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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    Behavioural response of silver eel to effluent plumes: Telemetry experiments
    Winter, H.V. ; Keeken, O.A. van; Foekema, E.M. ; Kleissen, F. ; Friocourt, Y. ; Beare, D.J. - \ 2011
    IJmuiden : IMARES (Report / IMARES Wageningen UR C081/11) - 57
    palingen - prikvissen - afvoerwater - rioolafvalwater - diergedrag - vismigratie - telemetrie - eels - lampreys - effluents - sewage effluent - animal behaviour - fish migration - telemetry
    Fish migration may be hampered by a range of physical barriers. That non-physical barriers such as sudden changes in water quality may also serve as barriers is often stated, but only very few studies address this issue. This study focusses on linking the behavioural response of silver eel and river lamprey when encountering a waste water plume (effluent) in field situations. Individual fish movements were tracked by means of acoustic telemetry in 2D (in 2009) and in 3D (in 2010) at a location surrounding a waste water outlet in the Eems-canal near Groningen. Plume dynamics were modelled and calibrated by Deltares and used to directly link to individual movement patterns of fish. In both years, 20 silver eels (downstream migration) were tagged and in 2009 also 13 rvier lamprey (upstram migration) were tagged. In total, 37 out of 40 silver eels entered the 2D – 3D study site. Of these, 57 % showed avoidance behaviour when encountering the plume, 43 % were indifferent to the plume and no attraction to the plume was observed. Avoidance behaviour varied from moving away from the plume but continuing the migration, to returning and not be detected again, thereby possibly ceasing their migration (3 out of 37). This indicates that waste water plumes may serve as non-physical barriers to migrating silver eel. Given the very dynamic nature of the plume in Groningen, even if waste water plumes serve as non-physical barriers for some of the migrating eels, numerous migratory windows are available in time and in water depths, when the plume is minimal or limited to one shore. Therefore it is estimated that the barrier effect of waste water plumes might be small, although delays in migration are likely to occur. Our findings may be used for management purposes. The occurrence of a behavioural avoidance response of approximately half of the eels opens up the possibility to manipulate plumes in order to ‘steer’ silver eels to a preferred direction, e.g. away from potential hazardous locations.
    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
    Resource recovery from black water
    Graaff, M.S. de - \ 2010
    Wageningen University. Promotor(en): Cees Buisman, co-promotor(en): Grietje Zeeman; Hardy Temmink. - [S.l. : S.n. - ISBN 9789085855484 - 192
    rioolafvalwater - nieuwe sanitatie - anaërobe afbraak - bio-energie - nitrificatie - verzamelen - riolering - urine - sewage effluent - new sanitation - anaerobic digestion - bioenergy - nitrification - collection - sewerage - urine
    New sanitation systems based on separation at source offer a large potential for resource recovery from wastewater, e.g. energy and nutrients from black water and irrigation water from grey water. This review focuses on the components in source separated black water. The treatment options for the key components are reviewed, focusing on recovery of organic compounds, nitrogen and phosphorus and removal of hormones, pharmaceutical residues and pathogens. A feasible treatment system for black water (faeces and urine), collected with vacuum toilets, would consist of anaerobic treatment followed by struvite precipitation for phosphorus recovery and autotrophic nitrogen removal. By applying these techniques, it is possible to produce 56 MJ/p/y of electricity, representing 40% of the energy that now is required for conventional WWTPs. Furthermore, the production of global artificial phosphorus fertilizer can be reduced by maximum 21%. As an alternative a higher degree of separation could be applied by separating the urine from the faeces, but this only would be feasible if the urine can be directly reused as a fertilizer. The issue of hormones, pharmaceuticals and pathogens in wastewater and their entry into the environment requires more research to determine to which extent additional treatment is necessary. Finally, the scope of this thesis is explained and the research questions which were addressed are presented.
    SPME as a tool in WEA - CONCAWE Contribution to OSPAR Demonstration Project 2005 - 2006
    Leslie, H.A. - \ 2006
    IJmuiden : RIVO (Report / RIVO C020/06) - 187
    extractie - rioolafvalwater - bioaccumulatie - bioconcentratie - kwaliteitscontroles - extraction - sewage effluent - bioaccumulation - bioconcentration - quality controls
    This document represents a compilation of various data and deliverables from the study programme. An executive summary is followed by the presentation of data generated in an interlaboratory study of effluents assessed using both EGOM-LLE and biomimetic SPME methods.
    Oestrogene effecten in vissen in regionale wateren nabij rwzi's
    Rijs, G. ; Gerritsen, A. ; Lahr, J. ; Bulder, A. - \ 2004
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 37 (2004)5. - ISSN 0166-8439 - p. 15 - 18.
    vissen - abramis brama - oestrogenen - hormonen - aquatisch milieu - oppervlaktewater - waterverontreiniging - rioolafvalwater - nederland - aquatische ecosystemen - zuiveringsinstallaties - fishes - abramis brama - oestrogens - hormones - aquatic environment - surface water - water pollution - sewage effluent - netherlands - aquatic ecosystems - purification plants
    Het Landelijk Onderzoek oEstrogene Stoffen (LOES) heeft laten zien dat hormoonontregelende stoffen bijna overal in lage concentraties in het Nederlandse watermilieu voorkomen. Vissen in regionale wateren blijken evenwel een groter risico te lopen op nadelige effecten, zoals vervrouwelijking, dan de vissen in de wat grotere wateren. De oorzaak hiervoor lijkt te liggen in het feit dat wanneer regionale wateren onder directe invloed van lozingen met hormoonontregelende stoffen staan in kleinere wateren relatief weinig verdunning optreedt. Eén van de emissiebronnen die uitgebreid onderzocht is, is het effluent van een rioolwaterzuivering
    Verwijdering van hormoonverstorende stoffen in rwzi's
    Loeffen, P. ; Lahr, J. ; Derksen, A. ; Uijterlinde, C. ; Roeleveld, P. - \ 2004
    H2O : tijdschrift voor watervoorziening en afvalwaterbehandeling 37 (2004)5. - ISSN 0166-8439 - p. 19 - 21.
    afvalwaterbehandeling - rioolafvalwater - hormonen - oestrogenen - waterzuivering - oppervlaktewater - waterverontreiniging - zuiveringsinstallaties - hormoonverstoorders - waste water treatment - sewage effluent - hormones - oestrogens - water treatment - surface water - water pollution - purification plants - endocrine disruptors
    Door de STOWA is eind vorig jaar een literatuurstudie naar de verwijdering van hormoonverstorende stoffen (ook wel endocrine disrupting chemicals of EDC's genoemd) in rioolwaterzuiveringsinstallaties verricht. Hieruit blijkt dat, ondanks een redelijke verwijdering in de rwzi, de concentraties van bepaalde EDC's in het effluent nog steeds kunnen leiden tot biologische effecten. De grootste risico's geven de oestrogene hormonen 17a-ethinyloestradiol ('de pil'), 17beta-oestradiol en oestron en de industriële detergenten nonylfenol en nonylfenolethoxylaten. Het is onduidelijk hoe de huidige rioolwaterzuiveringsinstallaties geoptimaliseerd kunnen worden om hormoonverstorende stoffen te verwijderen. Geavanceerde technieken lijken de beste resultaten op te leveren
    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 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.
    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.
    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.
    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.
    Treatment of anaerobically treated domestic wastewater using rotating biological contactor
    Tawfik, A. ; Klapwijk, A. ; El-Gohary, F. ; Lettinga, G. - \ 2002
    Water Science and Technology 45 (2002)10. - ISSN 0273-1223 - p. 371 - 176.
    afvalwaterbehandeling - fecale coliformen - rioolafvalwater - ronddraaiende biologische contactbedden - biologische behandeling - waste water treatment - faecal coliforms - sewage effluent - rotating biological contactors - biological treatment
    A small-scale pilot plant consisting of a three-stage RBC has been investigated for the removal of E. coli, COD fractions and ammonia from the effluent of an UASB reactor treating domestic wastewater. The results obtained reveal that a three-stage system operated at a HRT of 3.0 h represents an effective posttreatment process. The remaining COD in the final effluent was only 51 ( /- 7) mgl(-1). Ammonia concentration was reduced by 67 ( /- 7.6) ÐThe overall E. coli reduction was 1.39 log10 at an influent count of 6.5 log10 corresponding to an overall removal efficiency of 95.8 ( /- 4.7) ÐHowever, according to prevailing standards, residual E. coli counts are still high for unrestricted reuse for irrigation purposes. When the system was operated at a HRT of 10 h, overall E. coli removal and ammonia reduction were 99.9 ( /- 0.05)nd 92 ( /- 6.5) ␛espectively. At a HRT of 10 h, recirculation of the 3rd stage effluent to the 1st stage reduced the residual of E. coli in the final effluent from 2 x 10(3) to 9.8 x 10(2)/100ml. Moreover, the recirculation of nitrified effluent from the 3rd stage to the 1st stage increased ammonia removal in the stage 1 from 23 to 43ÐThis relatively high ammonia removal likely can be attributed to the supply of nitrifiers from 3rd stage to the 1st one.
    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.
    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%.

    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
    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
    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
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