond and the other as a duckweed pond ( Spirodela polyrrhiza and Lemna minor . ) . The volume of each channel was 225 m 3 , an average surface area of 322 m 2 , L/W ratio= 13.1 and depth of 0.7 m. The wastewater flow was 19.7 m 3 d -1 , for each system and the theoretical hydraulic retention time was 11.5 days. The ponds were monitored for the following parameters: Organic matter (BOD 5 ), total suspended solids (TSS), ammonium nitrogen (NH 4+ -N), total Kjeldahl nitrogen (TKN), nitrite nitrogen (NO 2 -N), nitrate nitrogen (NO 3 -N), total phosphorous (TP) and faecal coliform (FC). The duckweed pond developed different environmental conditions in terms of pH, temperature and oxygen, compared to the algae pond. The duckweed pond was more efficient in removing organic matter and the algae pond was more efficient in nitrogen removal. Denitrification accounted for most of the nitrogen removal in the algae and duckweed ponds. The second most important mechanism for nitrogen removal was ammonia volatilization for the algae pond and plant up-take for the duckweed pond. In the design of duckweed pond systems special attention should be paid to the reactor configuration and flow pattern in order to obtain good contact between water column and the duckweed cover and to reduce hydraulic problems.

    Practical applications.

    Wastewater treatment can be converted into an attractive, feasible and sustainable alternative by combining anaerobic pretreatment, duckweed ponds, and algae ponds. The integrated system UASB reactor, algae pond and duckweed pond offers the possibility to remove the various unwanted component in wastewater and to recover part of the valuable material present in the wastewater in the form of biomass or biogas The effluents may be suitable for discharge or for irrigation depending on the removal efficiencies of the system. The design and operation of this integrated system may have two different approaches. Firstly, one could optimize nitrogen recovery by duckweed uptake and effluent irrigation. Secondly, one could maximize nitrogen removal in order to protect the receiving water resources. 

    If the objective of the treatment is recovery of nitrogen then the stimulation of duckweed incorporation and the reduction of effluent nitrogen to a suitable range for irrigation would be the best option. The configuration of an efficient anaerobic pre-treatment followed by a series of ponds completely covered with duckweed would be recommendable. Influent ammonium nitrogen concentration below 50 mg l -1 and pH below 8 would be desirable to avoid biomass growth inhibition. The comparison between two pond systems with different depths and the same hydraulic surface loading rate showed similar nitrogen removals in the shallower system as in the deeper system. This means that duckweed pond system could be designed with the shallower depth without affecting nitrogen removal efficiency. Shallow ponds are easier to build, to operate and to maintain and in the case of duckweed covered ponds, they can be regarded as a crop production system.

    If the objective of the treatment is nitrogen removal due to disposal regulations, a strategy to enhance denitrification should be adopted. Higher nitrogen removals may be obtained in duckweed pond systems through the introduction of aerobic zones in early stages of the system, which allows a considerable reduction of the hydraulic retention time. Strict nitrogen effluent criteria can therefore be met at relatively short hydraulic retention times. The configuration of the system, in particular the down and up flow pattern seems to have an important positive effect on denitrification rates. Compartmentalization of the treatment system improves the pond performance. In the design of pond systems special attention should be paid to the reactor configuration and hydraulic flow pattern, good contact water-biomass and to avoidance of short circuiting and dead zones. In the process of technology development the following studies are envisaged and recommended for further research: Future studies should be focused on shallow ponds with the views to enhance nitrogen removal via its recovery in the form of duckweed biomass. Shallow ponds will also reduce construction cost of the treatment systems.

    Alternative uses of treated effluent and produced biomass should be investigated.In the case of effluent reuse on irrigation, the reduction of nitrogen concentrations in the treatment system to 15-25 mg l -1 will be enough. The use of vegetable biomass as a food complement on the diet of fish and pork is an alternative that has been preliminary explored in the area of research. Further studies are necessary to determine its feasibility.For safe discharge of effluent to open water bodies, effluent nitrogen concentration should be low. In this case nitrogen removal processes may be influence by affecting growth conditions of nitrifiers/dentrifiers like oxygen levels or availability of area for bacterial attachment. It is important to performed studies in order to find the best combination of duckweed and algae ponds for nitrogen removal. The introduction of baffles on the treatment channels will increase the availability of area for biomass growth and will improved the hydraulic characteristics of the treatment systems. The appropriated number and distribution of baffles should be investigated. Recycling of final aerobic effluent to the UASB reactor or to the entrance of the duckweed pond could be an interesting option to stimulate denitrification. Pathogen removal will be affected by the use of low pond depths, the presence of aerobic zones and compartmentalization in the treatment system. These effects should be researched in order to optimizedalso the removal of pathogenic microorganisms.
    Performance of UASB septic tank for treatment of concentrated black water within DESAR concept
    Kujawa-Roeleveld, K. ; Fernandes, T. ; Wiryawan, Y. ; Tafwik, A. ; Visser, M. de; Zeeman, G. - \ 2005
    Water Science and Technology 52 (2005)1-2. - ISSN 0273-1223 - p. 307 - 313.
    afvalwater - scheiding - anaërobe behandeling - hergebruik van water - afvalwaterbehandeling - verzamelen - waste water - separation - anaerobic treatment - water reuse - waste water treatment - collection - waste-water
    Separation of wastewater streams produced in households according to their origin, degree of pollution and affinity to a specific treatment constitutes a starting point in the DESAR concept (decentralised sanitation and reuse). Concentrated black water and kitchen waste carry the highest load of organic matter and nutrients from all waste(water)streams generated from different human activities. Anaerobic digestion of concentrated black water is a core technology in the DESAR concept. The applicability of the UASB septic tank for treatment of concentrated black water was investigated under two different temperatures, 15 and 25 °C. The removal of total COD was dependent on the operational temperature and attained 61 and 74% respectively. A high removal of the suspended COD of 88 and 94% respectively was measured. Effluent nutrients were mainly in the soluble form. Precipitation of phosphate was observed. Effective sludge/water separation, long HRT and higher operational temperature contributed to a reduction of E. coli. Based on standards there is little risk of contamination with heavy metals when treated effluent is to be applied in agriculture as fertiliser.
    Trace metal dynamics in methanol fed anaerobic granular sludge bed reactors
    Zandvoort, M.H. - \ 2005
    Wageningen University. Promotor(en): Gatze Lettinga, co-promotor(en): Piet Lens. - Wageningen : - ISBN 9789085041467 - 208
    anaërobe behandeling - rioolslib - metalen - sporenelementen - milieuafbraak - anaerobic treatment - sewage sludge - metals - trace elements - environmental degradation
    Trace metals are essential for anaerobic microorganisms, because they are present as cofactor in many of their enzymes. Therefore anaerobic wastewater treatment systems using these microorganisms to perform biological conversions are dependent on these metals for their (optimal) performance. In practice these metals are supplied to the influent when they are absent or insufficiently present in the wastewater. This supply is generally not very rational. However, such a rational metal supply is desired in order to reduce the costs, to minimize the introduction into the environment and to maximize the biological activity. To achieve this insight, in the trace metal dynamics in anaerobic granular sludge bed reactors is required. This thesis therefore focuses on the retention, accumulation and release of trace metals in anaerobic granular sludge and the factors affecting these processes. Further the impact of metal presence/absence and dosing on the anaerobic conversion of methanol was addressed
    Effect of inoculum and sludge concentration of viscosity evolution of anaerobic granular sludges
    Pevere, A. ; Guibaud, G. ; Hullebusch, E.D. van; Lens, P.N.L. ; Baudu, M. - \ 2005
    Water Science and Technology 52 (2005)1-2. - ISSN 0273-1223 - p. 509 - 514.
    slib - anaërobe behandeling - reologische eigenschappen - spijsvertering - viscositeit - afvalwaterbehandeling - korrels - sludges - anaerobic treatment - rheological properties - digestion - viscosity - waste water treatment - granules - rheological characterization - sewage sludges - reactors - sorption - nickel - cobalt - uasb
    The rheological behaviour of granular sludges (diameter 20-315 ¿m) originating from different anaerobic reactors was carried out using rotation tests. The sieved granular sludges suspensions display a non-Newtonian rheological behaviour and the limit viscosity was therefore used as a rheological parameter. The values obtained, which depend on the shear rate used, were strongly influenced by the total suspended solids (TSS) content of granular sludge and an exponential relation was found between the TSS and the rheological parameter limit viscosity. The increase of viscosity as a function of TSS content of the granular sludge as well as the increase of granule size underlines the importance of the interaction between granules in the evolution of this rheological parameter. Significant differences in granular sludge limit viscosity were found for granular sludge of different origins. All measurements performed with 10 g·l-1 TSS granular sludge indicate the ability of the chosen rheological parameter to describe different granular sludge quality.
    Reductive decolourisation of azo dyes by mesophilic and thermophilic methanogenic consortia
    Cervantes, F.J. ; Santos, A.B. dos; Madrid, M.P. de; Stams, A.J.M. ; Lier, J.B. van - \ 2005
    Water Science and Technology 52 (2005)1-2. - ISSN 0273-1223 - p. 351 - 356.
    slib - ontkleuring - azoverbindingen - kleurstoffen (dyes) - anaërobe behandeling - redoxreacties - microbiële afbraak - afvalwaterbehandeling - sludges - decolorization - azo compounds - dyes - anaerobic treatment - redox reactions - microbial degradation - waste water treatment - anaerobic sludge - redox mediators - quinone-respiration - anthraquinone dyes - granular sludge - transformation - toxicity - bioreactors - inhibition - reactor
    The contribution of acidogenic bacteria and methanogenic archaea on the reductive decolourisation of azo dyes was assessed in anaerobic granular sludge. Acidogenic bacteria appeared to play an important role in the decolourising processes when glucose was provided as an electron donor; whereas methanogenic archaea showed a minor role when this substrate was supplemented in excess. In the presence of the methanogenic substrates acetate, methanol, hydrogen and formate, methane production became important only after colour was totally removed from the batch assays. This retardation in methane production may be due to either a toxic effect imposed by the azo dyes or to the competitive behaviour of azo dyes to the methanogenic consortia for the available reducing equivalents. Keywords Azo dyes; decolourisation; methanogenic consortium; redox mediator; inhibitors
    Reductive Decouloristation of Dyes by Thermophilic Anaerobic Granular Sludge
    Bezerra Dos Santos, A. - \ 2005
    Wageningen University. Promotor(en): Cees Buisman, co-promotor(en): Jules van Lier; F.J. Cervantes. - [S.l.] : S.n. - ISBN 9789085041344 - 176
    ontkleuring - kleurstoffen (dyes) - azoverbindingen - textielindustrie - bioreactoren - afvalwaterbehandeling - anaërobe behandeling - decolorization - dyes - azo compounds - textile industry - bioreactors - waste water treatment - anaerobic treatment
    The colour removal achieved under anaerobic conditions is also called reductive decolourisation, which is composed of a biological part, i.e. the reducing equivalents are biologically generated, and a chemical part, i.e. the formed electrons reduce chemically the dyes. The overall objective of this research was to explore different strategies to increase the reduction of dyes in bioreactors by using thermophilic anaerobic granular sludge and redox mediators
    Thermophilic (55 - 65°C) and extreme thermophilic (70 - 80°C) sulfate reduction in methanol and formate-fed UASB reactors
    Vallero, M.V.G. ; Camarero, E. ; Lettinga, G. ; Lens, P.N.L. - \ 2004
    Biotechnology Progress 20 (2004)5. - ISSN 8756-7938 - p. 1382 - 1392.
    anaërobe behandeling - afvalwaterbehandeling - methanol - reductie - sulfaten - temperatuur - anaerobic treatment - waste water treatment - methanol - reduction - sulfates - temperature - rate anaerobic reactor - volatile fatty-acids - 55-degrees-c - sludge - degradation - conversion - bacterium - methanogenesis - competition - performance
    The feasibility of thermophilic (55-65 degreesC) and extreme thermophilic (70-80 degreesC) sulfate-reducing processes was investigated in three lab-scale upflow anaerobic sludge bed (UASB) reactors fed with either methanol or formate as the sole substrates and inoculated with mesophilic granular sludge previously not exposed to high temperatures
    The feasibility of thermophilic (55-65 degreesC) and extreme thermophilic (70-80 degreesC) sulfate-reducing processes was investigated in three lab-scale upflow anaerobic sludge bed (UASB) reactors fed with either methanol or formate as the sole substrates and inoculated with mesophilic granular sludge previously not exposed to high temperatures. Full methanol and formate degradation at temperatures up to, respectively, 70 and 75 degreesC, were achieved when operating UASB reactors fed with sulfate rich (COD/SO42- = 0.5) synthetic wastewater. Methane-producing archaea (MPA) outcompeted sulfate-reducing bacteria (SRB) in the formate-fed UASB reactor at all temperatures tested (65-75 degreesC). In contrast, SRB outcompeted MPA in methanol-fed UASB reactors at temperatures equal to or exceeding 65 degreesC, whereas strong competition between SRB and MPA was observed in these reactors at 55 degreesC. A short-term (5 days) temperature increase from 55 to 65 degreesC was an effective strategy to suppress methanogenesis in methanol-fed sulfidogenic UASB reactors operated at 55 degreesC. Methanol was found to be a suitable electron donor for sulfate-reducing processes at a maximal temperature of 70 degreesC, with sulfide as the sole mineralization product of methanol degradation at that temperature.
    Robustness of UASB Reactors Treating Sewage Under Tropical Conditions
    Leitao, R. - \ 2004
    Wageningen University. Promotor(en): Gatze Lettinga, co-promotor(en): Grietje Zeeman; A.C. van Haandel. - [S.l.] : S.n. - ISBN 9789085040453 - 160
    anaërobe omstandigheden - rioolslib - afvalwaterbehandeling - retentie - dysregulatie - hydraulische apparatuur - tropisch klimaat - anaërobe behandeling - anaerobic conditions - sewage sludge - waste water treatment - retention - dysregulation - hydraulic equipment - tropical climate - anaerobic treatment
    This PhD thesis presents results and discussions to elucidate the matters of performance and robustness of the Upflow Anaerobic Sludge Blanket (UASB) reactors for the treatment of municipal wastewater in tropical countries. The research focuses on the main operational parameters (hydraulic retention time -HRT, influent COD concentration - COD Inf , organic loading rate - OLR, and sludge retention time - SRT) that affect the UASB loading potentials and its performance in "steady state" conditions, and on the response of the system when submitted to transient conditions.

    The experimental investigation was performed using 11 pilot-scale UASB reactors (120 L) which were organised into three sets: Set 1, five reactors were operated with the same hydraulic retention time (HRT = 6 h) and different COD Inf , ranging from 92 to 816 mg/L. Set 2, four reactors were operated with approximately the same COD Inf (~800 mg/L), but with different HRTs, ranging from 1 to 6 hours. Set 3, the HRTs were identical to the second phase but the COD Inf was adapted to have approximately the same OLR in the four reactors (~3.3 kgCOD/m 3 .day).

    In the first experimental part of the research, data was collected in order to evaluate the "steady state" performance and robustness of UASB reactors on the basis of COD removal efficiency, effluent variability, and pH stability. After the "steady state" condition was achieved, the sludge of each reactor was tested in terms of Specific Methanogenic Activity (SMA), biodegradability, settleability and, expansibility. In the second part of the experimental research, the robustness and stability of the system were evaluated under hydraulic and organic shock loads. Four indicators were defined for that purpose: COD removal efficiency, effluent variability, pH stability, and recovery time.

    Under "steady state" conditions, UASB reactors can treat sewage with COD as low as 200 mg/L, and HRT as low as 2 h, but the maximum efficiency is achieved with an HRT longer than 4h, and COD Inf higher than 300 mg/L. Effluent variability is highly dependent on the influent variability, showing that the reactors do not attenuate the daily fluctuation of the COD Inf . UASB reactors treating sewage in tropical countries are extremely stable with regards to pH and buffer capacity. With regards to the biological properties of the sludge, the reactors operated with a short HRT produce sludge with a high SMA. Moreover, sludge of reactors operated with a long HRT and with a low COD Inf resulted in low biodegradability. With respect to the hydrodynamic characteristics of the sludge, reactors operated with a high COD Inf and/or a short HRT produced sludges with high settleability and low expansibility. Results show that it is useless to design a UASB reactor with a longer HRT to cope with organic or hydraulic shock loads.

    Under shock load conditions the reactors resulted in COD removal efficiencies in the same range as during "steady state" conditions. The effluent COD fluctuates in the same range of the COD Inf variation, showing that the reactors are unable to attenuate strong variation in the OLR. The recovery time from a shock load is always very short, as the reactors needed less than 18 hours after the shock ceased to resume performance. The reactors showed signals that they would acidify if the organic shock load continued. However, hydraulic shock loads barely affected the pH stability of the reactors.

    Finally, the results obtained during this study showed that this kind of reactor is very robust with regards to the COD removal efficiency, as it keeps its maximum performance, in either "steady state" or transient conditions. Regarding to the pH stability, the UASB reactors also demonstrated extraordinary robustness, even when they are operated under extreme operational situations, which rarely occur in municipal wastewater treatment plants. When a shock load is imposed they need a very short time to recover. However, the UASB reactors are not robust with regard to effluent variability. Regarding this matter, the robustness of the reactors can be improved with the implementation of a secondary settler.

    Anaerobic sludge granulation
    Hulshoff Pol, L.W. ; Castro Lopes, S.I. de; Lettinga, G. ; Lens, P.N.L. - \ 2004
    Water Research 38 (2004)6. - ISSN 0043-1354 - p. 1376 - 1389.
    rioolslib - anaërobe behandeling - korrels - afvalwaterbehandeling - sewage sludge - anaerobic treatment - granules - waste water treatment - uasb reactors - start-up - molecular-mechanism - blanket reactors - bed reactors - hydrophobicity - pelletization - architecture - performance
    This paper reviews different theories on anaerobic sludge granulation in UASB-reactors that have been proposed during the past two decades
    This paper reviews different theories on anaerobic sludge granulation in UASB-reactors that have been proposed during the past two decades. The initial stages of the formation of anaerobic granules follow the same principles as biofilm formation of bacteria on solid surfaces. There exist strong evidence that inert carriers play an important positive role in granulation. Most researchers conclude that Methanosaeta concilii is a key organism in granulation. Only the Cape Town Hypothesis presumes that an autotrophic hydrogenotrophic organism, i.e., Methanobacterium strain AZ, growing under conditions of high H-2-pressures, is the key organism in granulation. Many authors focus on the initial stage of granulation, and only a few contributions discuss the latter stages in granulation: granule maturation and multiplication. Granule enhancing factors in the latter stages predominantly rely on manipulation of the selection pressure, through which selectively heavier sludge particles are retained in the UASB reactor. (C) 2003 Elsevier Ltd. All rights reserved.
    Nickel and cobalt sorption on anaerobic granular sludges: kinetic and equilibrium studies
    Hullebusch, E.D. van; Zandvoort, M.H. ; Lens, P.N.L. - \ 2004
    Journal of Chemical Technology and Biotechnology 79 (2004)11. - ISSN 0268-2575 - p. 1219 - 1227.
    slib - nikkel - kobalt - sorptie - kinetica - anaërobe behandeling - afvalwaterbehandeling - sludges - nickel - cobalt - sorption - kinetics - anaerobic treatment - waste water treatment - pseudomonas-fluorescens 4f39 - sphagnum moss peat - heavy-metals - aqueous-solution - waste-water - extracellular polymers - methanol degradation - removal - biosorption - ions
    The kinetics and equilibria of sorption of the divalent metal ions cobalt and nickel onto anaerobic granular sludge are described. Single component and binary equimolar systems were studied at different pH values (pH 6, 7 and 8). The kinetic modelling of metal sorption by anaerobic granular sludge has been carried out using Lagergren equations
    The kinetics and equilibria of sorption of the divalent metal ions cobalt and nickel onto anaerobic granular sludge are described. Single component and binary equimolar systems were studied at different pH values (pH 6, 7 and 8). The kinetic modelling of metal sorption by anaerobic granular sludge has been carried out using Lagergren equations. On fitting the experimental kinetic data both in first and pseudo-second-order equations, the regression analysis of a pseudo-second-order equation gave a higher r(2) value, indicating that both external mass transfer and intra-particle diffusion are involved in the sorption process. The experimental isotherm data were analysed using the Langmuir, Freundlich and Redlich-Peterson equations. The Redlich isotherm, a combination of the Langmuir and Freundlich equations, was found to have the highest regression correlation coefficients at pH 7. At pH 8, the Langmuir mechanism dominated for cobalt and nickel adsorption. In contrast, at pH 6, the Freundlich equation gave a better correlation coefficient which suggests a more heterogeneous adsorption at that pH. The maximal adsorption capacity of the granular sludge, as determined by the Langmuir equation, for cobalt or nickel in single systems (8.92 mg g(-1) Co TSS; 9.41 mg g(-1) Ni TSS, pH 7) compared with binary systems (8.06 mg g(-1) Co TSS; 8.43 mg g(-1) Ni TSS, pH 7) showed no great difference in the accumulation of these metals onto granular sludge. (C) 2004 Society of Chemical Industry.
    Effect of different redox mediators during thermophilic azo dye reduction by anaerobic granular sludge and comparative study between mesophilic (30C) and thermophilic (55C) treatments for decolourisation of textile wastewaters
    Bezerra Dos Santos, A. ; Bisschops, I.A.E. ; Cervantes, F.J. ; Lier, J.B. van - \ 2004
    Chemosphere 55 (2004)9. - ISSN 0045-6535 - p. 1149 - 1157.
    afvalwater - degradatie - consortia - toxiciteit - waterverontreiniging - ontkleuring - anaërobe behandeling - afvalwaterbehandeling - redoxreacties - azoverbindingen - kleurstoffen (dyes) - slib - waste water - degradation - consortia - toxicity - water pollution - decolorization - anaerobic treatment - waste water treatment - redox reactions - azo compounds - dyes - sludges - waste-water - reactor - carbon - bn6
    The impact of different redox mediators on colour removal of azo dye model compounds and textile wastewater by thermophilic anaerobic granular sludge (55 C) was investigated in batch assays. Additionally, a comparative study between mesophilic (30 C) and thermophilic (55 C) colour removal was performed with textile wastewater, either in the presence or absence of a redox mediator
    The impact of different redox mediators on colour removal of azo dye model compounds and textile wastewater by thermophilic anaerobic granular sludge (55 degreesC was investigated in batch assays. Additionally, a comparative study between mesophilic (30 degreesC and thermophilic (55 degreesC colour removal was performed with textile wastewater, either in the presence or absence of a redox mediator. The present work clearly evidences the advantage of colour removal at 55 degreesC compared with 30 degreesC when dealing with azo coloured wastewaters. The impact of the redox mediators anthraquinone-2,6-disulfonate (AQDS), anthraquinone-2-sulfonate (AQS) and riboflavin was evident with all dyes, increasing decolourisation rates up to 8-fold compared with the mediator-free incubations. The generation of the hydroquinone form AH(2)QDS, i.e. the reduced form of AQDS, was extremely accelerated at 55 degreesC compared with 30 degreesC. Furthermore, no lag-phase was observed at 55 degreesC. Based on the present results we postulate that the production/transfer of reducing equivalents was the process rate-limiting step, which was accelerated by the temperature increase. It is conclusively stated that 55 degreesC is a more effective temperature for azo dye reduction than 30 degreesC which on the one hand can be attributed to the faster production/transfer of reducing equivalents, but also to the decrease in activation energy requirements. (C) 2004 Elsevier Ltd. All rights reserved.
    Effect of carbon monoxide, hydrogen and sulfate on thermophilic (55°C) hydrogenogenic carbon monoxide conversion in two anaerobic bioreactor sludges
    Sipma, J. ; Meulepas, R.J.W. ; Stams, A.J.M. ; Lettinga, G. ; Lens, P.N.L. - \ 2004
    Applied Microbiology and Biotechnology 64 (2004)3. - ISSN 0175-7598 - p. 421 - 428.
    slib - anaërobe behandeling - koolmonoxide - afvalwaterbehandeling - bioreactoren - sludges - anaerobic treatment - carbon monoxide - waste water treatment - bioreactors - methanogenic bacteria - synthesis-gas - energy - reduction - growth - metabolism - oxidation - reactor - co2
    The conversion routes of carbon monoxide (CO) at 55°C by full-scale grown anaerobic sludges treating paper mill and distillery wastewater were elucidated. Inhibition experiments with 2-bromoethanesulfonate (BES) and vancomycin showed that CO conversion was performed by a hydrogenogenic population and that its products, i.e. hydrogen and CO2, were subsequently used by methanogens, homo-acetogens or sulfate reducers depending on the sludge source and inhibitors supplied. Direct methanogenic CO conversion occurred only at low CO concentrations [partial pressure of CO (P CO) 1.6 bar), indicating that CO-rich synthesis gas
    The conversion routes of carbon monoxide (CO) at 55degreesC by full-scale grown anaerobic sludges treating paper mill and distillery wastewater were elucidated. Inhibition experiments with 2-bromoethanesulfonate (BES) and vancomycin showed that CO conversion was performed by a hydrogenogenic population and that its products, i.e. hydrogen and CO2, were subsequently used by methanogens, homo-acetogens or sulfate reducers depending on the sludge source and inhibitors supplied. Direct methanogenic CO conversion occurred only at low CO concentrations [partial pressure of CO (P-CO) 1.6 bar), indicating that CO-rich synthesis gas can be used efficiently as an electron donor for biological sulfate reduction.
    Anaerobic stabilisation and conversion of biopolymers in primary sludge-effect of temperature and sludge retention time
    Mahmoud, N. ; Zeeman, G. ; Gijzen, H.J. ; Lettinga, G. - \ 2004
    Water Research 38 (2004)4. - ISSN 0043-1354 - p. 983 - 991.
    anaërobe behandeling - rioolslib - afvalwaterbehandeling - anaërobe afbraak - biodegradatie - anaerobic treatment - sewage sludge - waste water treatment - anaerobic digestion - biodegradation - domestic sewage - digestion - hydrolysis - lipids - water - acid
    The effect of sludge retention time (SRT) and process temperature on the hydrolysis, acidification and methanogenesis of primary sludge was investigated in completely stirred tank reactors (CSTRs). The CSTRs were operated to maintain SRTs of 10, 15, 20 and 30 days at process temperatures of 25°C and 35°C. The rates of hydrolysis and the biodegradability of primary sludge were assessed in batch reactors incubated at 15°C, 25°C and 35°C
    The effect of sludge retention time (SRT) and process temperature on the hydrolysis, acidification and methanogenesis of primary sludge was investigated in completely stirred tank reactors (CSTRs). The CSTRs were operated to maintain SRTs of 10, 15, 20 and 30 days at process temperatures of 25degreesC and 35degreesC. The rates of hydrolysis and the biodegradability of primary sludge were assessed in batch reactors incubated at 15degreesC, 25degreesC and 35degreesC. The results revealed that the major amount of sludge stabilisation occurred between 0 and 10 days at 35degreesC and 10 and 15 days at 25degreesC. Hydrolysis was found to be the rate limiting-step of the overall digestion process, for the reactors operated at 35degreesC and 25degreesC, except for the reactor operated at 10 days and 25degreesC. At the latter conditions, methanogenesis was the rate-limiting step of the overall digestion process. Proteins hydrolysis was limited to a maximum value of 39% at 30 days and 35degreesC due to proteins availability in the form of biomass. The biodegradability of primary sludge was around 60%, and showed no temperature dependency. The hydrolysis of the main biopolymers and overall particulate COD of the primary sludge digested in CSTRs were well described by first-order kinetics, in case hydrolysis was the rate-limiting step. Similarly, the hydrolysis of the overall particulate COD of the primary sludge digested in batch reactors were described by first-order kinetics and revealed strong temperature dependency, which follows Arrhenius equation. (C) 2003 Elsevier Ltd. All rights reserved.
    Heavy metals removal from anaerobically digested sludge
    Marchioretto, M.M. - \ 2003
    Wageningen University. Promotor(en): Wim Rulkens, co-promotor(en): Harry Bruning. - [S.l.] : S.n. - ISBN 9789058089083 - 142
    zware metalen - rioolslib - anaërobe behandeling - sulfaat reducerende bacteriën - bioreactoren - heavy metals - sewage sludge - anaerobic treatment - sulfate reducing bacteria - bioreactors
    Sulfate reducing processes at extreme salinity and temperature. extending its application window
    Vallero, M.V.G. - \ 2003
    Wageningen University. Promotor(en): Gatze Lettinga, co-promotor(en): Piet Lens. - [S.l.] : S.n. - ISBN 9789058089090 - 214
    sulfaat reducerende bacteriën - zoutgehalte - anaërobe behandeling - bioreactoren - membranen - sulfate reducing bacteria - salinity - anaerobic treatment - bioreactors - membranes
    The characteristics of various sulfate-rich wastewaters, such as temperature, pH and salinity, are determined by the (industrial) process from which they originate, and can be far from the physiological optima of the sulfur cycle microorganisms. The main goal of the research described in this thesis was to investigate and develop high rate sulfate reducing wastewater treatment processes for the treatment of inorganic sulfate-rich wastewaters under extreme conditions, i.e. high temperature and high salinity. In this thesis, several simple organic bulk chemicals were tested as electron donor, viz. lower alcohols (methanol and ethanol) and volatile fatty acids (formate, acetate and propionate).

    With respect to the start-up of anaerobic sludge bed (UASB) reactors at high salinity or high temperature, the results obtained in this investigation indicate that the appearance of a targeted metabolic property (sulfate reduction at high salinity or at high temperature) is independent of the strategy for biomass acclimation (direct exposure vs. stepwise exposure).The stepwise adaptation of thermophilicsulfidogenic methanol degrading biomass to a highosmolarity environment, both at 55C or at 70C, likely does not occur in UASB reactors, as probably no methanol halotolerant thermophilic sulfate reducing bacteria (SRB) were present in the thermophilicinoculumsludge used in the investigations described in this thesis. Exposing the sludge directly to a very high salinity (50 g NaCl.L -1 ) stimulated the growth of amesophilic(30C) propionate- and ethanol-utilizinghalotolerantSRB population, which supported high rate sulfate reduction (up to 3.6 g SO 42- .L -1 .day -1 ) in a UASB reactor. The start-up ofthermophilic(55 to 65C) and extremethermophilicC or higher) anaerobic bioreactors inoculated withmesophilicsludgesat the targeted temperature proceeded fast and stable, as it provoked the rapid selection of (extreme)thermophiles. Therefore, the key for the successful treatment of high salinity or hot wastewaters is to invest enough time for the growth of the targeted microorganism in the biomass.

    The results of this investigation show that the competition between SRB, methane producingarchaeaandacetogenicbacteria for substrate is highly dependent of the type of substrate and operational conditions imposed to the bioreactor. This thesis describes a situation where the production of acetate and methane was completely suppressed in methanol-fed sulfate reducing UASB reactors operated at 70C. As a result, for the first time a fully sulfate reducing granular sludge has been cultivated in a methanol-fedthermophilicsulfate reducing reactor (with sulfate reduction rates as high as 14.4 g SO 42- .L -1 .day -1 ), provided that an operational temperature of 70C is kept. The production of methane can be easily suppressed inthermophilicmethanol fed reactors, either by running the reactor at temperatures equal or higher than 65C or by exposing 55C operated reactors to a short (2 days) temperature (65 - 70C) shock.Methanogenesiscan also be easily suppressed inmesophilicpropionate- and ethanol-fed reactors, provided high salinity conditions prevail (e.g. above 50 mS.cm -1 ). It seems, however, that the production of acetate, with the exception of methanol-fed reactors operated at 70C, is unavoidable both inthermophilicandmesophilicreactors.

    This thesis also describes the use of specialized microorganisms, the halophilicDesulfobacterhalotolerans , in bioreactors for the treatment of saline sulfate-rich wastewaters. Very high specific sulfate reduction rates (up to 6.6 g SO 42- .gVSS -1 .day -1 ) can be obtained in completely mixed tank reactors where the biomass grows in suspension and can be efficiently retained by membranes which are submerged in the reactor system. This investigation showed that anaerobic membrane bioreactors can be operated over extended periods of time at a fixed flux, if this flux is substantially below the nominal critical flux determined experimentally (18-21 L.m -2 .h -1 ). Chemical cleaning of the membranes will be required only at about 106 days, as long a low constant flux is imposed (4.7 L.m -2 .h .1 ) and intermittentbackflush(e.g. 1 minute each 10 minutes) is adopted as operational strategy.
    Development of a novel Process for the Biological conversion of H2S and Methanethiol to Elemental Sulfur
    Sipma, J. ; Janssen, A.J.H. ; Hulshoff Pol, L.W. ; Lettinga, G. - \ 2003
    Biotechnology and Bioengineering 82 (2003)1. - ISSN 0006-3592 - p. 1 - 11.
    afvalwaterbehandeling - anaërobe behandeling - zwavel - rioolafvalwater - slib - methanol - reductie - bioreactoren - waste water treatment - anaerobic treatment - sulfur - sewage effluent - sludges - methanol - reduction - bioreactors - granular sludge reactor - methylotrophic methanogen - sp-nov - waste-water - estuarine methanogen - sulfide - degradation - sediments - dimethylsulfide - bacterium
    The feasibility of anaerobic treatment of wastewater containing methanethiol (MT), an extremely volatile and malodorous sulfur compound, was investigated in lab-scale bioreactors. Inoculum biomass originating from full-scale anaerobic wastewater treatment facilities was used. Several sludges were tested for their ability to degrade MT
    The feasibility of anaerobic treatment of wastewater containing methanethiol (MT), an extremely volatile and malodorous sulfur compound, was investigated in lab-scale bioreactors. Inoculum biomass originating from full-scale anaerobic wastewater treatment facilities was used. Several sludges, tested for their ability to degrade MT, revealed the presence of organisms capable of metabolizing MT as their sole source of energy. Furthermore, batch tests were executed to gain a better understanding of the inhibition potential of MT. It was found that increasing MT concentrations affected acetotrophic organisms more dramatically than methylotrophic organisms. Continuous reactor experiments, using two lab-scale upflow anaerobic sludge bed (UASB) reactors (R1 and R2), aimed to determine the maximal MT load and the effect of elevated sulfide concentrations on MT conversion. Both reactors were operated at a hydraulic retention time (HRT) of about 7 hours, a temperature of 30degreesC, and a pH of between 7.3 and 7.6. At the highest influent MT concentration applied, 14 mM in R1, corresponding to a volumetric loading rate of about 50 mM MT per day, 87% of the organic sulfur was recovered as hydrogen sulfide (12.2 mM) and the remainder as volatile organic sulfur compounds (VOSCs). Upon decreasing the HRT to 3.5 to 4.0 h at a constant MT loading rate, the sulfide concentration in the reactor decreased to 8 mM and MT conversion efficiency increased to values near 100%. MT conversion was apparently inhibited by the high sulfide concentrations in the reactor. The specific MT degradation rate, as determined after 120 days of operation in R1, was 2.83 +/- 0.27 mmol MT g VSS-1 day(-1). During biological desulfurization of liquid hydrocarbon phases, such as with liquefied petroleum gas (LPG), the combined removal of hydrogen sulfide and MT is desired. In R2, the simultaneous addition of sodium sulfide and MT was therefore studied and the effect of elevated sulfide concentrations was investigated. The addition of sodium sulfide resulted in enhanced disintegration of sludge granules, causing significant washout of biomass. Additional acetate, added to stimulate growth of methanogenic bacteria to promote granulation, was hardly converted at the termination of the experimental period. (C) 2003 Wiley Periodicals, Inc.
    Effect of specific gas loading rate on thermophilic (55°) acidifying (pH6) and sulfate reducing granular sludge reactors
    Lens, P.N.L. ; Klijn, R. ; Lier, J.B. van; Lettinga, G. - \ 2003
    Water Research 37 (2003). - ISSN 0043-1354 - p. 1033 - 1047.
    afvalwaterbehandeling - anaërobe behandeling - temperatuur - verzuring - sulfaten - reductie - anaërobe afbraak - waste water treatment - anaerobic treatment - temperature - acidification - sulfates - reduction - anaerobic digestion - fatty-acid degradation - waste-water treatment - anaerobic-digestion - blanket reactors - uasb reactors - system - methanogenesis - velocity - sulfide
    The effect of the specific gas loading rate on the acidifying, sulfate reducing and sulfur removal capacity of thermophilic (55degreesC; pH 6.0) granular sludge bed reactors treating partly acidified wastewater was investigated. A comparison was made between a regular UASB reactor and a UASB reactor continuously sparged with N-2 at a specific gas loading rate of 30 m(3) m(-2) d(-1). Both UASB reactors (upflow velocity 1.0 m h(-1), hydraulic retention time about 5 h) were fed a synthetic wastewater containing starch, sucrose, lactate, propionate and acetate and a low sulfate concentration (COD/SO42- ratio of 10) at volumetric organic loading rates (OLR) ranging from 4.0 to 49.8 gCOD l(-1) reactor d(-1). Immediately after imposing an OLR of 25 gCOD l(-1) reactor d(-1), the acidification and sulfate reduction efficiency dropped to 80% and 30%, respectively, in the UASB reactor. Both efficiencies recovered slowly to 100% during the course of the experiment. In the N-2 SParged reactor, both the acidification and sulfate reduction efficiency remained 100% following the OLR increase to 25 gCOD l(-1) reactor d(-1). However, the sulfate reduction efficiency gradually decreased to about 20% at the end of the experiment. The biogas (CO2 and CH4) production rate in the UASB was very low,-i.e.
    Effect of NaCl on thermophilic (55°C) methanol degradation in sulfate reducing granular sludge reactors
    Vallero, M.V.G. ; Hulshoff Pol, L.W. ; Lettinga, G. ; Lens, P.N.L. - \ 2003
    Water Research 37 (2003)10. - ISSN 0043-1354 - p. 2269 - 2280.
    anaërobe behandeling - afvalwaterbehandeling - methanol - reductie - natriumchloride - sulfaten - rioolafvalwater - slib - anaerobic treatment - waste water treatment - methanol - reduction - sodium chloride - sulfates - sewage effluent - sludges - sp-nov - processing wastewaters - sodium inhibition - bacteria - methanogenesis - temperature - antagonism - digestion
    The effect of NaCl on thermophilic (55degreesC) methanol conversion in the presence of excess of sulfate (COD/SO42-=0.5) was investigated in two 6.5L lab-scale upflow anaerobic sludge bed reactors inoculated with granular sludge previously not adapted to NaCl
    The effect of NaCl on thermophilic (55degreesC) methanol conversion in the presence of excess of sulfate (COD/SO42-=0.5) was investigated in two 6.5L lab-scale upflow anaerobic sludge bed reactors inoculated with granular sludge previously not adapted to NaCl. Methanol was almost completely used for sulfate reduction in the absence of NaCl when operating at an organic loading rate of 5 g COD L-1 day(-1) and a hydraulic retention time of 10 h. The almost fully sulfidogenic sludge consisted of both granules and flocs developed after approximately 100 days in both reactors. Sulfate reducing bacteria (SRB) outcompeted methane producing archaea (MPA) for methanol, but acetate represented a side-product, accounting for maximal 25% of the total COD converted. Either MPA or SRB did not use acetate as substrate in activity tests. High NaCl concentrations (25 g L-1) completely inhibited methanol degradation, whereas low salt concentrations (2.5 g NaCl L-1) provoked considerable changes in the metabolic fate of methanol. The MPA were most sensitive towards the NaCl shock (25 g L-1). In contrast, the addition of 2.5 g L-1 of NaCl stimulated MPA and homoacetogenic bacteria. (C) 2003 Elsevier Science Ltd. All rights reserved.
    Enrichment and immobilization of quinone-respiring bacteria in anaerobic granular sludge
    Cervantes-Carillo, F.J. ; Duong-Dac, T. ; Roest, K. de; Akkermans, A.D.L. ; Lettinga, G. ; Field, J.A. - \ 2003
    Water Science and Technology 48 (2003). - ISSN 0273-1223 - p. 9 - 16.
    anaërobe behandeling - immobilisatie - micro-organismen - slib - chinonen - afvalwaterbehandeling - korrels - reductie - anaerobic treatment - immobilization - microorganisms - sludges - quinones - waste water treatment - granules - reduction - electron-acceptors - humic substances - carbon-tetrachloride - microbial oxidation - redox mediators - dye reduction - azo dyes - respiration - recovery
    The capacity of an anaerobic granular sludge for serving as an immobilizing mechanism for quinone-respiring bacteria was evaluated. The inoculum was continuously fed with a basal medium containing the humic model compound, anthraquinone-2,6-disulfonate (AQDS), as a terminal electron acceptor. Complete reduction of AQDS was achieved by the granular sludge for a prolonged period in an anaerobic bioreactor provided with a mixture of volatile fatty acids as a substrate. Phylogenetic analysis revealed the enrichment and immobilization of AQDS-respiring bacteria appearing as dominant organisms in the microbial population of the AQDS-supplemented reactor, compared to a reactor control operated under methanogenic conditions
    The capacity of an anaerobic granular sludge for serving as an immobilizing mechanism for quinone-respiring bacteria was evaluated. The inoculum was continuously fed with a basal medium containing the humic model compound, anthraquinone-2,6-disulfonate (AQDS), as a terminal electron acceptor. Complete reduction of AQDS was achieved by the granular sludge for a prolonged period in an anaerobic bioreactor provided with a mixture of volatile fatty acids as a substrate. Phylogenetic analysis revealed the enrichment and immobilization of AQDS-respiring bacteria appearing as dominant organisms in the microbial population of the AQDS-supplemented reactor, compared to a reactor control operated under methanogenic conditions. The consistent quinone-reducing capacity observed in the consortium indicates that it is feasible to apply quinone-reducing microorganisms in continuous bioreactors and this ability can potentially be important in wastewaters rich in humic substances. The quinone reducing activity could also be applied to accelerate the conversion of xenobiotics susceptible to reductive biotransformations such as azo dyes and polychlorinated compounds in continuous bioreactors.
    Methane production by anaerobic digestion of wastewater and solid wastes
    Mes, T.Z.D. de; Stams, A.J.M. ; Reith, J.H. ; Zeeman, G. - \ 2003
    In: Bio-methane & Bio-hydrogen: status and perspectives of biological methane and hydrogen production Petten : Dutch Biological Hydrogen Foundation - ISBN 9789090171654 - p. 58 - 102.
    bio-energie - methaan - anaërobe afbraak - afvalwaterbehandeling - biogas - afvalverwerking - anaërobe behandeling - waterzuivering - energie - biobased economy - bioenergy - methane - anaerobic digestion - waste water treatment - biogas - waste treatment - anaerobic treatment - water treatment - energy - biobased economy
    Assessment of compatible solutes to overcome salinity stress in thermophilic (55 oC) methanol-fed sulfate reducing granular sludges
    Vallero, M.V.G. ; Lettinga, G. ; Lens, P.N.L. - \ 2003
    Water Science and Technology 48 (2003)6. - ISSN 0273-1223 - p. 195 - 202.
    anaërobe behandeling - afvalwaterbehandeling - methanol - reductie - natriumchloride - sulfaten - rioolafvalwater - slib - anaerobic treatment - waste water treatment - methanol - reduction - sodium chloride - sulfates - sewage effluent - sludges - glycine betaine - growing-cells - accumulation - degradation - adaptation - trehalose - glutamate - reactor
    High NaCl concentrations (25 g.L-1) considerably decreased the methanol depletion rates for sludges harvested from two lab-scale sulfate reducing UASB reactors. In addition, 25 gNaCl.L-1 strongly affected the fate of methanol degradation, with clear increase in the acetate production at the expense of sulfide and methane production. The addition of different osmoprotectants, viz. glutamate, betaine, ectoine, choline, a mixture of compatible solutes and K+ and Mg2+, slightly increased methanol depletion rates for UASB reactors sludges. However, the acceleration in the methanol uptake rate favored the homoacetogenic bacteria, as the methanol breakdown was steered to the formation of acetate without increasing sulfate reduction and methane production rates. Thus, the compatible solutes used in this work were not effective as osmoprotectants to alleviate the acute NaCl toxicity on sulfate reducing granular sludges developed in methanol degrading thermophilic (55°C) UASB reactors
    High NaCl concentrations (25 g(.)L(-1)) considerably decreased the methanol depletion rates for sludges harvested from two lab-scale sulfate reducing UASB reactors. In addition, 25 gNaCl.L-1 strongly affected the fate of methanol degradation, with clear increase in the acetate production at the expense of sulfide and,methane production. The addition of different osmoprotectants, viz. glutmate, betaine, ectoine, choline, a mixture of compatible solutes and K+ and Mg2+, slightly increased methanol depletion rates for UASB reactors sludges. However, the acceleration in the methanol uptake rate favored the homoacetogenic bacteria, as the methanol breakdown was steered to the formation of acetate without increasing sulfate reduction and methane production rates. Thus, the compatible solutes used in this work were not effective as osmoprotectants to alleviate the acute NaCl toxicity on sulfate reducing granular sludges developed in methanol degrading thermophilic (55degreesC) UASB reactors.
    Essential metal depletion in an anaerobic reactor
    Osuna, M.B. ; Iza, J.M. ; Zandvoort, M.H. ; Lens, P.N.L. - \ 2003
    Water Science and Technology 48 (2003)6. - ISSN 0273-1223 - p. 1 - 8.
    anaërobe behandeling - afvalwaterbehandeling - vluchtige vetzuren - sporenelementen - slib - korrels - anaerobic treatment - waste water treatment - volatile fatty acids - trace elements - sludges - granules - trace-metals - heavy-metals - sludge - binding - sediments
    The effect of the absence of trace elements on the conversion of a mixture of volatile fatty acids by a distillery anaerobic granular sludge was investigated. Two UASB reactors were operated under identical operational conditions except for the influent trace metal concentrations, during 140 days. Experiments were carried out in three periods, where different organic loading rates (OLR) were applied to the reactors
    The effect of the absence of trace elements on the conversion of a mixture of volatile fatty acids by a distillery anaerobic granular sludge Was investigated. Two UASB reactors were operated under identical operational conditions except for the influent trace metal concentrations, during 140 days, Experiments were carried out in three periods, where different organic loading rates (OLR) were applied to the reactors. The total trace metal concentration steadily decreased at a rate of 48 mug metal/g TS.d in the deprived reactor (down to 35% of their initial value). In contrast, trace metals accumulated in granules present in the control reactor. At the end of the experiment, the COD removal efficiencies were 99% and 77% for the control and deprived reactors, respectively, due to the lack of propionate conversion. Cobalt sorption experiments were carried out in order to study its speciation, and its effects on the speciation of other metals as well. A paper mill wastewater treating granular sludge was also included in the study as a comparison. Results obtained showed that the principal metal forms normally associated with any sludge are a function of each soluble metal concentration in the system, and the characteristics of the particular sludge.
    Sulfidogenic volatile fatty acid degradation in a baffled reactor
    Vallero, M.V.G. ; Lens, P.N.L. ; Bakker, C. ; Lettinga, G. - \ 2003
    Water Science and Technology 48 (2003)3. - ISSN 0273-1223 - p. 81 - 88.
    anaërobe afbraak - rioolslib - anaërobe behandeling - sulfaten - vluchtige vetzuren - afvalwaterbehandeling - anaerobic digestion - sewage sludge - anaerobic treatment - sulfates - volatile fatty acids - waste water treatment - granular sludge reactor - methanogenic bacteria - waste-water - competition - abr
    The effect of staging the sludge bed on volatile fatty acid degradation by sulfidogenic reactors was evaluated in a baffled reactor
    The effect of staging the sludge bed on volatile fatty acid degradation by sulfidogenic reactors was evaluated in a baffled reactor. In a 5.41 baffled reactor, containing three equal compartments, a volatile fatty acid (VFA) mixture (acetate: propionate:butyrate ratio 1:2:2 on COD basis; pH 8) was treated under mesophilic (30 degreesC) and sulfidogenic (COD:SO42- ratio: 0.5) conditions for 38 days. At a specific sludge loading rate of 0.50 g COD.gVSS(-1).d(-1), a COD and sulfate removal of 85% and 30%, respectively, was obtained. In the baffled reactor, staging of the sulfidogenic VFA degradation occurred. Propionate and butyrate were mainly degraded in the first compartment. Their degradation was incomplete, resulting in elevated acetate concentrations in compartment I. In the second and third compartment of the baffled reactor, a net degradation of acetate took place. Acetate was the sole substrate present in compartment III and residual acetate concentrations of about 200 mg/l were present in the effluent at a specific sludge loading of 0.50 g COD.gVSS(-1).d(-1). Sludges with different maximum specific VFA and acetate degrading activities developed in the first and second compartment. These maximal specific activities were almost equal for sludge present in compartment II and III.
    Carbon monoxide conversion by anaerobic bioreactor sludges
    Sipma, J. ; Stams, A.J.M. ; Lens, P.N.L. ; Lettinga, G. - \ 2003
    FEMS microbiology ecology 44 (2003)2. - ISSN 0168-6496 - p. 271 - 277.
    slib - anaërobe behandeling - afvalwaterbehandeling - rioolafvalwater - reductie - koolmonoxide - bioreactoren - sludges - anaerobic treatment - waste water treatment - sewage effluent - reduction - carbon monoxide - bioreactors - carboxydothermus-hydrogenoformans - methanogenic bacteria - sulfate reduction - synthesis-gas - sp-nov - growth - metabolism - oxidation - reactor - energy
    Seven different anaerobic sludges from wastewater treatment reactors were screened for their ability to convert carbon monoxide (CO) at 30 and 55degreesC
    Seven different anaerobic sludges from wastewater treatment reactors were screened for their ability to convert carbon monoxide (CO) at 30 and 55degreesC. At 30degreesC, CO was converted to methane and/or acetate by all tested sludges. Inhibition experiments, using 2-bromoethanesulfonic acid and vancomycine, showed that CO conversion to methane at 30degreesC occurred via acetate, but not via H-2. At 55degreesC, four sludges originally cultivated at 30-35degreesC and one sludge cultivated at 55degreesC converted CO rapidly into hydrogen or into methane. In the latter case, inhibition experiments showed that methane was formed via hydrogen as the intermediate. (C) 2003 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserved.
    Effect of sulfate on methanol degradation in thermophilic (55 oC) methanogenic UASB reactors
    Vallero, M.V.G. ; Lens, P.N.L. ; Paulo, P.L. ; Trevino, R.H.M. ; Lettinga, G. - \ 2003
    Enzyme and Microbial Technology 32 (2003)6. - ISSN 0141-0229 - p. 676 - 687.
    slib - anaërobe behandeling - methanol - zwavel - retentie - afvalwaterbehandeling - rioolafvalwater - sludges - anaerobic treatment - methanol - sulfur - retention - waste water treatment - sewage effluent - volatile fatty-acid - anaerobic hybrid reactor - granular sludge reactor - waste-water - ethanol degradation - reduction - digestion - velocity - hydrogen - pulp
    A thermophilic (55 degreesC) lab-scale (0.921) methanol-fed upflow anaerobic sludge bed (UASB) reactor (pH 7.0 and hydraulic retention time (HRT) of 7.5 h) was operated at chemical oxygen demand (COD) to sulfate (SO42-) ratios of 10, 5 and 0.5 during 155 days to evaluate the effects of the presence of sulfate on conversion rates, metabolic shifts and possible process disturbances
    A thermophilic (55 degreesC) lab-scale (0.921) methanol-fed upflow anaerobic sludge bed (UASB) reactor (pH 7.0 and hydraulic retention time (HRT) of 7.5 h) was operated at chemical oxygen demand (COD) to sulfate (SO42-) ratios of 10, 5 and 0.5 during 155 days to evaluate the effects of the presence of sulfate on conversion rates, metabolic shifts and possible process disturbances. Methanol was completely removed when operating at an organic loading rate of 20 g COD l(-1) day(-1) at all COD/SO42- ratios tested. At COD/SO42- ratios of 10 and 5. methanol was converted both via sulfate reduction (up to 13% when operating at a COD/SO42- of 5) and methanogenesis (85%). However, when operating at a COD/sulfate ratio of 0.5 (12 g SO42- l(-1)), the sulfate reduction efficiency strongly deteriorated, due to improper immobilization of sulfate reducing bacteria (SRB) in the sludge bed and the presence of relatively high sodium concentrations (about 6 g Na+ l(-1)) originating from supplying sulfate as its sodium salt. Complete sulfate reduction was achieved when operating at a COD/SO42- ratio of 10 (0.6 g SO42- l(-1)) and 5 (1.2 g SO42- l(-1)), corresponding to sulfate removal rates of 2 and 4 g SO42- l(-1) day(-1), respectively. Activity tests showed that methanol was syntrophically converted via H-2/CO2 by homoacetogenic bacteria, in combination with either sulfate reducing bacteria or methane producing archaea. (C) 2003 Elsevier Science Inc. All rights reserved.
    Decentralisatie en hergebruik in de publieke sanitatie. Meer duurzaamheid en grotere robuustheid
    Lettinga, G. ; Kujawa, K. ; Zeeman, G. - \ 2003
    Afvalwaterwetenschap 2 (2003)3. - ISSN 1568-3788 - p. 231 - 244.
    afvalwaterbehandeling - nieuwe sanitatie - scheiding - rioolwater - hergebruik van water - duurzaamheid (sustainability) - anaërobe behandeling - afvalwater - verzamelen - waterzuivering - waste water treatment - new sanitation - separation - sewage - water reuse - sustainability - anaerobic treatment - waste water - collection - water treatment
    In navolging van ontwikkelingen in de industriële sector is het zeer wenselijk dat ook in de publieke sector van de sanitatie wordt gekozen voor een (optimaal) decentrale aanpak. Decentrale Sanitatie en Hergebruik (DESAH) is een brongerichte benadering en sterk innovatief in de zin dat het staat voor een volstrekt ander sanitatieconcept, gericht op besparing en hergebruik van water-, energie en grondstoffen
    Bicarbonate dosing: a tool to performance recovery of a thermophilic methanol-fed UASB reactor
    Paulo, P.L. ; Lier, J.B. van; Lettinga, G. - \ 2003
    Water Science and Technology 48 (2003)6. - ISSN 0273-1223 - p. 95 - 101.
    anaërobe behandeling - afvalwaterbehandeling - methanol - reductie - ph - bicarbonaten - anaerobic treatment - waste water treatment - methanol - reduction - ph - bicarbonates - degradation
    The thermophilic-anaerobic treatment of methanol-containing wastewater in an upflow anaerobic sludge blanket (UASB) reactor, was found to be quite sensitive to pH shocks, both acid and alkaline. The results of the recovery experiments of sludge exposed to an alkaline shock, indicated that the addition or deprivation of sodium bicarbonate (NaHCO3) in the medium, plays an important role in the competition of methanogens and (homo)acetogens for methanol. In addition, caution has to be taken when using NaHCO3 for buffering methanol-containing wastewaters, since its introduction in the system will favour (homo)acetogenesis when proper conditions are not established. Based on these results, a recovery strategy for methanogenesis was proposed where bicarbonate is supplied stepwise, and the reactor is operated in a batch mode
    The thermophilic-anaerobic treatment of methanol-containing wastewater in an upflow anaerobic sludge blanket (UASB) reactor, was found to be quite sensitive to pH shocks, both acid and alkaline. The results of the recovery experiments of sludge exposed to an alkaline shock, indicated that the addition or deprivation of sodium bicarbonate (NaHCO3) in the medium, plays an important role in the competition of methanogens and (homo)acetogens for methanol. In addition, caution has to be taken when using NaHCO3 for buffering methanol-containing wastewaters, since its introduction in the system will favour (homo)acetogenesis when proper conditions are not established. Based on these results, a recovery strategy for methanogenesis was proposed where bicarbonate is supplied stepwise, and the reactor is operated in a batch mode. This strategy was found to be appropriate, i.e. the results revealed that the recovery of methanogenesis on methanol from a reactor upset or complete failure caused by pH shock is possible, even in systems where (homo)acetogens are outcompeting methanogens. The time and the number of feedings required will depend on the degree of deterioration of the sludge.
    The contribution of biotic and abiotic processes during azo dye reduction in anaerobic sludge
    Zee, F.P. van der; Bisschops, I.A.E. ; Blanchard, V.G. ; Bouwman, R.H.M. ; Lettinga, G. ; Field, J.A. - \ 2003
    Water Research 37 (2003)13. - ISSN 0043-1354 - p. 3098 - 3109.
    rioolafvalwater - anaërobe behandeling - azoverbindingen - kleurstoffen (dyes) - redoxreacties - afvalwaterbehandeling - sewage effluent - anaerobic treatment - azo compounds - dyes - redox reactions - waste water treatment - redox mediators - decolorization - bacteria - system
    Azo dye reduction results from a combination of biotic and abiotic processes during the anaerobic treatment of dye containing effluents. Biotic processes are due to enzymatic reactions whereas the chemical reaction is due to sulfide. In this research, the relative impact of the different azo dye reduction mechanisms was determined by investigating the reduction of Acid Orange 7 (AO7) and Reactive Red 2 (RR2) under different conditions. Reduction rates of two azo dyes were compared in batch assays over a range of sulphide concentrations in the presence of living or inactivated anaerobic granular sludge
    Azo dye reduction results from a combination of biotic and abiotic processes during the anaerobic treatment of dye containing effluents. Biotic processes are due to enzymatic reactions whereas the chemical reaction is due to sulfide. In this research, the relative impact of the different azo dye reduction mechanisms was determined by investigating the reduction of Acid Orange 7 (AO7) and Reactive Red 2 (RR2) under different conditions. Reduction rates of two azo dyes were compared in batch assays over a range of sulphide concentrations in the presence of living or inactivated anaerobic granular sludge. Biological dye reduction followed zero order kinetics and chemical dye reduction followed second-order rate kinetics as a function of sulfide and dye concentration. Chemical reduction of the dyes was greatly stimulated in the presence of autoclaved sludge; whereas chemical dye reduction was not affected by living or gamma-irradiated-sludge. Presumably redox-mediating enzyme cofactors released by cell lysis contributed to the stimulatory effect. This hypothesis was confirmed in assays evaluating the chemical reduction of AO7 utilizing riboflavin, representative of the heat stable redox-mediating moieties of common occurring flavin enzyme cofactors. Sulfate influenced dye reduction in accordance to biogenic sulfide formation from sulfate reduction. In assays lacking sulfur compounds, dye reduction only readily occurred in the presence of living granular sludge, demonstrating the importance of enzymatic mechanisms. Both chemical and biological mechanisms of dye reduction were greatly stimulated by the addition of the redox-mediating compound, anthraquinone-disulfonate. Based on an analysis of the kinetics and demonstration in lab-scale upward-flow anaerobic sludge bed reactors, the relative importance of chemical dye reduction mechanisms in high rate anaerobic bioreactors was shown to be small due to the high biomass levels in the reactors. (C) 2003 Elsevier Science Ltd. All rights reserved.
    Activated Carbon as an Electron Acceptor and Redox Mediator during the Anaerobic Biotransformation of Azo Dyes
    Zee, F.P. van der; Bisschops, I.A.E. ; Lettinga, G. ; Field, J.A. - \ 2003
    Environmental Science and Technology 37 (2003)2. - ISSN 0013-936X - p. 402 - 408.
    slib - koolstof - redoxreacties - verontreinigende stoffen - azoverbindingen - kleurstoffen (dyes) - anaërobe behandeling - oxidatie - afvalwaterbehandeling - sludges - carbon - redox reactions - pollutants - azo compounds - dyes - anaerobic treatment - oxidation - waste water treatment - sp strain bn6 - oxidative dehydrogenation - catalytic-oxidation - hydrogen-sulfide - fluidized-bed - reduction - sludge - decolorization - degradation - quinones
    The role of AC as redox mediator in accelerating the reductive transformation of pollutants as well as a terminal electron acceptor in the biological oxidation of an organic substrate is described. This study explores the use of AC as an immobilized redox mediator for the reduction of a recalcitrant azo dye in laboratory-scale anaerobic bioreactors, using volatile fatty acids as electron donor
    Activated carbon (AC) has a long history of applications in environmental technology as an adsorbent of pollutants for the purification of drinking waters and wastewaters. Here we describe novel role of AC as redox mediator in accelerating the reductive transformation of pollutants as well as a terminal electron acceptor in the biological oxidation of an organic substrate. This study explores the use of AC as an immobilized redox mediator for the reduction of a recalcitrant azo dye (hydrolyzed Reactive Red 2) in laboratory-scale anaerobic bioreactors, using volatile fatty acids as electron donor. The incorporation of AC in the sludge bed greatly improved dye removal and formation of aniline, a dye reduction product. These results indicate that AC acts as a redox mediator. In supporting batch experiments, bacteria were shown to oxidize acetate at the expense of reducing AC. Furthermore, AC greatly accelerated the chemical reduction of an azo dye by sulfide. The results taken as a whole clearly suggest that AC accepts electrons from the microbial oxidation of organic acids and transfers the electrons to azo dyes, accelerating their reduction. A possible role of quinone surface groups in the catalysis is discussed.
    Dark hydrogen fermentations
    Vrije, G.J. de; Claassen, P.A.M. - \ 2003
    In: Bio-methane & bio-hydrogen : status and perspectives of biological methane and hydrogen production / Reith, J.H., Wijffels, R.H., Petten : Dutch Biological Hydrogen Foundation - ISBN 9789090171654 - p. 103 - 123.
    bio-energie - waterstof - anaërobe behandeling - biomassa - bioenergy - hydrogen - anaerobic treatment - biomass
    The production of hydrogen is a ubiquitous, natural phenomenon under anoxic or anaerobic conditions. A wide variety of bacteria, in swamps, sewage, hot springs, the rumen of cattle etc. is able to convert organic matter to hydrogen, CO2 and metabolites like acetic acid, lactate, ethanol and alanine. In general, these bacteria live in the close vicinity of other bacteria which consume these metabolites, including hydrogen, producing their own endproducts like methane and CO2. In this way, a stable ecosystem is formed where potential feedback inhibition of the hydrogen producers by hydrogen, is annulled by the action of the hydrogen consumers. In view of the design of a bioprocess for the production of hydrogen from biomass, extreme thermophilic anaerobic bacteria have been selected because of their high yield with respect to hydrogen production. The yield is reported to be approximately 83-100¿f the maximal theoretical value of 4 mol hydrogen/mol glucose, in contrast to the strict anaerobic Clostridia which produce hydrogen with an approximate yield of 2 mol/mol and the facultative anaerobes which show a H2 yield of less than 2. Besides optimal H2 molar yields, high hydrogen production rates are needed. Product formation appeared to be dependent on cell densities. Thermophiles usually grow to low densities and, therefore production rates are expected to be low. High production rates are reported for Clostridia and Enterobacter of maximal 23 and 58 mmol/L.h, respectively. Hydrogen fermentations by co- and mixed cultures showed production rates of approximately 30-50 mmol/L.h.
    Towards sustainable and robust on-site domestic wastewater treatment for all citizens
    Mgana, S. - \ 2003
    Wageningen University. Promotor(en): Gatze Lettinga, co-promotor(en): W.T.M. Sanders. - [S.I.] : S.n. - ISBN 9789058087645 - 95
    afvalwaterbehandeling - anaërobe behandeling - haalbaarheidsstudies - tropen - waste water treatment - anaerobic treatment - feasibility studies - tropics

    In most developing countries commonly practiced domestic wastewater treatment systems predominantly constitute anaerobic treatment process. The anaerobic treatment units mostly installed are on-site at residential dwellings.

    However the commonly installed units, viz., traditional pit latrines and septic tanks are in fact 'low-rate' anaerobic pre-treatment units and are associated with inefficiency, poor maintenance and groundwater pollution. Moreover since most poor communities, who constitute the majority in the developing countries' populations could afford these types of anaerobic pre-treatment units, their numbers have also grown to unmanageable proportions. Consequently the demand for effective but low cost wastewater treatment facilities for developing countries is indisputably great.

    On the basis of already available technical information concerning the Upflow Anaerobic Sludge Bed (UASB) reactor performance a wastewater treatment system based on the UASB reactor can lead to a compact, effective and low cost community on-site pre-treatment unit for tropical wastewaters. However the performance of these systems in an actual community on-site situation has so far not been investigated. This thesis therefore investigates the performance and feasibility of using the UASB reactor for the pre-treatment of wastewater under the conditions that arise at community level in tropical regions, viz. highly varying organic and hydraulic loads, but low variation in temperature.

    On-site pilot scale UASB reactors were configured and operated in parallel at community level for the purpose of acquiring performance data. All the reactors were operated in gravity flow mode at ambient tropical temperature of 25 - 34 ºC. The wastewater in the study area - community level - was highly biodegradable with an average ratio COD:BOD 5 of 1.52 at a standard deviation of 0.13. The wastewater characteristic was highly variable. A 1277-day monitoring duration of the wastewater grab samples has shown that the values of organic loads (with standard deviation in brackets), in terms of COD tot , and COD ss , were 529.4 (544.6) and 264.4 (448.4) mg/L respectively.

    A conventional pilot single-step community on-site UASB reactor (volume: 1.5 m 3, height: 1.7 m) was operated over three and a half years at an average hydraulic retention time of 6.2 (4.92). The performance data obtained via regular monitoring of the treatment unit showed a declining removal efficiency over time with respect to COD total , which likely can be attributed to the increasing rate at which biogas was produced along with the growth of sludge bed and the presence of floating sludge. As a result the removal of dispersed sludge particles becomes poorer, which likely is reinforced by the possible 'less' optimal dimensions and design of the Gas-Solids-Separator (GSS) device. The average removal efficiency on COD tot basis was 64 percent. However a study of a parallel pilot two-step community on-site UASB reactor configuration gave more promising results. The two-step UASB pre-treatment unit in this research refers to two UASB reactors connected in series, viz. a first 2m high 1.8m 3UASB reactor put in front of a second 1m high 0.852 m 3UASB reactor. The second-step UASB reactor is a recipient of effluent including washouts from the first-step UASB reactor The average organic loads of the wastewater imposed to the system with respect to COD fractions COD tot , COD ss , COD col and COD sol were 537.2 (165.3), 189.9 (109.5), 127.4 (75) and 223.4 (108.8) respectively. The investigations were conducted over a period of 630 days. The overall removal efficiency obtained on the basis of the distinguished COD fractions was far better than for the individual reactors, i.e efficiencies for COD tot , COD ss , COD col and COD sol , were respectively 68.7 (16.7), 51.2 (41.8), 62.1(38.2), and 71.8 (30.5) %. The imposed overall HRT was 7.4 (1.6) (i.e. 5 + 2.4) hours. The advantages of the two-step UASB reactor configuration include 1) the distinct higher overall removal efficiency of the anaerobic pre-treatment system 2) the higher sludge age 3) the higher reliability of the anaerobic pre-treatment process 4) the two reactors can separately be operated in case of technical problems.

    Integrated Application of the UASB Reactor and Ponds for Domestic Sewage Treatment in Tropical Regions
    Cavalcanti, P.F.F. - \ 2003
    Wageningen University. Promotor(en): Gatze Lettinga. - [S.I.] : S.n. - ISBN 9789058088185 - 139
    rioolslib - afvalverwerking - brazilië - anaërobe behandeling - sewage sludge - waste treatment - brazil - anaerobic treatment

    Waste stabilization ponds are widely applied for domestic sewage treatment in Brazil. The main objective of conventional waste stabilisation ponds (WSP's) is, nomen est omen , to remove the organic material from wastewater. To achieve this objective, a quite long liquid retention time ( R h ) is required: even under the favourable conditions of the tropics (high temperature, sunshine) a minimum liquid retention time of 20 to 30 days is necessary. It is well established that the optimal ponds configuration for domestic sewage treatment consists of a serial system composed of an anaerobic pond, followed by a partially aerobic (facultative) and one or more predominantly aerobic (maturation) ponds.

    By substituting the anaerobic pond by an efficient high rate anaerobic reactor like the Up Flow Anaerobic Sludge Bed (UASB) reactor, the pond receiving the effluent of this reactor - an polishing pond - will receive a relatively very low organic load and therefore the design criteria for this pond are very similar to those for maturation ponds, that is the polishing pond is designed for pathogen and/or nutrient removal.

    In semi-arid regions, like the North-East of Brazil, the use of treated sewage for irrigation water is an ecologically sound solution if precautions are taken to avoid contamination of the workers and of the consumers of the produced crops. According to the very sticky World Health Organization (WHO) standards for unrestricted irrigation, the helminth concentration must be less than 1 per litre and the faecal coliform ( FC ) concentration less than 10 3colony forming unit (CFU) per 100 ml. On the other hand, other important fact in design of pond systems is the evaporation from the pond needs to be minimal, and consequently the pond area must be as small as possible. When UASB effluent (with low organic material and suspended solids concentrations) is post-treated in polishing ponds, these systems can be designed specifically for FC removal. For that reason, their surface area can be kept smaller than that of conventional ponds, designed for organic material removal. For reducing the liquid retention time (and surface area) of a polishing pond it is necessary to minimize the degree of mixing as much as possible, so that the hydraulic regime approaches a plug flow regime.

    This thesis deals with aspects of design, performance and operation of sewage treatment systems consisting of an UASB reactor followed by a polishing pond. The thesis is directed to an experimental pilot plant investigation for assessing design and operation parameters with respect to the performance of the UASB reactor followed by post-treatment in different configurations of polishing ponds. With such a treatment system it was possible to produce an effluent that can be well used for unrestricted irrigation. The advantage of the system is that it allows a substantial reduction in the required surface area compared to the area required in conventional waste stabilization pond systems.

    As far as UASB reactor design concerned, it was shown that the phase separator design is of paramount importance to the performance of the system. The addition of parallel plates to the conventional phase separator could double the treatment capacity of the UASB reactor. The experimental investigation also showed that the sludge age and not the liquid retention time is the fundamental operational parameter of the UASB reactor: UASB reactors with different liquid retention times but the same sludge age will tend to have the same efficiency.

    An important aspect of UASB operation is the discharge of excess sludge. In this thesis a method was developed to estimate the frequency of excess sludge discharge as well as the optimal fraction of the total that can be discharged. It was shown that discharges of less than 50% of the sludge mass had a small and transitory effect on the UASB performance.

    Polishing ponds were operated both with a continuous and sequential batch feeding. Based on the experimental results of the investigations, relevant operational and conceptual aspects were elucidated and elements for dimensioning and designing polishing ponds could be provided.

    It was shown that the required liquid retention time for reduction of the BOD5 and TSS concentrations to a virtually constant value only amounts to about 3 days, which is very short i.e. a factor 7 to 10 times shorter than the liquid retention time (25 - 30 days) in conventional WSP's. In this investigation the FC concentration in the digested sewage was of the order of 10 7per 100 ml, so that the required removal efficiency for unrestricted irrigation ( FC < 10 3CFU /100 ml) was 99.99 % (4 log units). By using the value of the experimentally determined decay constant (2.0 to 2.2 day -1 at a depth of 0.65 m) the minimum time for this removal efficiency was calculated at 4 to 5 days for exponential decay. However the experimentally observed removal efficiency in a flow-through pond was much lower than expected on the basis of first order kinetics (exponential decay). This was attributed to the fact that partial mixing could not be avoided, even though the polishing pond was specifically designed to approach the plug flow regime as closely as possible. For this reason a minimum liquid retention time of about 10 days was required for a removal efficiency of 99.99 %.

    Mixing in continuous reactors like polishing ponds was quantified by determining the residence time distribution of the liquid by applying a slug of a tracer in the influent and observing its concentration as a function of time in the effluent. The experimental data obtained in these investigations showed that even in the pond that was carefully designed and operated to avoid mixing as much as possible, the dispersion number was of the order of 0.1 to 0.2, which means that mixing intensity was moderate. The tracer studies also revealed a surprisingly high dead volume fraction in the pond. When the values of the dispersion numbers and the dead volume fractions were used to calculate the theoretical faecal coliform removal efficiency in the pond from the Wehner and Wilhelm equation, it was established that there was a good correlation between theory and experimental data.

    Exponential decay for a first order process like FC removal can be guaranteed in a batch reactor. In this thesis the behaviour of ponds fed with sequential batches (SB) of anaerobically treated sewage was also evaluated. It was shown that the reduction in the FC concentration, was a good approximation, to the exponential decay of a first order process until a value of 1000 CFU /100 ml is attained, so that a very high removal efficiency (> 99.99%) of FC was obtained in a very short period of 4 to 5 days, as foreseen by theory for the experimental decay constant of 2.0 to 2.2 day -1. During this period complete elimination of helminth eggs also occurred. In addition, due to the efficient pre-treatment, an aerobic environment prevailed in the sequential batch (SB) ponds and a substantial further reduction of the BOD5 and TSS concentrations took place. Thus a final effluent was produced in ponds with a liquid retention time of only 4 to 5 days with a quality that complies with WHO standards for unrestricted irrigation. The liquid retention time required in a SB pond was only about half of the value for a flow-through polishing pond, so that its application leads to a reduction of the required pond area by a factor of 2. In conventional waste stabilisation pond systems the R h time under tropical climate conditions is of the order of 25 days, which is a factor 5 to 6 times greater than in polishing ponds operated in sequential batch mode for the production of an effluent for unrestricted irrigation.

    Other important finding of the investigations was that the rate of bottom sludge accumulation in polishing ponds remained much smaller than the values reported for conventional waste stabilization ponds, even though no sludge was discharged from the UASB reactor. The reduced bottom sludge accumulation has an important practical advantage: the frequency of desludging operation will be much lower than in anaerobic ponds and this operation may be unnecessary during the useful life span of the polishing pond.

    Optimisation of sulphate reduction in a methanol-fed thermophilic bioreactor
    Weijma, J. ; Bots, E.A.A. ; Tandlinger, G. ; Stams, A.J.M. ; Hulshoff Pol, L.W. ; Lettinga, G. - \ 2002
    Water Research 36 (2002). - ISSN 0043-1354 - p. 1825 - 1833.
    afvalwaterbehandeling - anaërobe behandeling - sulfaten - methanol - reductie - slib - waste water treatment - anaerobic treatment - sulfates - methanol - reduction - sludges
    Several methods were tested to optimise sulphate reduction and minimise methane formation in thermophilic (65°) expanded granular sludge bed reactors fed with a medium containing sulphate and methanol. Lowering the pH from 7.5 to 6.75 resulted in a rapid decrease of methane formation and a concomitant increase in sulphate reduction. The inhibition of methane formation was irreversible on the short-term. Lowering the COD/SO42- ratio (COD: chemical oxygen demand) from 6 to 0.34 (g/g) rapidly favoured sulphate reduction over methanogenesis. Continuous addition of 2 g L-1 2-bromoethanesulphonate was ineffective as complete inhibition of methanogenesis was obtained only for two days. Inhibition of methanogens by sulphide at pH 7.5 was only effective when the total sulphide concentration was above 1200 mg S L-1. For practical applications, a relatively short exposure to a slightly acidic pH in combination with operating the reactor at a volumetric methanol-COD loading rate close to the maximum volumetric sulphide-COD formation rate.
    Interspecies electron transfer in suspended and aggregated methanogenic propionate-degrading consortia
    Bok, F.A.M. de; Plugge, C.M. ; Stams, A.J.M. - \ 2002
    In: Granulation and auto-immobilisation processes in wastewater treatment : Farewell seminar Dr. Ir. Look Hulshoff Pol October 11, 2002, Wageningen, the Netherlands / van Lier, J.B., Lexmond, M., Vos, H., - p. 47 - 59.
    afvalwaterbehandeling - anaërobe behandeling - slib - immobilisatie - microbiële afbraak - methaan - oxidatie - elektronenoverdracht - formiaten - propionaten - waste water treatment - anaerobic treatment - sludges - immobilization - microbial degradation - methane - oxidation - electron transfer - formates - propionates
    Propionate is a key intermediate in the conversion of complex organic matter under methanogenic conditions. Oxidation of propionate to acetate is energetically unfavorable under standard conditions. Therefore, micro organisms are only able to gain energy from this conversion if the concentrations of the products, and H2 or formate in particular, are kept low by methanogens. This implies that obligate syntrophic consortia are required for propionate oxidation. Because of their poor energetics and their role in methanogenic conversions, syntrophic propionate oxidizing bacteria have gained quite some attention in the past. The authors present an overview of what is currently know about these organisms and pay special attention to the role of H2 and formate in interspecies electron transfer during syntrophic propionate oxidation
    Start-up of a thermophilic methanol-fed UASB reactor: change in sludge characteristics
    Paulo, P.L. ; Jiang, B. ; Roest, K. ; Lier, J.B. van; Lettinga, G. - \ 2002
    Water Science and Technology 45 (2002). - ISSN 0273-1223 - p. 145 - 150.
    slib - korrels - anaërobe behandeling - afvalwaterbehandeling - methanol - rioolafvalwater - sludges - granules - anaerobic treatment - waste water treatment - methanol - sewage effluent
    Experiments were performed to study the change in sludge characteristics and sludge granulation during the start-up of a thermophilic methanol-fed upflow anaerobic sludge bed (UASB) reactor. The laboratory scale reactor, was inoculated with thermophilic granular sludge and operated at 55 degrees C over 130 days at organic loading rates (OLR) varying from 2.7 to 47 gCOD.L(-1).d(-1). Physical characterisation was performed for both the seed and the cultivated sludge. Results demonstrated that a good quality, well settleable granular sludge was cultivated and retained in the reactor, allowing an OLR of 47 gCOD.L.d(-1) with 93% of methanol removal, where 79% was converted into methane. Using a community analysis of the cultivated consortia, high numbers of rod-shaped hydrogenotrophic methanogens were enumerated. Biomass washout coincided with a high specific gas load, but was not detrimental to the system in the conditions tested.
    Modelling the competition between sulphate reducers and methanogens in a thermophilic methanol-fed bioreactor
    Spanjers, H. ; Weijma, J. ; Abusam, A. - \ 2002
    Water Science and Technology 45 (2002)10. - ISSN 0273-1223 - p. 93 - 98.
    rioolslib - afvalwaterbehandeling - methanol - sulfaten - reductie - anaërobe behandeling - afvalwater - micro-organismen - sewage sludge - waste water treatment - methanol - sulfates - reduction - anaerobic treatment - waste water - microorganisms
    Sulphate can be removed from wastewater by means of biological anaerobic reduction to sulphide. The reduction requires the presence of a substrate that can serve as an electron donor. Methanol a suitable electron donor for sulphate reduction under thermophilic conditions. In an anaerobic system containing methanol and sulphate, acetogenic bacteria (AB) and methanogenic archaea (MA) compete with sulphate reducing bacteria (SRB) for methanol or its degradation intermediates. Previously obtained results indicate that at 65 degrees C SRB and MA mainly compete for the intermediate hydrogen instead of methanol. For efficient use of methanol as electron donor for sulphate reduction it is important that for the treatment of sulphate wastewater in an anaerobic reactor SRB out-compete MA. The mechanisms that determine the outcome of the competition are, however, not well understood. This paper describes a model based on growth kinetics of methanol-oxidising AB, and hydrogen-consuming SRB and MA, that can describe the competition between SRB and MA in a methanol-fed bioreactor. We present the model and its calibration using experimental data, and we discuss its shortcomings and suggest possible improvements.
    Hydrolysis kinetics of dissolved polymer substrates
    Sanders, W.T.M. ; Zeeman, G. ; Lettinga, G. - \ 2002
    Water Science and Technology 45 (2002)10. - ISSN 0273-1223 - p. 99 - 104.
    afvalwaterbehandeling - anaërobe behandeling - kinetica - substraten - hydrolyse - biodegradatie - anaërobe afbraak - waste water treatment - anaerobic treatment - kinetics - substrates - hydrolysis - biodegradation - anaerobic digestion
    In this paper, the relation between the hydrolysis rate of dissolved polymer substrates and sludge concentration was investigated in two ways, viz. by laboratory experiments and by computer simulations. In the simulations, the hydrolysis of dissolved polymer components was regarded as a general depolymerisation process in which the bonds of the parent molecule break randomly until only monomer and dimer components remain. The results illustrate that for the hydrolysis of dissolved polymer substrates the enzyme activity is the rate-limiting factor. Moreover, a general depolymerisation process can describe the enzymatic hydrolysis of these components.
    Competition for H2 between sulfate reducers, methanogens and homoacetogens in a gas-lift reactor
    Weijma, J. ; Gubbels, F. ; Hulshoff Pol, L.W. ; Stams, A.J.M. ; Lens, P.N.L. ; Lettinga, G. - \ 2002
    Water Science and Technology 45 (2002). - ISSN 0273-1223 - p. 75 - 80.
    slib - rioolslib - waterstof - afvalwaterbehandeling - substraten - kinetica - sulfaten - anaërobe behandeling - sludges - sewage sludge - hydrogen - waste water treatment - substrates - kinetics - sulfates - anaerobic treatment
    Reported values for growth kinetic parameters show an order in competitivity of heterotrophic sulfate reducing bacteria>methanogens>homoacetogens for the substrate hydrogen. This order suggests that methanogens can succesfully compete with consortia of heterotrophic SRB and homoacetogens when H2/CO2 is present as sole substrate. However, we found in experiments using gas-lift reactors inoculated with anaerobic sludge and fed with H2/CO2 and sulfate, that heterotrophic sulfate reduction rapidly and completely outcompeted methanogenesis, whereas a low amount of acetate was formed. Thus, in disagreement with the above competitivity order, hydrogen is more readily consumed by homoacetogenesis than by methanogenesis, indicating that the competition is not kinetically determined. The superior settling velocity of sulfidogenic-acetogenic sludge compared to that of methanogenic sludge suggests that the former sludge is better retained, which can explain the predominance of sulfate reduction/homoacetogenesis over methanogenesis.
    Optimalisatie van de anaërobe vergisting van complex afval(water) : de anaërobe hydrolyse van vetten, koolhydraten en eiwitten
    Sanders, W.T.M. ; Zeeman, G. - \ 2002
    Afvalwaterwetenschap 1 (2002)4. - ISSN 1568-3788 - p. 55 - 67.
    afvalwaterbehandeling - anaërobe afbraak - waterzuivering - optimalisatie - anaërobe behandeling - afvalwater - hydrolyse - waste water treatment - anaerobic digestion - water treatment - optimization - anaerobic treatment - waste water - hydrolysis
    Complex afval(water), zoals rioolwater, slachthuisafvalwater, mest of afvalwater van de aardappelverwerkende industrie bevat organische polymeren, zoals eiwitten, koolhydraten en vetten. Deze polymeren komen in de vorm van deeltjes, opgeloste polymeren en geëmulgeerd in het afval(water) voor. Een samenvatting van het onderzoek op het gebied van de hydrolyse van complex afval(water)
    Kringloopsluiting in de papierfabriek door middel van thermofiele proceswaterzuivering
    Vogelaar, J.C.T. ; Klapwijk, A. ; Lier, J.B. van - \ 2002
    Afvalwaterwetenschap 1 (2002)4. - ISSN 1568-3788 - p. 25 - 38.
    afvalwaterbehandeling - afvalwater - warmte - geactiveerd slib - aërobe behandeling - voorbehandeling - anaërobe behandeling - pulp- en papierwarenindustrie - waterzuivering - waste water treatment - waste water - heat - activated sludge - aerobic treatment - pretreatment - anaerobic treatment - pulp and paper industry - water treatment
    Dit artikel beschrijft het onderzoek naar de thermofiele aerobe nazuivering van anaeroob voorgezuiverd papier proceswater. In batch experimenten vond een proceswater karakterisering plaats met mesofiel en thermofiel actief slib. In tweede instantie werd de toepasbaarheid van een conventioneel actiefslibsysteem onder thermofiele condities bestudeerd
    Effect of high salinity on the fate of methanol during the start-up of thermophilic (55°C) sulfate reducing reactors
    Vallero, M.V.G. ; Hulshoff Pol, L.W. ; Lens, P.N.L. ; Lettinga, G. - \ 2002
    Water Science and Technology 45 (2002)10. - ISSN 0273-1223 - p. 121 - 126.
    anaërobe behandeling - afvalwaterbehandeling - methanol - reductie - natriumchloride - sulfaten - rioolafvalwater - slib - anaerobic treatment - waste water treatment - methanol - reduction - sodium chloride - sulfates - sewage effluent - sludges
    Two 6.5 L lab-scale upflow anaerobic sludge bed (UASB) reactors were operated at 55°C fed with methanol as the sole electron and carbon source and in excess of sulfate (COD/SO42- of 0.5) in order to investigate the effect of high wastewater salinity on the start-up period. The first reactor (UASB I) was operated without NaCl addition, while the second reactor (UASB II) was fed with 25 g.L-1 of NaCl in the first 13 days of operation. Successful start-up of UASB I was achieved, with full methanol conversion (100␎limination) to methane gas (methane production rate up to 3.66 gCOD.L-1.day-1). Despite the detection of sulfide from day 15 onwards in UASB I, methane was the main mineralization product when operating at an organic loading rate (OLR) of 5 gCOD.L-1.day-1 and a hydraulic retention time (HRT) of 10 hours. Sulfide and acetate started to be produced after salt omission from the influent in UASB II at day 13, with no detection of methane. Acetate was the main product when operating at an OLR of 10 gCOD.L-1.day-1 and HRT of 6.5 hours in both reactors. Apparently, the methane producing bacteria (MPB) are the trophic group most sensible to the NaCl shock.
    Anaerobic pre-treatment of strong sewage : a proper solution for Jordan
    Halalsheh, M.M. - \ 2002
    Wageningen University. Promotor(en): G. Lettinga; G. Zeeman; M. Fayyad. - S.l. : S.n. - ISBN 9789058086891 - 113
    anaërobe behandeling - rioolafvalwater - jordanië - anaerobic treatment - sewage effluent - jordan

    The main objective of this research was to assess the feasibility of applying low cost anaerobic technology for the treatment of relatively high strength sewage of Jordan using two-stage and one-stage UASB reactors operated at ambient temperatures. The wastewater produced in Jordan is characterised by a high concentration of COD tot with averages higher than 1200 mg/l and with a large fraction in the suspended form (65-70%). The average wastewater temperature fluctuates between 18 and 25 oC for winter and summer respectively.

    The sludge bed in the UASB reactors was first simulated using CSTR systems. The objective was to study the digestion process as a function of temperature and SRT. Of particular interest was the assessment of the sludge potential to form a scum layer in relation to the degree of sludge digestion. The results revealed that methanogenesis starts only at an SRT between 30-50 days for reactors operated at 15 oC, while it starts at an SRT between 5-15 days for reactors operated at 25 oC. Both SRT and temperature affect the extent of scum formation. The degree of digestion has a clear effect on the concentration of lipids. Latter compounds tend to adsorb on sludge particles and have a strong tendency for floatation. However, it was found that sludge with a high scum forming potential only will produce scum in the presence of gas production. Based on these results scum formation in UASB systems could be prevented either by attempting to achieve a 'complete' conversion of lipids (one stage conventional UASB reactor with long SRT) or by preventing the evolution of gas production. The later could be achieved by designing a two stage UASB reactor, where the first stage mainly aims at the entrapment and partial hydrolysis of solids, while the second stage could act as a methanogenic reactor for the final conversion of the hydrolysed materials from the first stage.

    A 96-m 3two-stage UASB reactor was built at the location of Khirbit As-Samra treatment plant, which treats wastewater produced by 2.2 million inhabitants -almost half of the population of Jordan-. Operating the reactor for a year at 8+6 hrs HRTs for the first and the second stages respectivley resulted in average COD tot and COD ss removal efficiencies of 51% and 60% respectively for the first stage with no significant effect of temperature. The second stage had a poor performance and most of the treatment was attributed to the first stage. Biogas was produced in the first stage and resulted in heavy scum formation and sludge washout from the first to the second reactor, which affected the performance of the latter. Moreover, sludge produced in the first stage needs further stabilisation, particularly during wintertime.

    The performance of the first stage could be improved by enhancing solids removal using an AF reactor instead of an UASB reactor. An AF reactor was operated at an HRT of 4.6 hrs at 25 oC. The media in the filter are reticulated polyurethane foam sheets, which were vertically oriented in the reactor. Sludge was discharged regularly from the reactor. The results showed an average COD ss removal efficiency of 71%. The

    Operating the first stage reactor (60 m 3) as a conventional UASB reactor at an HRT of 24 hr showed an average removal efficiency of 62% for COD tot during summer. The removal efficiency dropped to 51% during wintertime. However, the effluent suspended solids were stabilised with a VSS/TSS ratio around 0.50 all over the year. Moreover, the sludge developing in the one stage reactor is well stabilised and exerts an excellent settlability. Regular sludge discharge from the one stage UASB reactor had no significant effect on the performance in terms of COD tot removal efficiency; however, sludge discharge most likely resulted in a more stable performance of the system, as wash out of scum layer sludge would remain low. The removal of the stabilised solids from the effluent of the UASB reactor will provide an average total COD removal efficiency between 87-93%.

    Thermophilic aerobic post treatment of anaerobically pretreated paper process water
    Vogelaar, J.C.T. - \ 2002
    Wageningen University. Promotor(en): G. Lettinga; A. Klapwijk; J.B. van Lier. - S.l. : S.n. - ISBN 9789058087133 - 152
    pulp- en papierwarenindustrie - pulpperswater - anaërobe behandeling - warmtebehandeling - aërobe behandeling - pulp and paper industry - pulp press water - anaerobic treatment - heat treatment - aerobic treatment

    Thermophilic waste- or process water treatment increases in importance as industries shift from end-of-pipe treatment towards integrated process water treatment. The need for process water treatment becomes evident as the levels of pollutants in industrial water circuits need to be controlled whereas the intake of fresh water generally diminishes. In the paper and board industry, high process water temperatures prevail and thus water treatment needs to take place under thermophilic conditions. In many cases, an anaerobic pretreatment method can be used but aerobic post treatment is required for polishing of the anaerobic effluent. This thesis describes research in which the aerobic post treatment of anaerobic effluent of a board mill was investigated under thermophilic conditions.

    As a boundary condition for aerobic conversions, sufficient oxygen needs to be transferred from the gas phase to the liquid in which the bioconversion takes place. It was shown that although the oxygen saturation concentration decreases with a rise in temperature, this effect is fully compensated by the increased oxygen diffusion rate with the same temperature increase. The overall oxygen transfer rate thus remains constant in the temperature range of 20-55 °C.

    Post treatment of anaerobic effluent in activated sludge reactors revealed several fundamental differences between mesophilic and thermophilic treatment. Firstly, batch and continuous experiments showed a lesser removal of complex soluble COD under thermophilic conditions when compared to mesophilic reference experiments. This could not be attributed to a higher production of soluble microbial products (SMP) at elevated temperatures. It is therefore expected that thermophilic biomass is unable to oxidize the same variety of complex soluble components as the mesophilic biomass is capable of.

    Secondly, thermophilic effluents are often cloudy while effluents of mesophilic activated sludge reactors are generally clear. This is caused by smaller cohesion forces within thermophilic activated sludge flocs resulting in a higher sensivity towards shear forces and smaller floc sizes. Furthermore, fewer colloidal particles from the influent are adsorbed on the thermophilic sludge flocs and are washed out with the effluent. However, a clear thermophilic effluent can be obtained provided the influent contains little colloidal material.

    The underlying causes for the weaker cohesion forces within the flocs are still unclear. The absence of protozoa at 55 °C was shown to be of minor importance regarding the effluent turbidity and could not account for this effect. Binding of hydrophobic pollutants on a hydrophobic surface was hardly affected by temperature and could not explain the observed effects either. Based on calculations using the DLVO theory it was shown that bacterial exo-polymers are of crucial importance in the flocculation process. These interactions are highly temperature dependant and are therefore expected to be the underlying cause for the differences in flocculation behavior.

    Besides differences in removal efficiencies and flocculation behavior, also the kinetics of mesophilic and thermophilic activated sludge treatment differ. The maximum growth (and thus conversion rate) of biomass cultivated at 55 °C was a factor 1.4 higher than for a similar type of biomass cultivated at 30 °C. Decay rates are doubled with the same temperature increase whereas the gross biomass yields were similar. As a result, higher substrate conversion rates can be obtained under thermophilic conditions provided that a high concentration of thermophilic biomass is cultivated in the reactor by application of a high organic loading rate.

    These kinetic advantages are however of little use when polishing the effluent of an anaerobic bioreactor. Under thermophilic conditions biomass growth will be limited since the organic loading rate is restricted by the need to retain and convert particulates from the anaerobic effluent and by the absence of readily biodegradable COD. Furthermore, biomass decay rates have doubled under thermophilic conditions. The combination of these factors diminishes the amount of active biomass in the thermophilic reactor and can not be compensated fully by the intrinsic higher conversion rates. Overall conversion rates in a thermophilic bioreactor can thus be lower as compared to a mesophilic reference system, depending on the applied loading rates.

    Nevertheless, for application in the board industry these disadvantages can be dealt with as the water quality demands are relatively low. Additional treatment methods are however required in case higher water quality demands prevail.

    Anaerobic pre-treatment of sewage under low temperature (15 [degrees] C) conditions in an integrated UASB-digester system
    Mahmoud, N.J.A.H. - \ 2002
    Wageningen University. Promotor(en): G. Lettinga; H.J. Gijzen; G. Zeeman. - S.l. : S.n. - ISBN 9789058086617 - 128
    rioolslib - anaërobe behandeling - palestina - sewage sludge - anaerobic treatment - palestine

    The main objective of this thesis was to amend the UASB by the means of incorporating a digester for anaerobic sewage treatment in the Middle East region.

    A literature search of the various parameters that mightaffect the solid liquid separation process by filtration through the sludge bed of a UASB has been elaborated. The overall output of this study includes, literature review, structuring this field of science and highlighting fields where research is needed.

    The investigation of sewage characteristics in Palestine revealed that the sewage is of high strength and low temperature during wintertime ca . 15 ºC. Accordingly, prediction based on model calculations revealed that the application of the one stage UASB reactor for sewage treatment in Palestine is only possible when designed at a HRT of more than 22 hours. Alternatively, a novel technology consisting of a Digester complementing a UASB, namely UASB-Digester system, was proposed.

    The results of primary sludge stabilisation in CSTRs revealed that the major achievement of sludge stabilisation occurred at SRT³10 and 15 days at process temperatures of 35 and 25 ºC, respectively. The sludge dewatering results showed the existence of optimal SRT at 20 and 15 days at process temperatures of 25 and 35 ºC, respectively. While, the sludge settling is not affected by digestion.

    Running a pilot-scale one stage UASB and a UASB-Digester system on sewage from the village of Bennekom, The Netherlands validated the technical viability of the UASB-Digester system. The UASB reactor was operated at an HRT of 6 hours and temperature of 15°C, the wintertime sewage temperature in Palestine, and the digester was operated at 35°C. The achieved removal efficiencies of total COD, suspended COD, colloidal COD and dissolved COD of respectively 66, 87, 44 and 30 in the UASB-Digester is significantly higher than the respectively 44, 73, 3 and 5 achieved in the one stage UASB and as high as those reported for tropical countries. The conversion in the UASB of the UASB-Digester system is substantially higher than in the one stage, viz. the percentage methanogenesis of the influent COD were 21 and 44% in the first and second systems, respectively. The sludge produced from the UASB of the UASB-Digester system is substantially lower and more stable as compared with the sludge in the one stage UASB reactor. The settleability of the sludge of the UASB, UASB of the UASB-Digester system and the digester sludges reveals high settleability with no influence of the digestion conditions. The wasted sludge from the UASB of the UASB-Digester system is better dewaterable as compared to that of the UASB reactor.

    Anaerobic azo dye reduction
    Zee, F.P. van der - \ 2002
    Wageningen University. Promotor(en): G. Lettinga; J.A. Field. - S.l. : S.n. - ISBN 9789058086105 - 142
    anaërobe behandeling - azoverbindingen - kleurstoffen (dyes) - redoxreacties - antrachinonen - anaerobic treatment - azo compounds - dyes - redox reactions - anthraquinones

    Azo dyes, aromatic moieties linked together by azo (-N=N-) chromophores, represent the largest class of dyes used in textile-processing and other industries. The release of these compounds into the environment is undesirable, not only because of their colour, but also because many azo dyes and their breakdown products are toxic and/or mutagenic to life. To remove azo dyes from wastewater, a biological treatment strategy based on anaerobic reduction of the azo dyes, followed by aerobic transformation of the formed aromatic amines, holds promise. However, the first stage of the process, anaerobic azo dye reduction, proceeds relatively slow. Therefore, this thesis research aimed at optimising anaerobic azo dye reduction, by studying the reaction mechanism and by consequently applying the obtained insights.

    In this thesis it is shown that non-adapted anaerobic granular sludge has the capacity to non-specifically reduce azo dyes. As there was no correlation between a dye's reduction rate and its molecular characteristics (i.e. its size and its number of sulphonate groups and other polar substituents), it is unlikely that the mechanism of azo dye reduction involves cell wall penetration. Moreover, the presence of bacteria is not a prerequisite: azo dyes can also be reduced by sulphide in a purely chemical reaction. As dye containing wastewater usually contains sulphate and other sulphur species that will be biologically reduced to sulphide during treatment in anaerobic bioreactors, azo dye reduction will be a combination of biotic and abiotic processes. However, it was demonstrated that under normal conditions in high-rate anaerobic bioreactors (high sludge content, moderate sulphide levels), chemical azo dye reduction by sulphide hardly contributes to the overall reaction. Anaerobic azo dye reduction is therefore mainly a biological process, either a direct enzymatically catalysed reaction involving non-specific enzymes or a reaction with enzymatically reduced electron carriers. Azo dye reduction by sludge that had not earlier been exposed to dyes was found to relate to the oxidation of endogenous substrate and, especially, to the oxidation of hydrogen when present in bulk concentrations. Enrichment was required for the utilisation of electrons from volatile fatty acids for dye reduction.

    Examination of the reduction of twenty chemically distinct azo dyes by anaerobic granular sludge revealed a large variation in the reaction rates. Especially reactive azo dyes with triazyl reactive groups were slowly reduced. For these common occurring reactive dyes, long contact times may be necessary to reach a satisfying extent of decolourisation. Consequently, they pose a serious problem for applying high-rate anaerobic treatment as the first stage in the biological degradation of azo dyes. However, this problem can be overcome by using redox mediators, compounds that speed up the reaction rate by shuttling electrons from the biological oxidation of primary electron donors or from bulk electron donors to the electron-accepting azo dyes.

    It was observed that one of the constituent aromatic amines of the azo dye Acid Orange 7 had an autocatalytic effect on the dye's reduction, probably by acting as a redox mediator. Other compounds, e.g. the artificial redox mediator anthraquinone-2,6-disulphonate (AQDS), a compound that is known to catalyse the reductive transfer of several pollutants, and the commonly occurring flavin enzyme cofactor riboflavin, were found to be extremely powerful catalysts, capable of raising the pseudo first-order reaction rate constants by orders of magnitude. Moreover, a large stimulatory effect was found for autoclaved sludge, presumably due to the release of internal electron carriers, e.g. enzyme cofactors like riboflavin, during autoclaving.

    AQDS was successfully applied to improve the continuous reduction of Reactive Red 2 (a reactive azo dye with a triazyl reactive group) in a lab-scale anaerobic bioreactor that was operated under moderate hydraulic loading conditions. Without AQDS, the reactor's dye removal efficiency was very low, which gave rise to severe dye toxicity towards the biological activity. Addition of catalytic concentrations of AQDS to the reactor influent caused an immediate increase of the dye removal efficiency and recovery of the methane production. Eventually, almost complete RR2 colour removal could be reached.

    Though effective AQDS dosage levels are low, continuous dosing has disadvantages with respect to the costs and the discharge of this biologically recalcitrant compound. Therefore, the feasibility of activated carbon (AC), which is known to contain quinone groups at its surface, to act alternatively as an insoluble/immobilised redox mediator was explored. Incorporation of AC in the sludge of lab-scale anaerobic bioreactors that treated Reactive Red 2 in synthetic wastewater containing volatile fatty acid as primary electron donor resulted in enhanced continuous dye reduction as compared to the control reactors without AC. The effect of AC was in large excess of its dye adsorption capacity. In addition, it was shown that bacteria could utilise AC as terminal electron acceptor in the oxidation of acetate. Moreover, AC catalysis of chemical azo dye reduction by sulphide was demonstrated. These results clearly suggest that AC accepts electrons from the microbial oxidation of organic acids and transfers the electrons to azo dyes, thereby accelerating their biological reduction.

    The research presented in this thesis makes clear that the reduction of azo dyes can be optimised by utilising redox mediators, i.e. either by continuous dosing of soluble quinones or by incorporation of AC in the sludge blanket. The potential of using redox mediators is probably not limited to enhancing azo dye reduction but may be extrapolated to other non-specific reductive (bio)transformations, e.g. reduction of halogenated or nitroaromatic compounds. The potential of using redox mediators is furthermore probably not limited to wastewater treatment but may also apply to bioremediation of soils polluted with e.g. polychlorinated solvents or nitroaromatic pesticides.

    Heavy metals extraction from anaerobically digested sludge
    Marchioretto, M.M. ; Bruning, H. ; Loan, N.T.P. ; Rulkens, W.H. - \ 2002
    Water Science and Technology 46 (2002)10. - ISSN 0273-1223 - p. 1 - 8.
    afvalwaterbehandeling - geactiveerd slib - zware metalen - anaërobe behandeling - anaërobe afbraak - extractie - waste water treatment - activated sludge - heavy metals - anaerobic treatment - anaerobic digestion - extraction
    This paper reports on the chemical extraction efficiency in the removal of heavy metals from sludge from an activated-sludge system, which receives as influent both industrial and municipal wastewater. Utilizing a series of chemical extractants in a sequential order comprised the first phase of the research, called sequential chemical extraction (SCE). The work started with the well-known Tessier method followed by Veeken and by Sims and Kline SCE schemes. Afterwards, modified versions of Tessier and Veeken schemes were applied. The second phase, named chemical extraction using pH progressive changes, concerns an alternative to the extraction process. Four acids were tested: nitric, hydrochloric, oxalic and citric and the pH values as well as the time were varied. Some conclusions reveal that although modifying Tessier and Veeken schemes provides more consistent results, SCE is still an imperfect method regarding specificity and selectivity. Besides, it is not advisable to apply one SCE scheme developed for one specific situation to another one, once the accurateness of the method depends on several factors such as sort of material and chemicals, contact time, temperature, etc. The extraction efficiency increases using nitric or hydrochloric acids at low pH values, promoting high extraction efficiency level.
    Quinones as electron acceptors and redox mediators for the anaerobic biotransformation of priority pollutants
    Cervantes-Carrillo, F.J. - \ 2002
    Wageningen University. Promotor(en): G. Lettinga; J.A. Field. - S.l. : S.n. - ISBN 9789058085672 - 162
    anaërobe behandeling - anaërobe afbraak - verontreinigende stoffen - chinonen - humuszuren - redoxreacties - anaerobic treatment - anaerobic digestion - pollutants - quinones - humic acids - redox reactions
    Humus is the most abundant organic fraction in the biosphere. It is composed of a complex structure in which recalcitrant polymers prevail with a residence time lasting decades or even centuries. Despite the recalcitrance of humic substances, they have recently been recognized to play an important role on the anaerobic conversion of organic matter by serving as an electron acceptor for microbial respiration. Quinone moieties are the responsible electron-accepting groups accounting for the microbial reduction of humus. Quinones and humus not only serve as terminal electron acceptors for microbial respiration, but they also function as redox mediators during the transfer of electrons in microbial and chemical reactions. In this dissertation the impact of humus and quinone analogues on the anaerobic biotransformation of ecologically important substrates, as well as priority pollutants, was evaluated.

    Consortia obtained from many different environments including sandy, organic rich, and contaminated sediments, as well as anaerobic and aerobic sludges, showed the capacity for oxidizing a wide variety of ecologically significant substrates, such as lactate and acetate, when the humic model compound, anthraquinone-2,6-disulfonate (AQDS), was provided as a final electron acceptor. AQDS-reducing microorganisms out-competed methanogens for most of the substrates supplied indicating that quinone reduction is a widespread physiological process, which may contribute to important carbon cycling process in many different environments. Quinone and humus reduction was also found in pure cultures of different microorganisms, such as Desulfitobacterium spp. and Methanospirillum hungatei, indicating that the ubiquity of quinone reduction may be due to the wide diversity of microorganisms with the capacity for reducing humic substances. The results also illustrate that phylogenetically distinct microorganisms can channel electrons from anaerobic substrate oxidation via quinone reduction towards the reduction of metal oxides. Quinone respiring microorganisms could also be enriched and immobilized in the microbial community of an anaerobic granular sludge of a upflow anaerobic sludge blanket (UASB) reactor. The feasibility to immobilize quinone-reducing microorganisms can be applied to accelerate the conversion of xenobiotics susceptible to reductive biotransformations such as azo dyes and polychlorinated compounds in continuous bioreactors.

    The long-term goal of this research was to explore the capacity of humus respiring consortia for oxidizing priority pollutants through the reduction of humic substances. Anaerobic granular sludge originated from different wastewater treatment plants were shown to oxidize phenol and p -cresol coupled to the reduction of AQDS. Both phenolic contaminants were converted to methane in the absence of the humic analogue, but addition of AQDS as an alternative electron acceptor diverted the flow of electrons from methanogenesis towards quinone reduction. Priority pollutants, which were not degraded under methanogenic conditions, could also be mineralized by humus-respiring consortia when humic substances were provided as an electron acceptor. Enriched sediments from different origins readily mineralized uniformly labeled [ 13C]toluene to 13CO 2 when humic acids or AQDS were provided as terminal electron acceptors. Negligible recovery of 13CO 2 occurred in the absence of humic substances. Additionally, the electrons in the toluene mineralized were recovered stoichiometrically as reduced humus or AH 2 QDS (reduced form of AQDS).

    Humic substances were also shown to accelerate the transfer of reducing equivalents required for the anaerobic conversion of different pollutants containing electron-withdrawing groups. AQDS supplemented at sub-stoichiometric levels in granular sludge incubations enhanced the rate of conversion of carbon tetrachloride (CT) leading to an increased production of inorganic chloride. Negligible dechlorination occurred in sterile controls with autoclaved sludge and considerably less dechlorination was achieved in active controls lacking AQDS. A humus respiring enrichment culture, composed primarily of a Geobacter sp., derived from the same granular sludge was also shown to dechlorinate CT, yielding similar products as the AQDS-supplemented sludge consortium. Addition of catalytic levels of AQDS to a UASB reactor continuously treating the azo dye, acid orange 7 (AO7), also enhanced the biotransformation of this pollutant to the corresponding aromatic amines. High efficiency (>90 %) of decolorization of AO7 occurred even at a hydraulic residence time of 2 hours with a molar ratio of AQDS/AO7 as low as 1/100, whereas 70 % of color removal occurred in the absence of AQDS under the same hydraulic conditions.

    The evidences provided in this study indicate that humic substances may play an important role on the stabilization of organic matter, as well as on the intrinsic bioremediation of contaminated environments, by serving as a terminal electron acceptor. The application of humic substances for achieving the bioremediation of contaminated aquifers can be considered. Humus and quinones can also be applied in anaerobic reactors to enhance the conversion of priority pollutants containing electron-withdrawing groups.

    The biorotor system for post-treatment of anaerobically treated domestic sewage
    Tawfik, A. - \ 2002
    Wageningen University. Promotor(en): G. Lettinga; F. El-Gohary; A. Klapwijk. - S.l. : S.n. - ISBN 9789058085658 - 140
    anaërobe behandeling - rioolafvalwater - sedimentatie - escherichia coli - anaerobic treatment - sewage effluent - sedimentation - escherichia coli

    This thesis describes the evaluation of the applicability of biorotor system for post-treatment (polishing) of different effluent qualities of an UASB reactor treating raw domestic sewage, with emphasis on the elimination of various COD fractions, ammonia and E.Coli.

    The removal mechanism of E.Coli from UASB effluent using a RBC has been investigated. The results obtained revealed that an adsorption process and sedimentation comprise the most important removal mechanism of E.Coli in the biofilm. Die-off is relatively minor importance as removal mechanism in a RBC system.

    The performance of an anaerobic versus aerobic RBC system treating a high quality UASB reactor effluent was investigated at the same HRT and OLR. The results obtained indicated that the removal efficiency of the COD fractions and of E.Coli fractions found in the aerobic RBC significantly exceeds that of the anaerobic unit. Therefore, the results of our investigations strongly support the use of an aerobic RBC as a post-treatment step of UASB reactor effluents.

    When applying a single and two stage aerobic RBC at the same OLR of 14.5 g COD total .m -2.d -1and at a HRT of 2.5 h., but at different temperatures of 24 and 17 °C respectively, both systems provided the same residual effluent values for COD total (72 mg l -1), for COD suspended (16 mg l -1), for COD colloidal (5 mg l -1) and for COD soluble (51 mg l -1). Moreover, also the removal efficiency of E.Coli was almost the same, viz. amounting to 94 %. However, the ammonia removal in the single stage RBC amounted to 50 % of which 71 % was nitrified, compared to only 23 % in the two-stage system. This better performance can be attributed to the higher temperature of the wastewater during the operation of the single stage RBC system. In view of these results, we recommend to use a single stage RBC system for COD removal and for a partial nitrification and E.Coli removal at OLR of 14.5 g COD total .m -2.d -1and at HRT of 2.5 h for post-treatment of a high quality UASB reactor effluent.

    We investigated the use of anoxic reactor followed by a segmental two stage aerobic RBC for nitrogen removal from the nitrified effluent. The results obtained reveal that the introduction of an anoxic reactor as a 1 ststage combined with recirculation of the nitrified effluent of the 2 ndstage RBC is accompanied with a conversion of nitrate into ammonia, at least in case the content of COD biod. in the UASB effluent is low. Therefore, the introduction of a separate anoxic reactor for denitrification as final post-treatment step can not be recommended in such a situation.

    In one of the experiments the UASB reactor was operated at two different operational temperatures viz. of 30 and 11°C resulting in quite different COD biod. concentrations in the UASB effluent. For the post-treatment of this highly different effluent a single stage RBC was operated at a constant HRT of 1.25 h., consequently at COD biod. loading rates of 17.7 and 36.8 g m -2. d -1. The results clearly show that the residual values of COD fractions and E.Coli are significantly lower at the lower imposed COD biod. loading rate of 17.7g COD biod. m -2. d -1. We also compared the efficiency of the two-stage RBC system for this highly different UASB effluent, viz. once again at the same HRT (2.5 h) and at COD biod. loading rate of 9 and 18 g m -2. d -1. The results reveal that with the two-stage RBC system the residual values of distinguished COD fractions in the final effluent were almost the same, but the residual value of E.Coli in the final effluent amounted to 3.4 x 10 5at the higher COD biod. loading rate and to 7.6 x 10 4/100 ml at the lower one. Moreover, the calculated nitrification rate in the 2 ndstage of two stage RBC system dropped from 1.56 to 1.1 g NO 3 -N.m -2.d -1with an increase the COD biod. loading rate from 11.3 to 16 g m -2.d -1. The results clearly demonstrate that the introduction of a well performing UASB reactor not only improves the nitrification rate but also the E.Coli removal in the post-treatment system.

    We compared the performance of the single with that of a two-stage RBC for the treatment of poor quality UASB reactor effluent. The results obtained showed that the COD fractions and the E.Coli content in the final effluent of a two stage were lower than in the effluent of the single stage RBC. Moreover, The calculated nitrification rate in the single stage was much lower compared with the two stages RBC. Based on these results we recommend a two stage RBC system for post-treatment of poor quality UASB reactor effluent. The two-stage system was operated at different HRT's and OLR's in order to assess better design criteria for the system. The removal efficiencies for the various COD fractions decreased only slightly when decreasing the HRT from 10 to 2.5 h., and increasing the OLR from 6.45 to 24 g COD total m -2.d -1. However, the overall nitrification efficiency and E.Coli were negatively affected when increasing the loading conditions in the range investigated. The results found for E.Coli removal revealed that the major part of suspended E.Coli (>4.4 µm) was eliminated by sedimentation or by adsorption in the biofilm of the 1 ststage (99.66 %). However, E.Coli present in the colloidal fraction (< 4.4 - > 0.45 µm) was eliminated in the 2 ndstage of two stage RBC (99.78 %). Based on these results we recommend for the treatment of a poor UASB effluent quality the use of two stages RBC system for the removal of COD fractions and ammonia and for a partial removal of E.Coli at HRT of 10 h and OLR of 6.45 g COD total .m -2.d -1.

    The effluent of two stages still cannot be used for unrestricted irrigation purposes, at least according to the standards provided by the WHO with respect to the E.Coli content. Therefore, in order to meet these (very stringent) standards, we investigated the use of a three stage RBC-system for post-treatment of an effluent from a rather poorly performing UASB reactor. This three stage RBC was first operated at a HRT of 3.0 h. Under these conditions the E.Coli count in the final effluent was still too high. However, when applying an HRT of 10 h., the E.Coli content complied almost the WHO standards for unrestricted irrigation purposes. Therefore, when such high removal efficiency for E.Coli really would be required, the best solution is to use three independent stages at HRT of 10 h., which then obviously implies very significantly investment and operational costs.

    Treatment of anaerobically pre-treated domestic sewage by a rotating biological contactor
    Tawfik, A. ; Klapwijk, A. ; el-Gohary, F. ; Lettinga, G. - \ 2002
    Water Research 36 (2002)1. - ISSN 0043-1354 - p. 147 - 155.
    afvalwaterbehandeling - nitrificatie - rioolafvalwater - anaërobe behandeling - zuurstof - retentie - escherichia coli - chemisch zuurstofverbruik - biologische behandeling - waste water treatment - nitrification - sewage effluent - anaerobic treatment - oxygen - retention - escherichia coli - chemical oxygen demand - biological treatment
    The performance of a rotating biological contactor (RBC) for the post-treatment of the effluent of an up-flow anaerobic sludge blanket (UASB) was the subject of this study. Different hydraulic and organic loading rates have been investigated. The removal efficiencies of CODtotal, CODsuspended, CODcolloidal and CODsoluble increased at a higher hydraulic retention time (HRT) and a lower influent organic loading rate.The results obtained indicated that a two-stage RBC reactor at an HRT of 10h and an organic loading rate of 6.4g CODm-2d-1 represents an effective post-treatment process. Most CODsuspended and CODcolloidal were removed in the first stage while nitrification proceeded in the second stage.The overall nitrification efficiency was 92% at an ammonia loading rate of 1.1gm-2d-1. Total E. coli removal at HRTs of 10, 5 and 2.5h were 99.5%, 99.0% and 89.0%, respectively. The major part of suspended E. coli (>4.4μm) was removed by sedimentation or by adsorption in the biofilm of the first stage of RBC (99.66%). However, E. coli in the colloidal fraction (<4.4 to >0.45μm) was eliminated in the second stage of RBC (99.78%).A comparison of the performance of a one-stage versus two-stage RBC system, operated at the same total loading rate, revealed an improvement in the effluent quality of the two-stage effluent as compared to the one-stage effluent.The two stages RBC were used to examine the effect of hydraulic shock loads on reactor performance in terms of COD, nitrification and E. coli removal. Copyright
    Ontbinding, lucht voor leven
    Lettinga, G. - \ 2001
    Wageningen : Wageningen Universiteit - 55
    anaërobe behandeling - anaërobe afbraak - afvalwaterbehandeling - openbare redes - anaerobic treatment - anaerobic digestion - waste water treatment - public speeches
    Ozonation followed by coagulation/flocculation and flotation as post-treatment of the effluent from an anaerobic baffled reactor treating domestic wastewater.
    Marchioretto, M.M. ; Reali, M.A.P. - \ 2001
    Water Science and Technology 43 (2001)8. - ISSN 0273-1223 - p. 99 - 106.
    afvalwaterbehandeling - rioolafvalwater - anaërobe behandeling - ozon - coagulatie - uitvlokking - flotatie - waste water treatment - sewage effluent - anaerobic treatment - ozone - coagulation - flocculation - flotation
    Anaerobic digestion of domestic sewage al low temperature
    Elmitwalli, T.A. ; Zeeman, G. ; Lettinga, G. - \ 2001
    Water Science and Technology 44 (2001)4. - ISSN 0273-1223 - p. 33 - 40.
    afvalwaterbehandeling - anaërobe behandeling - rioolwater - anaërobe afbraak - polyurethanen - schuim - temperatuur - waste water treatment - anaerobic treatment - sewage - anaerobic digestion - polyurethanes - foams - temperature
    The results of research concerning the feasibility of anaerobic treatment of domestic sewage at low temperature are summarized in this article. The batch tests demonstrated a high biodegradability of domestic sewage at 20°C (74Ž Both batch and continuous experiments for the treatment of domestic sewage showed that the removal of SS prior to anaerobic treatment of domestic sewage not only provides a stable reactor performance but also improves the removal of both colloidal (CODcol) and dissolved COD (CODdis). The results of the pre-treatment of domestic sewage in an anaerobic filter (AF) and an anaerobic hybrid (AH) reactor showed that the AF reactor is an efficient process for the removal of suspended COD (CODss), viz. 82°at an HRT of 4 h and 13°C. The novel AF reactor consists of vertical sheets of reticulated polyurethane foam with knobs, where the biomass was only in attached form. For the treatment of pre-settled sewage at 13°C, the AH reactor, with granular sludge, showed a higher total COD (CODt) removal than the UASB reactor as a result of higher CODcol removal. Therefore, the performance of a two-step system, AF AH (with granular sludge) reactor, was investigated with different HRTs at 13°C. For optimization of CODss and CODdis an HRT of 4 4 h is needed, while for optimization of CODcol removal an HRT of 4 8 h is required. A CODt removal of 71 as achieved with 60␌onversion to methane from the removed CODt when the AF AH system was operated at an HRT of 4 8 h at 13°C.
    Behandeling van stedelijk afvalwater met een twee-slibsoortensysteem
    Temmink, B.G. ; Klapwijk, A. ; Rulkens, W.H. - \ 2001
    Stowa - ISBN 9789057731532 - 37
    rioolwater - afvalwaterbehandeling - anaërobe behandeling - anoxie - fosfor - verwijdering - bioremediëring - sewage - waste water treatment - anaerobic treatment - anoxia - phosphorus - removal - bioremediation
    Biodegradability and change of physical characteristics of particles during anaerobic digestion of domestic sewage
    Elmitwalli, T.A. ; Soellner, J. ; Keizer, A. de; Bruning, H. ; Zeeman, G. ; Lettinga, G. - \ 2001
    Water Research 35 (2001). - ISSN 0043-1354 - p. 1311 - 1317.
    rioolwater - afvalwaterbehandeling - anaërobe behandeling - biodegradatie - oppervlaktespanningsverlagende stoffen - sewage - waste water treatment - anaerobic treatment - biodegradation - surfactants
    The potential of anaerobic bacteria to degrade chlorinated compounds
    Eekert, M.H.A. van; Schraa, G. - \ 2001
    In: Anaerobic digestion for sustainable development : papers of the farewell seminar of prof. dr. ir. Gatze Lettinga, March 29 and 30, 2001, Wageningen, The Netherlands Environmental Protection and Resource Conservation Foundation (EP&RC) - p. 51 - 59.
    grondwater - afvalwater - waterverontreiniging - afvalwaterbehandeling - anaërobe behandeling - gechloreerde koolwaterstoffen - degradatie - groundwater - waste water - water pollution - waste water treatment - anaerobic treatment - chlorinated hydrocarbons - degradation
    Sustainable development in pollution control and the role of anaerobic treatment.
    Lettinga, G. ; Lier, J.B. van; Buuren, J.C.L. van; Zeeman, G. - \ 2001
    Water Science and Technology 44 (2001)6. - ISSN 0273-1223 - p. 181 - 188.
    afvalwaterbehandeling - anaërobe behandeling - hergebruik van water - verontreinigingsbeheersing - milieubescherming - waste water treatment - anaerobic treatment - water reuse - pollution control - environmental protection
    The increasing scarcity of clean water sets the need for appropriate management of available water resources. Particularly regions suffering from a lack of water urgently need integrated environmental protection and resource conservation (EP and RC) technologies in order to enable effective management of the available water resources. EP and RC-concepts focus on pollution prevention and on a maximum of consumptive use of energy, chemicals, and water in pollution prevention and on a minimum of consumptive une of energy, chemicals, and water in pollution abatement and a maximum of re-use of treated wastewater, by-products and residues produced in the treatment of waste and wastewater. Consequently, by implementing these concepts, waste(water)s like sewage and industrial effluents become an important source of water, fertilisers, soil conditioners and (frequently) energy instead of a social threat. In addition, a bridge is made between environmental protection and agriculture practice, stimulating (urban) agriculture in the neighbourhood of large cities. Anaerobic treatment is considered as the core technology for mineralising organic compounds in waste(water) streams. Additional technologies are required to comply with the reuse criteria. Some examples of possible EP and RC concepts, using the anaerobic treatment technology for the reclamation of domestic sewage are discussed.
    Feasibility of the on-site treatment of sewage and swill in large buildings
    Zeeman, G. ; Sanders, W.T.M. ; Lettinga, G. - \ 2000
    Water Science and Technology (2000)1. - ISSN 0273-1223 - p. 9 - 16.
    rioolafvalwater - afvalwaterbehandeling - anaërobe behandeling - afval - gebouwen - ziekenhuizen - gesloten systemen - sewage effluent - waste water treatment - anaerobic treatment - wastes - buildings - hospitals - closed systems
    Impact of location of CaCO3 precipitation on the development of intact anaerobic sludge
    Langerak, E.P.A. van; Ramaekers, H. ; Wiechers, J. ; Veeken, A.H.M. ; Hamelers, H.V.M. ; Lettinga, G. - \ 2000
    Water Research 34 (2000)2. - ISSN 0043-1354 - p. 437 - 446.
    afvalwaterbehandeling - anaërobe behandeling - calciumcarbonaat - chemische precipitatie - biofilms - modellen - slib - waste water treatment - anaerobic treatment - calcium carbonate - chemical precipitation - biofilms - models - sludges
    The development of intact anaerobic granular sludge was studied in UASB reactors under varying conditions of CaCO3 precipitation and biomass yield. Varying precipitating quantities were obtained using different calcium concentrations in the influent and different biomass yields were obtained by feeding with completely or partly acidified substrate. Four reactors were operated at a constant organic loading rate of 13g COD l-1 d-1. Treatment of completely acidified waste water with high calcium concentrations (780-1560 mgCa2 l-1) resulted in the rapid formation of dense granules with a high ash content of which the specific methanogenic activity rapidly dropped and which easily agglomerated, leading to serious cementation of the sludge bed. At a lower influent calcium concentration (390 mgCa2 l-1), treatment of completely acidified waste water resulted in precipitation on reactor compartments, while precipitation within the aggregates did hardly take place. The presence of a fraction of non-acidified substrate retarded cementation of the sludge bed and resulted in development of sludge with a high ash content and a satisfactory quality. The biofilm model developed was shown to provide a clear, qualitative insight in the factors that affect the location of precipitation, and thereby the quality of high ash content sludge. Moreover, it explains the differences observed in the location of precipitation during the experiments. A low Ca/Na ratio, a small granule diameter and a high crystallization rate constant (=low CaCO3 growth inhibition) were found to stimulate precipitation in the bulk solution, and are considered to be favourable parameters for the development of sludge with a high ash content and a good quality.
    Anaerobic hydrolysis kinetics of particulate substrates
    Sanders, W.T.M. ; Geerink, M. ; Zeeman, G. ; Lettinga, G. - \ 2000
    Water Science and Technology (2000)3. - ISSN 0273-1223 - p. 17 - 24.
    afvalwaterbehandeling - anaërobe behandeling - kinetica - substraten - zetmeel - hydrolyse - waste water treatment - anaerobic treatment - kinetics - substrates - starch - hydrolysis
    Kinetics of syntrophic cultures: A theoretical treatise on butyrate fermentation
    Kleerebezem, R. ; Stams, A.J.M. - \ 2000
    Biotechnology and Bioengineering 67 (2000)5. - ISSN 0006-3592 - p. 529 - 543.
    afvalwaterbehandeling - kinetica - thermodynamica - anaërobe behandeling - butyraten - fermentatie - waste water treatment - kinetics - thermodynamics - anaerobic treatment - butyrates - fermentation
    Numerous microbial conversions in methanogenic environments proceed at (Gibbs) free energy changes close to thermodynamic equilibrium. In this paper we attempt to describe the consequences of this thermodynamic boundary condition on the kinetics of anaerobic conversions in methanogenic environments. The anaerobic fermentation of butyrate is used as an example. Based on a simple metabolic network stoichiometry, the free energy change based balances in the cell, and the flux of substrates and products in the catabolic and anabolic reactions are coupled. In butyrate oxidation, a mechanism of ATP-dependent reversed electron transfer has been proposed to drive the unfavorable oxidation of butyryl-CoA to crotonyl-CoA. A major assumption in our model is that ATP-consumption and electron translocation across the cytoplasmic membrane do not proceed according to a fixed stoichiometry, but depend on the cellular concentration ratio of ATP and ADP. The energetic and kinetic impact of product inhibition by acetate and hydrogen are described. A major consequence of the derived model is that Monod-based kinetic description of this type of conversions is not feasible, because substrate conversion and biomass growth are proposed to be uncoupled. It furthermore suggests that the specific substrate conversion rate cannot be described as a single function of the driving force of the catabolic reaction but depends on the actual substrate and product concentrations. By using nonfixed stoichiometries for the membrane associated processes, the required flexibility of anaerobic bacteria to adapt to varying environmental conditions can be described.
    The role of sludge retention time in the hydrolysis and acidification of lipids, carbohydrates and proteins during digestion of primary sludge in CSTR systems
    Miron, Y. ; Zeeman, G. ; Lier, J.B. van; Lettinga, G. - \ 2000
    Water Research 34 (2000)5. - ISSN 0043-1354 - p. 1705 - 1713.
    afvalwaterbehandeling - rioolslib - anaërobe behandeling - koolhydraten - lipiden - eiwitten - verzuring - hydrolyse - waste water treatment - sewage sludge - anaerobic treatment - carbohydrates - lipids - proteins - acidification - hydrolysis
    CSTR systems: completely stirred tank reactor systems
    Thermophilic sulfate and sulfite reduction with methanol in a high rate anaerobic reactor
    Weijma, J. ; Haerkens, J. ; Stams, A.J.M. ; Hulshoff Pol, L.W. ; Lettinga, G. - \ 2000
    Water Science and Technology 42 (2000). - ISSN 0273-1223 - p. 251 - 258.
    afvalwaterbehandeling - industrieel afval - ontzwaveling - methanol - anaërobe behandeling - waste water treatment - industrial wastes - desulfurization - methanol - anaerobic treatment
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