Conversion of polyhydroxybutyrate (PHB) to methyl crotonate for the production of biobased monomers
Spekreijse, J. ; Notre, J.E.L. Le; Sanders, J.P.M. ; Scott, E.L. - \ 2015
Journal of Applied Polymer Science 132 (2015)35. - ISSN 0021-8995 - 8 p.
gas-chromatographic analysis - thermal-degradation - poly(-(d)-beta-hydroxybutyric acid) - quantitative-analysis - abiotic hydrolysis - activated-sludge - molecular-weight - polyhydroxyalkanoates - poly(3-hydroxybutyrate) - alkaline
Within the concept of the replacement of fossil with biobased resources, bacterial polyhydroxybutyrate (PHB) can be obtained from volatile fatt y acids (VFAs) from agro-food waste streams and used as an intermediate toward attractive chemicals. Here we address a crucial step in this process, the conversion of PHB to methyl crotonate (MC), which can be converted via cross- metathesis w ith ethylene to methyl acrylate and propylene, two important monomers for the plastics industry. The conversion of PHB to MC proceeds via a thermolysis of PHB to crotonic acid (CA), followed by an esterification to MC. At pressures below 18 bar, the thermolysis of PHB to CA is the rate-determining step, where above 18 bar, the esterification of CA to MC becomes rate lim- iting. At 2008C and 18 bar, a full conversion and 60% selectiv ity to MC is obtained. This conversion circumvents processing and application issues of PHB as a polymer and allows PHB to be used as an intermediate to produce biobased chemicals.
Characterization of the bacterial community involved in the bioflocculation process of wastewater organic matter in high loaded MBRs
Faust, L. ; Szendy, M. ; Plugge, C.M. ; Brink, P.F. van den; Temmink, H. ; Rijnaarts, H.H.M. - \ 2015
Applied Microbiology and Biotechnology 99 (2015)12. - ISSN 0175-7598 - p. 5327 - 5337.
solids retention time - 16s ribosomal-rna - gradient gel-electrophoresis - improved energy recovery - in-situ hybridization - activated-sludge - microbial community - membrane bioreactor - identification - stability
High-loaded membrane bioreactors (HL-MBRs), i.e., bioreactors equipped with a membrane for biomass retention and operated at extremely short sludge and hydraulic retention times, can concentrate sewage organic matter to facilitate subsequent energy and chemical recovery from these organics. Bioflocculation, accomplished by microorganisms that produce extracellular polymers, is a very important mechanism in these reactors. Bacterial diversity of the sludge and supernatant fraction of HL-MBRs operated at very short sludge retention times (0.125, 0.5, and 1 day) were determined using a PCR-denaturing gradient gel electrophoresis (DGGE) and clone library approach and compared to the diversity in sewage. Already at a sludge retention time (SRT) of 0.125 day, a distinct bacterial community developed compared to the community in sewage. Bioflocculation, however, was low and the majority of the bacteria, especially Arcobacter, were present in the supernatant fraction. Upon increasing SRT from 0.125 to 1 day, a much stronger bioflocculation was accompanied by an increased abundance of Bacteroidetes in the (solid) sludge fraction: 27.5 % at an SRT of 0.5 day and 46.4 % at an SRT of 1 day. Furthermore, cluster analysis of DGGE profiles revealed that the bacterial community structure in the sludge was different from that in the supernatant. To localize specific bacterial classes in the sludge flocs, fluorescence in situ hybridization (FISH) was carried out with three different bacterial probes. This showed that Betaproteobacteria formed clusters in the sludge flocs whereas Alphaproteobacteria and Gammaproteobacteria were mainly present as single cells
Effects of diet composition and ultrasound treatment on particle size distribution and carbon bioavailability in feces of rainbow trout
Meriac, A. ; Tilburg, T. van; Eding, E.H. ; Kamstra, A. ; Schrama, J.W. ; Verreth, J.A.J. - \ 2015
Aquacultural Engineering 65 (2015). - ISSN 0144-8609 - p. 10 - 16.
recirculating aquaculture systems - activated-sludge - anaerobic-digestion - waste-water - feed - fish - denitrification - digestibility - pretreatment - sonication
The effect of a high and low non-starch polysaccharide diet (HNSP and LNSP diet) and ultrasound treatment on particle size distribution and carbon bioavailability in fecal waste of rainbow trout (Oncorynchus mykiss) was studied. Feces were collected from four flow-through fish tanks, two tanks fed the HNSP diet and two the LNSP diet. The collected feces were sonicated (disintegrated) in duplicate with high-intensity (0.6 W/ml), low-frequency (f = 20 Hz) ultrasound at five different energy levels (0.6 W/ml for 0, 0.25, 1, 4, and 16 min). The particle size distribution of the treated feces samples was measured by wet sieving (1000, 500, 200, 100, 63, 36, 1.2 µm screen size) and total suspended solids (TSS) measurement. Carbon bioavailability in sonicated fecal waste samples was determined with oxygen uptake rate (OUR) tests. The results showed that: (1) feces from the HNSP diet contained significant more particulate material and bigger particles; (2) carbon bioavailability was almost three times higher in untreated LNSP feces when compared with HNSP feces; (3) almost 50% of HNSP feces could have been recovered on a microscreen of 36 µm after wet sieving, whereas it was only 10% for LNSP feces; (4) the production of small particles (1.2–36 µm), which could pass a drum filter screen and potentially accumulate in RAS, was approximately 50 g/kg feed, showing no significant differences between diets; (5) sonication increased fecal dry matter below 36 µm (p = 0.015), but it had no significant effect on the median particle size; (6) sonication increased carbon bioavailability with 7–10% for the HNSP feces (p = 0.037); (7) fecal particles withstood up to 16 min sonication at an intensity of 0.6 W/ml and a frequency of 20 Hz corresponding to specific energy input of 20,000 kJ/kg DM without major changes in particle size distribution. The results of this study indicate that the applied ultrasound treatment of fecal waste is not an effective method to increase short-term carbon bioavailability.
Impacts of NF concentrate recirculation on membrane performance in an integrated MBR and NF membrane process for wastewater treatment
Kappel, C. ; Kemperman, A.J.B. ; Temmink, B.G. ; Zwijnenburg, A. ; Rijnaarts, H. ; Nijmeijer, K. - \ 2014
Journal of Membrane Science 453 (2014). - ISSN 0376-7388 - p. 359 - 368.
natural organic-matter - nanofiltration membranes - activated-sludge - treatment plants - heavy-metals - bioreactor - retention - acids
As water shortages are increasing, the need for sustainable water treatment and the reuse of water is essential. Water reuse from wastewater can be accomplished in a membrane bioreactor (MBR) in the secondary activated sludge stage of a wastewater treatment plant. To remove viruses, dissolved organics and inorganics still present in the MBR permeate, nanofiltration (NF) can be applied. Nevertheless, the major drawback of nanofiltration membranes is the production of a concentrate stream that cannot be discharged to the environment. In this research we investigate the concept of a combined MBR and NF system with NF concentrate recirculation back to the MBR to produce reusable water in a sustainable way. Long-term continuous operation (1 year) shows that the NF permeate quality is riot impacted by the recirculation. Fouling on the NF membrane is mostly the result of inorganics, while organics (e.g. humic acids) do not have a major impact on NF fouling. In fact, the flux of the NF was enhanced by the presence of humic acids due to recirculation. However, the MBR showed increased fouling and consequently more frequent membrane cleaning. The results presented show that the continuous production of reusable water from wastewater in a combined MBR and NO process with NO concentrate recirculation can be successful. (C) 2013 Elsevier B.V. All rights reserved
Microbial community dynamics in a submerged fixed bed bioreactor during biological treatment of saline urban wastewater
Cortés-Lorenzo, C. ; Sipkema, D. ; Rodríguez-Díaz, M. ; Fuentes, S. ; Juárez-Jiménez, B. ; Rodelas, B. ; Smidt, H. ; González-López, J. - \ 2014
Ecological Engineering 71 (2014). - ISSN 0925-8574 - p. 126 - 132.
activated-sludge - treatment plants - bacterial diversity - sewage-treatment - biofilm reactor - gradient - denitrification - sea
The influence of salt (NaCl) on bacterial and archaeal communities in a submerged fixed bed bioreactor system for the treatment of urban wastewater was determined by DGGE and 454 pyrosequencing of PCR-amplified 16S ribosomal RNA gene fragments. Cluster analysis of DGGE fingerprints showed significant differences in the community structure dependent on the salt concentration in the influent. Proteobacteria was found to be the dominant bacterial phylum in all experiments, with a-Proteobacteria being the main order at low salinity and ¿-Proteobacteria the dominant order at high salinity. Euryarchaeota was the main archaeal phylum in all experiments, with all microorganisms corresponding to methanogenic archaea. Whereas bacterial a-diversity decreased as salinity increased, archaeal a-diversity increased with higher NaCl concentrations.
Nitrous oxide (N2O) emissions from biotrickling filters used for ammonia removal at livestock facilities
Melse, R.W. ; Mosquera Losada, J. - \ 2014
Water Science and Technology 69 (2014)5. - ISSN 0273-1223 - p. 994 - 1003.
activated-sludge - liquid fraction - water-treatment - nitric-oxide - air - nitrification - operations - manure
Recently several manufacturers of nitrifying biotrickling filters for ammonia (NH3) removal at animal houses have started to add a denitrification step to the installation, aiming to reduce the amount of discharge water by conversion of NH3 to nitrogen gas (N2). The aim of this research was to quantify the possible formation of nitrous oxide (N2O), which is a potent greenhouse gas, in three of these farm-scale installations. Furthermore, the removal efficiency of NH3 and odor was determined. All installations were successful in reducing the amount of discharge water. The average NH3 removal efficiency for the three locations was 85, 71 and 86%, respectively. However, a significant part of the NH3 removed from the inlet air was not converted to N2 but to N2O, which is a potent greenhouse gas. The part of the inlet NH3-N that was converted to N2O-N amounted to 17, 66 and 24%, respectively. The high N2O production might have been caused by a too low scarcity of biodegradable carbon/N ratio for complete denitrification. The average odor removal efficiency was 21, 32 and 48%, respectively. Further research is necessary to explore how process conditions can be adjusted and controlled in order to reduce the production and emission of N2O from these types of systems.
Balancing the organic load and light supply in symbiotic microalgal–bacterial biofilm reactors treating synthetic municipal wastewater
Boelee, N.C. ; Temmink, B.G. ; Janssen, M. ; Buisman, C.J.N. ; Wijffels, R.H. - \ 2014
Ecological Engineering 64 (2014). - ISSN 0925-8574 - p. 213 - 221.
afvalwaterbehandeling - biofilms - symbiose - algen - bacteriën - heterotrofe micro-organismen - fotosynthese - acetaten - stikstof - fosfor - nitrificatie - denitrificatie - biologische waterzuiveringsinstallaties - biobased economy - waste water treatment - biofilms - symbiosis - algae - bacteria - heterotrophic microorganisms - photosynthesis - acetates - nitrogen - phosphorus - nitrification - denitrification - biological water treatment plants - biobased economy - activated-sludge - nutrient removal - growth - phytoplankton - fluorescence - enhancement
Symbiotic microalgal–bacterial biofilms can be very attractive for municipal wastewater treatment. Microalgae remove nitrogen and phosphorus and simultaneously produce the oxygen that is required for the aerobic, heterotrophic degradation of organic pollutants. For the application of these biofilms in new wastewater treatment systems, the engineering aspects need to be investigated to obtain a balanced system where no additional oxygen is required. In this study symbiotic microalgal–bacterial biofilms were grown in flow cells with ammonium and phosphate, and with acetate as biodegradable organic pollutant at a hydraulic retention time of 4.5 h. The symbiotic biofilms removed acetate from 323 mg/L to 39 mg/L without an external oxygen or carbon dioxide supply at a removal rate of 43 g COD/m2/d. Ammonium and phosphate could not be completely removed, but removal rates of 3.2 g/m2/d and 0.41 g/m2/d were obtained, respectively. Further nitrogen removal may be obtained by nitrification and denitrification as the biofilm obtained a considerable heterotrophic denitrification capacity. The symbiotic relationship between microalgae and aerobic heterotrophs was proven by subsequently removing light and acetate. In both cases this resulted in the cessation of the symbiosis and in increasing effluent concentrations of both acetate and the nutrients ammonium and phosphate. Future research should investigate the dimensioning of an up-scaled symbiotic biofilm reactor, and the possibilities to obtain additional nitrogen and phosphorus removal under day–night cycles utilizing real wastewater.
Microbial Community Analysis of a Methane-Producing Biocathode in a bioelectrochemical System
Eerten-Jansen, M.C.A.A. van; Veldhoen, A.B. ; Plugge, C.M. ; Stams, A.J.M. ; Buisman, C.J.N. ; Heijne, A. ter - \ 2013
Archaea : an international microbiological journal 2013 (2013). - ISSN 1472-3646 - 12 p.
caeni sp nov. - fuel-cells - bacterial adhesion - activated-sludge - electrolysis cells - carbon-dioxide - gen. nov. - performance - reduction - acetate
A methane-producing biocathode that converts CO2 into methane was studied electrochemically and microbiologically. The biocathode produced methane at a maximum rate of 5.1¿L¿CH4/m2 projected cathode per day (1.6¿A/m2) at -0.7¿V versus NHE cathode potential and 3.0¿L¿CH4/m2 projected cathode per day (0.9¿A/m2) at -0.6¿V versus NHE cathode potential. The microbial community at the biocathode was dominated by three phylotypes of Archaea and six phylotypes of bacteria. The Archaeal phylotypes were most closely related to Methanobacterium palustre and Methanobacterium aarhusense. Besides methanogenic Archaea, bacteria seemed to be associated with methane production, producing hydrogen as an intermediate. Biomass density varied greatly with part of the carbon electrode covered with a dense biofilm, while only clusters of cells were found on other parts. Based on our results, we discuss how inoculum enrichment and changing operational conditions may help to increase biomass density and to select for microorganisms that produce methane.
Influence of membrane type, current and potential on the response to chemical toxicants of a microbial fuel cell based biosensor
Stein, N.E. ; Hamelers, H.V.M. ; Buisman, C.J.N. - \ 2012
Sensors and Actuators B: Chemical 163 (2012)1. - ISSN 0925-4005 - p. 1 - 7.
ion-exchange membranes - industrial waste-water - vibrio-fischeri - biocatalyzed electrolysis - activated-sludge - performance - transport - toxicity - sensor - wastewaters
Drinking water free of chemical toxicants is important for people's health. A microbial fuel cell based biosensor can be used to detect the presence of toxic chemicals. The sensitivity of this type of biosensor for nickel was investigated. There was no delay in the response of the sensor and the sensitivity was 0.0027 A/m2/mg Ni/l at an anode potential of -0.4 V. The effect of four types of ion exchange membranes (cation exchange, anion exchange, monovalent cation exchange and bipolar membranes) on the sensitivity was not significant. Current density correlates with the decrease of the nickel concentration in the sensor with 16.5 mg/l/A/m2 by causing a flux of nickel towards the membrane and the catholyte. However, the sensitivity is higher at higher overpotential and thus at higher current density. Thus although nickel concentration is lower, the response is higher at high overpotentials. The sensitivity still has to be increased because even at an overpotential of -0.16 V the sensitivity is too low to be able to measure the concentrations that is maximally allowed by European directives on (drinking) water quality.
Microbial community structure elucidates performance of Glyceria maxima plant microbial fuel cell
Timmers, R.A. ; Rothballer, M. ; Strik, D.P.B.T.B. ; Engel, M. ; Schulz, M. ; Hartmann, A. ; Hamelers, H.V.M. ; Buisman, C.J.N. - \ 2012
Applied Microbiology and Biotechnology 94 (2012)2. - ISSN 0175-7598 - p. 537 - 548.
targeted oligonucleotide probes - iron-reducing bacteria - in-situ hybridization - electricity-generation - fe(iii)-reducing bacterium - shewanella-putrefaciens - activated-sludge - soil bacteria - rice plants - human feces
The plant microbial fuel cell (PMFC) is a technology in which living plant roots provide electron donor, via rhizodeposition, to a mixed microbial community to generate electricity in a microbial fuel cell. Analysis and localisation of the microbial community is necessary for gaining insight into the competition for electron donor in a PMFC. This paper characterises the anode-rhizosphere bacterial community of a Glyceria maxima (reed mannagrass) PMFC. Electrochemically active bacteria (EAB) were located on the root surfaces, but they were more abundant colonising the graphite granular electrode. Anaerobic cellulolytic bacteria dominated the area where most of the EAB were found, indicating that the current was probably generated via the hydrolysis of cellulose. Due to the presence of oxygen and nitrate, short-chain fatty acid-utilising denitrifiers were the major competitors for the electron donor. Acetate-utilising methanogens played a minor role in the competition for electron donor, probably due to the availability of graphite granules as electron acceptors.
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
Effect of temperature shocks on membrane fouling in membrane bioreactors
Brink, P. van den; Satpradit, O.A. ; Bentem, A. van; Zwijnenburg, A. ; Temmink, B.G. ; Loosdrecht, M.C.M. - \ 2011
Water Research 45 (2011)15. - ISSN 0043-1354 - p. 4491 - 4500.
afvalwaterbehandeling - bioreactoren - membranen - geactiveerd slib - temperatuur - vervuiling door afzetting - viscositeit - waste water treatment - bioreactors - membranes - activated sludge - temperature - fouling - viscosity - waste-water treatment - cross-flow microfiltration - flux-step method - activated-sludge - particle deposition - size distribution - light-scattering - bubble-size - performance - ultrafiltration
Temperature is known to influence the biological performance of conventional activated sludge systems. In membrane bioreactors (MBRs), temperature not only affects the bioconversion process but is also shown to have an effect on the membrane performance. Four phenomena are generally reported to explain the higher resistance for membrane filtration found at lower temperatures: (1) increased mixed liquor viscosity, reducing the shear stress generated by coarse bubbles, (2) intensified deflocculation, reducing biomass floc size and releasing EPS into the mixed liquor, (3) lower backtransport velocity and (4) reduced biodegradation of COD. Although the higher resistance at low temperatures has been reported in several papers, the relation with supernatant composition has not been investigated before. In this paper, the composition of the soluble fraction of the mixed liquor is related to membrane performance after exposing the sludge to temperature shocks. Flux step experiments were performed in an experimental system at 7, 15, and 25° Celsius with sludge that was continuously recirculated from a pilot-scale MBR. After correcting the permeate viscosity for temperature, higher membrane fouling rates were obtained for the lower temperature in combination with low fouling reversibility. The soluble fraction of the MBR mixed liquor was analysed for polysaccharides, proteins and submicron particle size distribution. At low temperature, a high polysaccharide concentration was found in the experimental system as compared to the MBR pilot. Upon decreasing the temperature of the mixed liquor, a shift was found in particle size towards smaller particles. These results show that the release of polysaccharides and/or submicron particles from sludge flocs could explain the increased membrane fouling at low temperatures
Operation of an aquatic worm reactor suitable for sludge reduction at large scale
Hendrickx, T.L.G. ; Elissen, H.J.H. ; Temmink, B.G. ; Buisman, C.J.N. - \ 2011
Water Research 45 (2011)16. - ISSN 0043-1354 - p. 4923 - 4929.
afvalwaterbehandeling - huishoudens - rioolslib - geactiveerd slib - bioreactoren - ontwerp - slibzuivering - aquatische wormen - oligochaeta - waste water treatment - households - sewage sludge - activated sludge - bioreactors - design - sludge treatment - aquatic worms - oligochaeta - eating waste sludge - activated-sludge
Treatment of domestic waste water results in the production of waste sludge, which requires costly further processing. A biological method to reduce the amount of waste sludge and its volume is treatment in an aquatic worm reactor. The potential of such a worm reactor with the oligochaete Lumbriculus variegatus has been shown at small scale. For scaling up purposes, a new configuration of the reactor was designed, in which the worms were positioned horizontally in the carrier material. This was tested in a continuous experiment of 8 weeks where it treated all the waste sludge from a lab-scale activated sludge process. The results showed a higher worm growth rate compared to previous experiments with the old configuration, whilst nutrient release was similar. The new configuration has a low footprint and allows for easy aeration and faeces collection, thereby making it suitable for full scale application.
Fate of hormones and pharmaceuticals during combined anaerobic treatment and nitrogen romoval by partial nitritation-anammox in vacuum collected black water
Graaff, M.S. de; Vieno, N.M. ; Kujawa, K. ; Zeeman, G. ; Temmink, B.G. ; Buisman, C.J.N. - \ 2011
Water Research 45 (2011)1. - ISSN 0043-1354 - p. 375 - 383.
sewage-treatment plants - personal care products - waste-water - activated-sludge - aquatic environment - musk fragrances - surface waters - estrogens - antibiotics - behavior
Vacuum collected black (toilet) water contains hormones and pharmaceuticals in relatively high concentrations (mu g/L to mg/L range) and separate specific treatment has the potential of minimizing their discharge to surface waters. In this study, the fate of estrogens (natural and synthetical hormones) and pharmaceuticals (paracetamol, metoprolol, propranolol, cetirizine, doxycycline, tetracycline, ciprofloxacin, trimethoprim, carbamazepine, ibuprofen and diclofenac) in the anaerobic treatment of vacuum collected black water followed by nitrogen removal by partial nitritation-anammox was investigated. A new analytical method was developed to detect the presence of several compounds in the complex matrix of concentrated black water. Detected concentrations in black water ranged from 1.1 mu g/L for carbamazepine to >1000 mu g/L for paracetamol. Anaerobic treatment was only suitable to remove the majority of paracetamol (>90%). Metoprolol was partly removed (67%) during aerobic treatment. Deconjugation could have affected the removal efficiency of ibuprofen as concentrations even increased during anaerobic treatment and only after the anammox treatment 77% of ibuprofen was removed. The presence of persistent micro-pollutants (diclofenac, carbamazepine and cetirizine), which are not susceptible for biodegradation, makes the application of advanced physical and chemical treatment unavoidable. (C) 2010 Elsevier Ltd. All rights reserved.
Effect of substrate feeding on viscosity evolution of anaerobic granular sludges
Pevere, A. ; Abzac, P. D'; Hullebusch, E. ; Lens, P.N.L. ; Guibaud, G. - \ 2010
Water Science and Technology 62 (2010)1. - ISSN 0273-1223 - p. 132 - 139.
polymeric substances - rheological characterization - extracellular polymers - activated-sludge - uasb reactors - waste-water - wastewaters - extraction - dynamics - biofilms
This work aims to describe the effect of the feeding regime of anaerobic activity tests on the limit viscosity (mu(lim)) evolution of the granules. Batch experiments were performed with 3 different sources of substrate: acetate, peptone, and glucose. Despite, the substrate origin was shown to affect the mu(lim) evolution of granules, no clear relationship was found between the mu(lim) evolution, type of substrate and other granule physico-chemical characteristics (i.e. pH; % of Volatile Suspended Solid; concentration of exopolymeric substances, divalent cations, P and S). The origin of granules and the substrate feeding regime modify the surface shape of the granules and may change granule-granule interactions under a shear stress, thus affecting the evolution of the v value during long term reactor operation.
Sequential anaerobic-aerobic treatment for domestic wastewater - A review
Kassab, G. ; Halalsheh, M. ; Klapwijk, A. ; Fayyad, M. ; Lier, J.B. van - \ 2010
Bioresource Technology 101 (2010)10. - ISSN 0960-8524 - p. 3299 - 3310.
rotating biological contactor - dissolved air flotation - hanging sponge reactor - baffled filter reactor - sewage-treatment - uasb reactor - performance evaluation - activated-sludge - aerated biofilter - trickling filter
Introduction, consolidation and even standardization of expensive conventional aerobic systems for domestic wastewater treatment imposed significant financial constraints on the expansion of sanitary services including treatment in developing countries. A viable alternative is the sequential anaerobic-aerobic systems. If compared with the conventional aerobic technologies based on activated sludge processes, lower energy consumption and lower excess sludge production can be achieved with a high-rate anaerobic pre-treatment step. Particularly with concentrated sewage, the energy benefit of applying anaerobic pre-treatment will become very significant. This study aims on putting the effectiveness of sequential systems for treatment of domestic wastewater on view, through displaying results presented in literature on the performance of these systems.
Extraction of extracellular polymeric substances (EPS) from anaerobic granular sludges: comparison of chemical and physical extraction protocols
Abzac, P. D'; Bordas, F. ; Hullebusch, E. ; Lens, P.N.L. ; Guibaud, G. - \ 2010
Applied Microbiology and Biotechnology 85 (2010)5. - ISSN 0175-7598 - p. 1589 - 1599.
activated-sludge - waste-water - polysaccharides - complexation - flocs - acid
The characteristics of the extracellular polymeric substances (EPS) extracted with nine different extraction protocols from four different types of anaerobic granular sludge were studied. The efficiency of four physical (sonication, heating, cationic exchange resin (CER), and CER associated with sonication) and four chemical (ethylenediaminetetraacetic acid, ethanol, formaldehyde combined with heating, or NaOH) EPS extraction methods was compared to a control extraction protocols (i.e., centrifugation). The nucleic acid content and the protein/polysaccharide ratio of the EPS extracted show that the extraction does not induce abnormal cellular lysis. Chemical extraction protocols give the highest EPS extraction yields (calculated by the mass ratio between sludges and EPS dry weight (DW)). Infrared analyses as well as an extraction yield over 100% or organic carbon content over 1 g g(-1) of DW revealed, nevertheless, a carry-over of the chemical extractants into the EPS extracts. The EPS of the anaerobic granular sludges investigated are predominantly composed of humic-like substances, proteins, and polysaccharides. The EPS content in each biochemical compound varies depending on the sludge type and extraction technique used. Some extraction techniques lead to a slightly preferential extraction of some EPS compounds, e.g., CER gives a higher protein yield.
Effects of extraction procedures on metal binding properties of extracellular polymeric substances (EPS) from anaerobic granular sludges
Abzac, P. D'; Bordas, F. ; Hullebusch, E. ; Lens, P.N.L. ; Guibaud, G. - \ 2010
Colloids and Surfaces. B: Biointerfaces 80 (2010)2. - ISSN 0927-7765 - p. 161 - 168.
activated-sludge - titration data - biosorption - cadmium - complexation - adsorption - sorption - lead - cd - constants
The effects of the extraction procedure of extracellular polymeric substances (EPS) on their proton/metal binding properties were studied. Nine extraction procedures (one control, four physical and four chemical procedures) were applied to four types of anaerobic granular sludges. The binding capacities between the EPS and lead or cadmium were investigated at pH 7 by a polarographic method. The composition of the EPS extracts varied according to the extraction technique and the origin of the sludge. This induced differences in the pK(a)s and the binding sites density of the EPS extracts. The carry-over of the extractant in the samples strongly affects the properties of the EPS from chemical extraction protocols. Lead and cadmium seem to be bound differently with the EPS, a higher binding capacity was observed for Pb2+ than for Cd2+.
Influence of membrane properties on fouling in submerged membrane bioreactors
Marel, P. van der; Zwijnenburg, A. ; Kemperman, A. ; Wessling, M. ; Temmink, B.G. ; Meer, W. van der - \ 2010
Journal of Membrane Science 348 (2010)1-2. - ISSN 0376-7388 - p. 66 - 74.
waste-water treatment - cross-flow microfiltration - subcritical flux operation - activated-sludge - step method - filtration - ultrafiltration - deposition - morphology - colloids
Polymeric flat-sheet membranes with different properties were used in filtration experiments with activated sludge from a pilot-scale MBR to investigate the influence of membrane pore size, surface porosity, pore morphology, and hydrophobicity on membrane fouling. An improved flux-step method was used to measure both the critical flux and critical flux for irreversibility. Long term experiments were performed to evaluate if influences of membrane properties on short term could be translated to long term fouling behavior. The results showed that a hydrophilic asymmetric membrane with an interconnected pore structure, a nominal pore size of 0.3 µm, and large surface porosity of 27%, provided the best membrane performance with respect to critical flux and critical flux for irreversibility. The dominant fouling mechanism in long term filtration experiments was gel layer formation, which for this membrane was the least severe, and therefore extended the sustainable time.
Aquatic worms eat sludge: mass balances and processing of worm faeces
Hendrickx, T.L.G. ; Temmink, B.G. ; Elissen, H.J.H. ; Buisman, C.J.N. - \ 2010
Journal of Hazardous Materials 177 (2010)1-3. - ISSN 0304-3894 - p. 633 - 638.
waste-water-treatment - activated-sludge - reduction - removal - reactor
Reduction of the amount of waste sludge from waste water treatment plants (WWTPs) can be achieved with the aquatic worm Lumbriculus variegatus in a new reactor concept. In addition to reducing the amount of waste sludge, further processing of produced worm faeces and released nutrients should also be considered. This study gives the mass balances for sludge consumed by L. variegatus, showing the fate of the consumed organic material, nutrients and heavy metals associated with the sludge. A distinction is made between conversion into worm biomass, release as dissolved metabolites and what remains in the worm faeces. The results showed that 39% of the nitrogen and 12% of the phosphorus in the sludge digested by the worms are used in the formation of new worm biomass, which has potential for reuse. Experiments showed that settling of the worm faeces leads to a factor 2.5 higher solids concentration, compared to settling of waste sludge. This could lead to a 67% reduction of the volumetric load on thickening equipment. The worm reactor is expected to be most interesting for smaller WWTPs where a decrease on the volumetric load on sludge handling operations will have most impact