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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    Ecophysiology of sulfate-reducing bacteria and syntrophic communities in marine anoxic sediments
    Özüölmez, Deya - \ 2017
    Wageningen University. Promotor(en): A.J.M. Stams; Caroline M. Plugge. - Wageningen : Wageningen University - ISBN 9789463436540 - 225
    degradation - marine sediments - methanobacteria - microorganisms - organic matter - anoxia - sulfate reduction - degradatie - mariene sedimenten - methanobacteria - micro-organismen - organische stof - anoxie - sulfaatreductie

    Propionate, butyrate, acetate, hydrogen and formate are the major intermediates of organic matter degradation. Sulfate-reducing bacteria (SRB) contribute significantly to the consumption of these substrates in sulfate-rich marine sediments. In sulfate-depleted sediments, however, complete degradation of propionate or butyrate is only possible via syntrophic cooperation of acetogenic bacteria and methanogenic archaea. Despite that the predominance of SRB in sulfate-rich and methanogens in sulfate-depleted sediments was reported, recent studies showed that both types of microorganism could be present in upper and lower parts of marine sediments. In this thesis, propionate and butyrate conversions and the involved microbial community in sulfate, sulfate-methane transition and methane zone sediment of Aarhus Bay, Denmark were studied using sediment slurry incubations. Interspecies hydrogen transfer and coexistence during acetate degradation were investigated in mixed pure cultures.

    In Chapter 2, interspecies hydrogen transfer between aceticlastic Methanosaeta concilii and hydrogenotrophic microorganisms, Desulfovibrio vulgaris or Methanococcus maripaludis, was investigated. Additionally, coexistence of M. concilii and Desulfobacter latus growing on acetate under sulfidogenic conditions was studied. The results of Chapter 2 showed that D. vulgaris could reduce sulfate and grow on leaked hydrogen from M. concilii. Hydrogen leakage from M. concilii provides an explanation for biogeochemical zonation both for competitive (e.g. acetate) and non-competitive substrates (methyl compounds), and this indicates the possible coexistence of SRB and methanogens in sulfate-rich environments.

    In chapter 3 and 4, long term incubations were examined focusing on butyrate and propionate conversion and the microbial community dynamics in sediment slurry enrichments at different sulfate (o, 3 and 20 mM) concentrations and incubation temperatures (10°C and 25°C). Sulfate reduction is the dominant process for butyrate and propionate conversion in Aarhus Bay sediments. In the absence of sulfate, both substrates can be converted efficiently, indicating the presence of syntrophic communities throughout the sediment. The fluctuating methane concentrations and the enrichment of anaerobic methanotrophic archaea (ANME) during butyrate and propionate conversion at 10°C suggest the occurrence of anaerobic oxidation of methane (AOM) in sulfate-methane transition zone (SMTZ) of Aarhus Bay.

    The microbial community involved in butyrate and propionate conversions were investigated using next generation sequencing (NGS) of the 16S rRNA amplicon sequencing. The enriched sulfate-reducing bacteria at high sulfate concentration (20 mM) were different when butyrate and propionate were used as substrate. Desulfosarcina and Desulfobacterium dominate the butyrate-converting slurries (Chapter 3), whereas Desulfosarcina, Desulfobulbus and Desulforhopalus are the main SRB in propionate-converting slurries (Chapter 4). The increase in the relative abundance of Desulfobacteraceae and Desulfobulbaceae in SZ, SMTZ and MZ sediment slurries suggests the presence of sulfate reducers throughout the anoxic sediment column. In the absence of sulfate, Syntrophomonas and Cyrptanaerobacter become dominant which suggests their role in syntrophic butyrate and propionate conversion, respectively. These results were further supported in Chapter 6. The increase in the relative abundance of Syntrophomonas in the presence of sulfate (Chapter 3) and some members of Desulfobacteraceae (Chapter 4) in the absence of sulfate shows the metabolic flexibility of the microorganisms at different sulfate concentrations. Temperature has an impact on the microbial community (Chapter 4) and IPL composition (Chapter 5) in enrichment slurries. Cryptanaerobacter is dominant at 25°C, and, Desulfobacteraceae (Desulfofaba), especially Desulfobulbaceae members (Desulfobulbus, Desulforhopalus) become dominant at 10°C at 0 and 3 mM sulfate concentrations in propionate-amended enrichment slurries. In butyrate-amended slurries, Clostridiales have higher relative abundance at 10°C regardless of the sulfate concentration and the sediment depth which supports important role of Clostridiales in butyrate conversion in marine sediments. Archaeal community analyses revealed the dominance of hydrogenotrophic methanogens belonging to Methanomicrobiales in both butyrate- and propionate-converting slurries (Chapter 3 and 4) and enrichment cultures (Chapter 6) regardless of the sediment depth, the incubation temperature and the presence of sulfate, which indicate that they are the main syntrophic partners of butyrate and propionate degraders. The other syntrophic partner organisms are the aceticlastic methanogenic families: Methanosarcinaceae and Methanosaetaeceae. The presence of methane-oxidizing archaea (ANME-1b) in low temperature SMTZ slurries together with Desulfobacteraceae (Chapter 3 and 4) suggests the occurrence of anaerobic oxidation of methane (AOM) in SMTZ of Aarhus Bay.

    In conclusion, this thesis confirms the presence and activity of methanogens in sulfate-rich, and SRB in sulfate-depleted marine sediments; and their involvement in butyrate, propionate and acetate conversion. Novel bacterial and archaeal members enriched in the sediment slurries are likely involved in propionate, butyrate and acetate conversions at different depths of marine sediments in addition to known the cultured species.

    Microbacter margulisiae gen. nov., sp. nov., a novel propionigenic bacterium isolated from sediments of an acid rock drainage pond
    Sanchez Andrea, I. ; Luis Sanz, J. ; Stams, A.J.M. - \ 2014
    International Journal of Systematic and Evolutionary Microbiology 64 (2014)12. - ISSN 1466-5026 - p. 3936 - 3942.
    treating mine drainage - sulfate reduction - plant residue - waste-water - field soil - environment
    A novel anaerobic propionigenic bacterium, strain ADRIT, was isolated from sediment of an acid rock drainage environment (Tinto River, Spain). Cells were small (0.4-0.6 x 1-1.7 µm), non-motile and non-spore forming rods. Cells possessed a Gram-negative cell wall structure and were vancomycin resistant. The strain ADRIT utilized yeast extract and various sugars as substrates and formed propionate, lactate and acetate as major fermentation products. The optimum growth temperature was 30 °C and the optimum pH was 6.5, but strain ADRIT was able to grow at pH as low as 3.0. Oxidase, indole formation, and urease and catalase activities were negative. Aesculin and gelatin were hydrolysed. The predominant CFAs of strain ADRIT were anteiso-C15¿:¿0 (30.3%), iso-C15:0 (29.1%) and iso-C17:0 3-OH (14.9%). Major menaquinones were MK-8 (52%) and MK-9 (48%). The genomic DNA G+C content was 39.9 mol%. Phylogenetically, strain ADRIT was affiliated to the Porphyromonadaceae family of Bacteroidetes phylum. The closest cultured species were Paludibacter propionicigenes with 16S rRNA gene sequence similarity of 87.5% and several Dysgonomonas strains (similarities of 83.5-85.4 to the type strains). Based on the distinctive ecological, phenotypic and phylogenetic characteristics of strain ADRIT, a new genus and species Microbacter margulisiae gen. nov., sp. nov., is proposed. The type strain is ADRIT (=JCM 19374T =DSM 27471T).
    Simultaneous sulfate reduction and metal precipitation in an inverse fluidized bed reactor
    Villa Gomez, D.K. - \ 2013
    Wageningen University. Promotor(en): Piet Lens, co-promotor(en): Karel Keesman. - [S.l.] : S.n. - ISBN 9789461737410 - 194
    wervelbedden - uitrusting - sulfaatreductie - chemische precipitatie - metalen - fluidized beds - equipment - sulfate reduction - chemical precipitation - metals
    The effect of sub-optimal temperature on specific sulfidogenic activity of mesophilic SRB in an H-2-fed membrane bioreactor
    Nevatalo, L.M. ; Bijmans, M.F.M. ; Lens, P.N.L. ; Kaksonen, A.H. ; Puhakka, J.A. - \ 2010
    Process Biochemistry 45 (2010)3. - ISSN 1359-5113 - p. 363 - 368.
    gas-lift reactor - sulfate reduction - waste-water - retention time - carbon source - metal - bacteria - hydrogen - sulfide - growth
    The sulfidogenic activity of two mesophilic sulfate reducing enrichment cultures was studied in H-2-fed membrane bioreactors. The two enrichment cultures had different origins; one of them was a mesophilic and the other a psychrotolerant mesophilic culture. The operational temperatures of the reactors were gradually changed: for one the temperature was increased from 9 to 30 degrees C and for the other it was decreased from 35 to 9 degrees C. The specific sulfidogenic activities were 21-31, 52-53 and 57-92 mmol SO42- g VSS-1 d(-1) at 9, 15 and 30-35 degrees C, respectively. The sulfate reduction rate of the SRB stabilized to a lower level after the temperature was decreased. The percent electron flow to sulfate reduction was on average 24-32, 50 and 47-69% at 9, 15 and 30-35 degrees C, respectively. The capability of mesophilic SRB to oxidize electron donor decreased as the temperature was decreased. The results indicate that starting of the reactor operation at 9 degrees C resulted in higher sulfidogenic activity at suboptimal temperatures and selective enrichment of the psychrotolerant species improved. The start-up of the reactor at 35 degrees C resulted in decreased sulfidogenic activity as the temperature was decreased. This indicates that the operational temperature of bioreactors with mesophilic SRB can be decreased to 15-20 degrees C and the sulfidogenic activity will decrease by 10-40%. Moreover, an operational temperature of 9 degrees C seems to be close to the lower limit of active sulfate reduction for the mesophilic enrichment cultures used in this study.
    Reductive decolorization of the azo dye RR2 in the absence and presence of redox mediator and the electrons acceptor nitrate
    Brauna, C.H.D. ; Mota, S. ; Santos, A.B. dos - \ 2009
    Engenharia Sanitaria e Ambiental 14 (2009)2. - ISSN 1413-4152 - p. 275 - 284.
    anaerobic granular sludge - uasb reactor - textile wastewaters - sulfate reduction - biodegradation - riboflavin - pollutants - quinones - removal - color
    This paper aimed at evaluating the effect of nitrate on anaerobic azo dye reduction by using mesophilic bioreactors, in the absence and in the presence of redox mediators. Two anaerobic bioreactors were operated in parallel with a hydraulic retention time (HRT) of ten hours; ethanol was used as co-substrate. The results showed that the bioreactors were efficient on dye reduction, and the ethanol showed to be a good electron donor to sustain it. The redox mediator AQDS increased the rates of reductive decolourisation, but its effect was not so remarkable compared to the previous experiments conducted. Contrary to the raised hypothesis that nitrate addition could decrease the colour removal efficiency and catalytic properties of the redox mediators, no effect of nitrate was observed in the bioreactors
    Bioaugmentation of UASB reactors with immobilized Sulfurospirillum barnesii for simultaneous selenate and nitrate removal
    Lenz, M. ; Enright, A.M. ; O’Flaherty, V. ; Aelst, A.C. van; Lens, P.N.L. - \ 2009
    Applied Microbiology and Biotechnology 83 (2009)2. - ISSN 0175-7598 - p. 377 - 388.
    anaerobic granular sludge - waste-water treatment - respiring bacteria - elemental selenium - sulfate reduction - precipitation - remediation - bioreactors - chain - se
    Whole-cell immobilization of selenate-respiring Sulfurospirillum barnesii in polyacrylamide gels was investigated to allow the treatment of selenate contaminated (790¿µg Se¿×¿L-1) synthetic wastewater with a high molar excess of nitrate (1,500 times) and sulfate (200 times). Gel-immobilized S. barnesii cells were used to inoculate a mesophilic (30°C) bioreactor fed with lactate as electron donor at an organic loading rate of 5 g chemical oxygen demand (COD)¿×¿L-1 day-1. Selenate was reduced efficiently (>97%) in the nitrate and sulfate fed bioreactor, and a minimal effluent concentration of 39¿µg Se¿×¿L-1 was obtained. Scanning electron microscopy with energy dispersive X-ray (SEM–EDX) analysis revealed spherical bioprecipitates of =2¿µm diameter mostly on the gel surface, consisting of selenium with a minor contribution of sulfur. To validate the bioaugmentation success under microbial competition, gel cubes with immobilized S. barnesii cells were added to an Upflow Anaerobic Sludge Bed (UASB) reactor, resulting in earlier selenate (24 hydraulic retention times (HRTs)) and sulfate (44 HRTs) removal and higher nitrate/nitrite removal efficiencies compared to a non-bioaugmented control reactor. S. barnesii was efficiently immobilized inside the UASB bioreactors as the selenate-reducing activity was maintained during long-term operation (58 days), and molecular analysis showed that S. barnesii was present in both the sludge bed and the effluent. This demonstrates that gel immobilization of specialized bacterial strains can supersede wash-out and out-competition of newly introduced strains in continuous bioaugmented systems. Eventually, proliferation of a selenium-respiring specialist occurred in the non-bioaugmented control reactor, resulting in simultaneous nitrate and selenate removal during a later phase of operation
    Selective recovery of nickel over iron from a nickel-iron solution using microbial sulfate reduction in a gas-lift bioreactor
    Bijmans, M.F.M. ; Helvoort, P.J. van; Dar, S. ; Dopson, M. ; Lens, P.N.L. ; Buisman, C.J.N. - \ 2009
    Water Research 43 (2009)3. - ISSN 0043-1354 - p. 853 - 861.
    mijnbouw - metallurgie - mijnafval - slib - waterstof - ijzer - nikkel - bioreactoren - elektroforese - sulfaatreductie - slibzuivering - verwijdering - mining - metallurgy - mine tailings - sludges - hydrogen - iron - nickel - bioreactors - electrophoresis - sulfate reduction - sludge treatment - removal - gradient gel-electrophoresis - sulfide precipitation - metal precipitation - heavy-metals - soils - water - ores
    Process streams with high concentrations of metals and sulfate are characteristic for the mining and metallurgical industries. This study aims to selectively recover nickel from a nickel-iron-containing solution at pH 5.0 using a single stage bioreactor that simultaneously combines low pH sulfate reduction and metal-sulfide formation. The results show that nickel was selectively precipitated in the bioreactor at pH 5.0 and the precipitates consisted of >or=83% of the nickel content. The nickel-iron precipitates were partly crystalline and had a metal/sulfur ratio of 1, suggesting these precipitates were NiS and FeS. Experiments focusing on nickel recovery at pH 5.0 and 5.5 reached a recovery of >99.9%, resulting in a nickel effluent concentration
    Microbial aspects of anaerobic methane oxidation with sulfate as electron acceptor
    Jagersma, C.G. - \ 2009
    Wageningen University. Promotor(en): Fons Stams, co-promotor(en): Piet Lens. - [S.l. : S.n. - ISBN 9789085855118 - 181
    methaan - anaërobe omstandigheden - sulfaatreductie - anaërobe microbiologie - methane - anaerobic conditions - sulfate reduction - anaerobic microbiology
    Anaerobic oxidation of methane (AOM) is an important methane sink in the ocean but the microbes responsible for AOM are as yet resilient to cultivation. It was shown that AOM was coupled to sulfate reduction (SR) and this gave rise to current research which aims to develop a biotechnological process in which methane is used an electron donor for SR.
    This thesis describes the microbial analysis of an enrichment capable of high rate AOM (286 µmol.gdry coupled to SR using a novel submerged membrane bioreactor system. Initially AOM rates were extremely low (0.004 mmol L-1 d-1), but AOM and SR increased exponential over the course of 884 days to 0.60 mmol L-1 d-1. The responsible organisms doubled every 3.8 months.
    By constructing a clone library with subsequent sequencing and fluorescent in situ hybridization (FISH), we showed that the responsible methanotrophs belong to the ANME-2a subgroup of anaerobic methanotrophic archaea, and that sulfate reduction is most likely performed by sulfate reducing bacteria commonly found in association with other ANME related archaea in marine sediments. Another relevant portion of the bacterial sequences can be clustered within the order of Flavobacteriales but their role remains to be elucidated. FISH analyses showed that the ANME-2a cells occur as single cells without close contact to the bacterial syntrophic partner. Incubation with 13C labeled methane showed substantial incorporation of 13C label in the bacterial C16 fatty acids (bacterial; 20, 44 and 49%) and in archaeal lipids, archaeol and hydroxyl-archaeol (21 and 20%, respectively). This confirms that both archaea and bacteria are responsible for the anaerobic methane oxidation in a bioreactor enrichment inoculated with Eckernförde bay sediment. To unravel the pathway of this syntrophic conversion, the effect of possible intermediates on AOM and SR was assessed.
    To investigate which kind of waste and process streams can be treated by the methanotrophic sulfate-reducing enrichment, the effect of environmental conditions and different substrates was assessed. The optimum pH, salinity and temperature for SR with methane by the enrichment were 7.5, 30‰ and 20°C, respectively. The biomass had a good affinity for sulfate (Km < 1.0 mM), a low affinity for methane (Km > 75 KPa) and AOM was completely inhibited at 2.4 (±0.1) mM sulfide. The enrichment utilized sulfate, thiosulfate, sulfite and elemental sulfur as alternative electron acceptors for methane oxidation and formate, acetate and hydrogen as alternative electron donors for sulfate reduction. As a co-substrate for methane oxidation only methanol stimulated the conversion of 13C labeled CH4 to 13CO2 in batch incubations of Eckernförde bay sediment, other possible co-substrates had a negative effect on the AOM rate.
    The research described in this thesis shows the possibility of enriching slow growing methane oxidizing communities but also shows the difficulties in applying this process for a biotechnological purpose because of the extreme slow doubling times and the lack of understanding of the metabolic routes used by these organisms.

    Biotechnological aspects of anaerobic oxidation of methane coupled to sulfate reduction
    Meulepas, R.J.W. - \ 2009
    Wageningen University. Promotor(en): Cees Buisman, co-promotor(en): Piet Lens; Fons Stams. - [S.l. : S.n. - ISBN 9789085853978 - 173
    anaërobe omstandigheden - oxidatie - methaan - microbiologie - biotechnologie - anaërobe microbiologie - sulfaatreductie - anaerobic conditions - oxidation - methane - microbiology - biotechnology - anaerobic microbiology - sulfate reduction
    Sulfate reduction (SR) can be used for the removal and recovery of metals and oxidized sulfur compounds from waste streams. Sulfate-reducing bacteria reduce oxidized sulfur compounds to sulfide. Subsequently, sulfide can precipitate dissolved metals or can be oxidized to elemental sulfur. Both metal sulfides and elemental sulfur can be reused in various applications. SR with hydrogen or ethanol as electron donor is an established biotechnological process. However, the costs of these electron donors limit the application possibilities. Methane would be a cheaper and more attractive electron donor. SR coupled to the anaerobic oxidation of methane (AOM) occurs in marine sediments. Uncultured archaea, distantly related to methanogens, and bacteria are involved in this process. The in vitro demonstration of SR coupled to AOM gave rise to this research, which aims to develop a biotechnological process in which methane is used as electron donor for SR.
    Three types of anaerobic granular sludge were screened for the ability to reduce sulfate with methane as electron donor. To do so, incubations were done with 13C-labeled methane. All three sludge types anaerobically oxidized 13C-labeled methane to 13C-labeled carbon dioxide. Moreover, the presence of methane enhanced the SR rate. However, AOM by sludge was not coupled to SR, but coincides with net methanogenesis. The methane-dependent SR was caused by the inhibitory effect of methane on methanogens competing (possibly in syntrophic consortia with acetogenic bacteria) with sulfate reducers for the same endogenous substrate. Therefore, anaerobic granular sludge does not form a suitable inoculum for sulfate-reducing bioreactors fed with methane.
    Well-mixed ambient-pressure submersed-membrane bioreactors, fed with sulfate and methane, were inoculated with sediment from Eckernförde Bay (Baltic Sea). Initially AOM rates were extremely low (0.004 mmol L-1 day-1), but at 15ºC AOM and SR rates increased over the course of 884 days to 0.60 mmol L-1 day-1 or 1.0 mmol gVSS-1 day-1. The AOM rate doubled approximately every 3.8 months. Molecular analyses revealed that the archaea in the obtained enrichment belonged predominately to the anaerobic methanotroph ANME-2a. Both bacteria and archaea incorporated carbon derived from 13C-labeled methane into their lipids, indicating that both were involved in AOM coupled to SR. To investigate which kind of waste streams can be treated by the methane-oxidizing sulfate-reducing enrichment, the effect of environmental conditions and alternative substrates on AOM and SR was assessed. The optimum pH, salinity and temperature for SR with methane by the enrichment were 7.5, 30‰ and 20°C, respectively. The biomass had a good affinity for sulfate (Km  1.0 mM), a low affinity for methane (Km > 75 kPa) and AOM was completely inhibited by 2.4 (±0.1) mM sulfide. The enrichment utilized sulfate, thiosulfate and sulfite as electron acceptors for methane oxidation, and methane, formate, acetate and hydrogen as electron donors for SR.
    This study shows that methane can be used as electron donor for sulfate reduction in bioreactors. However, the low growth rate of the responsible microorganisms still forms a major bottleneck for biotechnological applications.

    Selenate removal in methanogenic and sulfate-reducing upflow anaerobic sludge bed reactors
    Lenz, M. ; Hullebusch, E.D. van; Hommes, G. ; Corvini, P.F.X. ; Lens, P.N.L. - \ 2008
    Water Research 42 (2008)8-9. - ISSN 0043-1354 - p. 2184 - 2194.
    afvalwaterbehandeling - bioreactoren - slib - selenium - verwijdering - efficiëntie - biologische filtratie - slibzuivering - sulfaatreductie - waste water treatment - bioreactors - sludges - selenium - removal - efficiency - biological filtration - sludge treatment - sulfate reduction - acid-mine drainage - granular sludge - elemental selenium - respiring bacteria - waste-water - se - reduction - sediments - coal - particulate
    This paper evaluates the use of upflow anaerobic sludge bed (UASB) bioreactors (30 degrees C, pH = 7.0) to remove selenium oxyanions from contaminated waters (790 mu g Se L-1) under methanogenic and sulfate-reducing conditions using lactate as electron donor. One UASB reactor received sulfate at different sulfate to selenate ratios, while another UASB was operated under methanogenic conditions for 132 days without sulfate in the influent. The selenate effluent concentrations in the sulfate-reducing and methanogenic reactor were 24 and 8 mu gSeL(-1), corresponding to removal efficiencies of 97% and 99%, respectively. X-ray diffraction (XRD) analysis and sequential extractions showed that selenium was mainly retained as elemental selenium in the biomass. However, the total dissolved selenium effluent concentrations amounted to 73 and 80 mu gSeL(-1), respectively, suggesting that selenate was partly converted to another selenium compound, most likely colloidally dispersed Sea nanoparticles. Possible intermediates of selenium reduction (selenite, dimethylselenide, dimethyldiselenide, H2Se) could not be detected. Sulfate reducers removed selenate at molar excess of sulfate to selenate (up to a factor of 2600) and elevated dissolved sulfide concentrations (up to 168mgL(-1)), but selenium removal efficiencies were limited by the applied sulfate-loading rate. in the methanogenic bioreactor, selenate and dissolved selenium removal were independent of the sulfate load, but inhibited by sulfide (101 mg L-1). The selenium removal efficiency of the methanogenic UASB abruptly improved after 58 days of operation, suggesting that a specialized selenium-converting population developed in the reactor. This paper demonstrates that both sulfate-reducing and methanogenic UASB reactors can be applied to remove selenate from contaminated natural waters and anthropogenic waste streams, e.g. agricultural drainage waters, acid mine drainage and flue gas desulfurization bleeds.
    Selenium oxyanion inhibition of hydrogenotrophic and acetoclastic methanogenesis
    Lenz, M. ; Janzen, N. ; Lens, P.N.L. - \ 2008
    Chemosphere 73 (2008)3. - ISSN 0045-6535 - p. 383 - 388.
    anaerobic granular sludge - agricultural drainage sediment - escherichia-coli - thauera-selenatis - waste-water - elemental selenium - sulfate reduction - bed reactors - bioremediation - removal
    Inhibitory effects of selenite and selenate towards hydrogenotrophic and acetoclastic methanogenesis were evaluated in anaerobic toxicity assays. The 50% inhibitory concentration (IC50) of both selenium oxyanions was below 6.1 X 10(-5) M in hydrogenotrophic assays, whereas acetoclastic methanogens were less inhibited: IC50 = 8.3 x 10(-5) M and 5.5 x 10(-4) M for selenite and selenate, respectively. Selenite completely inhibits methanogenesis from both substrates tested at concentrations >= 10(-3) M selenite, while only marginal methanogenic activities occur at equimolar concentrations of selenate. Selenite becomes irreversibly inhibitory upon a single exposure, whereas selenate inhibits methanogens upon repeated exposure. Consequently, methane recovery can be seriously hampered or even impossible during anaerobic treatment of highly selenium contaminated waste streams.
    High rate sulfate reduction at pH 6 in a Ph-auxostat submerged membrane bioreactor fed with formate
    Bijmans, M.F.M. ; Peeters, T.W.T. ; Lens, P.N.L. ; Buisman, C.J.N. - \ 2008
    Water Research 42 (2008)10-11. - ISSN 0043-1354 - p. 2439 - 2448.
    afvalwaterbehandeling - industrieel afval - bioreactoren - membranen - filtratie - sulfaat reducerende bacteriën - sulfaatreductie - waste water treatment - industrial wastes - bioreactors - membranes - filtration - sulfate reducing bacteria - sulfate reduction - gas-lift reactor - reducing bacteria - hydrogen-sulfide - carbon-dioxide - growth - methanogenesis - conversion - removal - sludge - water
    Many industrial waste and process waters contain high concentrations of sulfate, which can be removed by sulfate-reducing bacteria (SRB). This paper reports on mesophilic (30 °C) sulfate reduction at pH 6 with formate as electron donor in a membrane bioreactor with a pH-auxostat dosing system. A mixed microbial community from full-scale industrial wastewater treatment bioreactors operated at pH 7 was used as inoculum. The pH-auxostat enabled the bacteria to convert sulfate at a volumetric activity of 302 mmol sulfate reduced per liter per day and a specific activity of 110 mmol sulfate reduced per gram volatile suspended solids per day. Biomass grew in 15 days from 0.2 to 4 g volatile suspended solids per liter. This study shows that it is possible to reduce sulfate at pH 6 with formate as electron donor at a high volumetric and specific activity with inocula from full-scale industrial wastewater treatment bioreactors operated at neutral pH. The combination of a membrane bioreactor and a pH-auxostat is a useful research tool to study processes with unknown growth rates at maximum activities.
    Sulfate reduction under acidic conditions for selective model recovery
    Bijmans, M.F.M. - \ 2008
    Wageningen University. Promotor(en): Cees Buisman, co-promotor(en): Piet Lens. - [S.l.] : S.n. - ISBN 9789085049258 - 156
    sulfaat - redoxreacties - zuurgraad - metalen - terugwinning - afvalwaterbehandeling - bioreactoren - nikkel - ijzer - sulfaatreductie - sulfate - redox reactions - acidity - metals - recovery - waste water treatment - bioreactors - nickel - iron - sulfate reduction
    Dit proefschrift heeft als doel om processen te ontwikkelen voor selectieve metaal herwinning uit afvalwater and processtromen die meerdere metalen bevatten, door gebruik te maken van sulfaat reductie onder zure omstandigheden
    Effects of flow regime and flooding on heavy metal availability in sediment and soil of a dynamic river system
    Poot, A. ; Gillissen, F. ; Koelmans, A.A. - \ 2007
    Environmental Pollution 148 (2007)3. - ISSN 0269-7491 - p. 779 - 787.
    acid-volatile sulfide - fresh-water sediments - marine-sediments - sulfate reduction - climate-change - toxicity - zinc - avs - bioavailability - floodplain
    The acid volatile sulphide (AVS) and simultaneously extracted metals (¿SEM) method is increasingly used for risk assessment of toxic metals. In this study, we assessed spatial and temporal variations of AVS and ¿SEM in river sediments and floodplain soils, addressing influence of flow regime and flooding. Slow-flowing sites contained high organic matter and clay content, leading to anoxic conditions, and subsequent AVS formation and binding of metals. Seasonality affected these processes through temperature and oxygen concentration, leading to increased levels of AVS in summer at slow-flowing sites (max. 37 ¿mol g¿1). In contrast, fast-flowing sites hardly contained AVS, so that seasonality had no influence on these sites. Floodplain soils showed an opposite AVS seasonality because of preferential inundation and concomitant AVS formation in winter (max. 3¿30 ¿mol g¿1). We conclude that in dynamic river systems, flow velocity is the key to understanding variability of AVS and ¿SEM.
    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
    Use of biogenic sulfide for ZnS precipitation
    Esposito, G. ; Veeken, A. ; Weijma, J. ; Lens, P.N.L. - \ 2006
    Separation and Purification Technology 51 (2006)1. - ISSN 1383-5866 - p. 31 - 39.
    agglomerative crystal precipitation - acid-mine drainage - sulfate reduction - metals - crystallization - biotreatment - biorecovery - kinetics - reactor - system
    A 600 ml continuously stirred tank reactor was used to assess the performance of a zinc sulfide precipitation process using a biogenic sulfide solution (the effluent of a sulfate-reducing bioreactor) as sulfide source. In all experiments, a proportional-integral (PI) control algorithm was used to control the pH and the sulfide (S2-) concentration at the desired level in the precipitator. The pS (defined as: -log [S2-]) and pH were optimised using a chemical Na2S solution as sulfide source. A S2- concentration of 10(-15) M (i.e. pS 15) was found to be optimal for zinc sulfide precipitation, resulting in a residual zinc concentration of 0.07 mg/l from a 3 g/l Zn2+ influent, for both chemical Na2S and biogenic sulfide solutions. The mean particle size of the ZnS precipitates at pS 15 and pH 6.3 was 7.5 and 10.2 mu m when using biogenic sulfide and chemical Na2S, respectively, indicating that both sulfide sources are adequate for solid-liquid separation by sedimentation. When biogenic sulfide instead of chemical Na2S was used, the efficiency of the ZnS precipitation process slightly decreased both in terms of zinc effluent concentration (at pS 10 and 20) and particle size of the precipitate (at pS 10, 15 and 20). This was shown to be attributed to the presence of various substances (phosphate, micro-nutrients, acetate, EDTA) present in the sulfate-reducing reactor effluent.
    Dynamic modelling and process control of ZnS precipitation
    König, J. ; Keesman, K.J. ; Veeken, A.H.M. ; Lens, P.N.L. - \ 2006
    Separation Science and Technology 41 (2006)6. - ISSN 0149-6395 - p. 1025 - 1042.
    reducing bacterial biofilms - sulfate reduction - heavy-metals - reactor - accumulation
    This paper presents the dynamic modelling and design of a control strategy for the ZnS precipitation process. During lab¿scale experiments, the sulfide concentration in a precipitator was controlled at a prespecified pS value by manipulating the flow from a buffer vessel. Batch tests showed that the optimal condition for zinc sulfide precipitation is at a sulfide concentration of 10¿15 mole/l (pS 15). Experiments with the precipitator showed that the sulfide concentration highly deviates from a given setpoint when proportional (P) control is used, but this deviation can be decreased using a Proportional Integral (PI) controller. Moreover, the PI controller was able to handle sudden disturbances in the process conditions (pH, influent flow rate, or zinc and sulfide concentration). Additional precipitation experiments were conducted using effluent from a sulfate reducing gas¿lift reactor to determine if the compounds present in the effluent influence the control process. With the gas¿lift reactor effluent and a PI controller, the desired sulfide concentration was reached almost instantaneously (within 15 minutes) within acceptable margins (2¿5%)
    Dispersed plug flow model for upflow anaerobic sludge bed reactors with focus on granular sludge dynamics
    Kalyuzhnyi, S.V. ; Fedorovich, V.V. ; Lens, P.N.L. - \ 2006
    Journal of Industrial Microbiology and Biotechnology 33 (2006)3. - ISSN 1367-5435 - p. 221 - 237.
    uasb-reactor - sulfate reduction - cheese whey - liquid flow - blanket - digestion - wastewater - glucose - methanogenesis - competition
    A new approach to model upflow anaerobic sludge bed (UASB)-reactors, referred to as a one-dimensional dispersed plug flow model, was developed. This model focusses on the granular sludge dynamics along the reactor height, based on the balance between dispersion, sedimentation and convection using one-dimensional (with regard to reactor height) equations. A universal description of both the fluid hydrodynamics and granular sludge dynamics was elaborated by applying known physical laws and empirical relations derived from experimental observations. In addition, the developed model includes: (1) multiple-reaction stoichiometry, (2) microbial growth kinetics, (3) equilibrium chemistry in the liquid phase, (4) major solid-liquid-gas interactions, and (5) material balances for dissolved and solid components along the reactor height. The integrated model has been validated with a set of experimental data on the start-up, operation performance, sludge dynamics, and solute intermediate concentration profiles of a UASB reactor treating cheese whey [Yan et al. (1989) Biol Wastes 27:289¿305; Yan et al. (1993) Biotechnol Bioeng 41:700¿706]. A sensitivity analysis of the model, performed with regard to the seed sludge characteristics and the key model parameters, showed that the output of the dispersed plug flow model was most influenced by the sludge settleability characteristics and the growth properties (especially ¿m) of both protein-degrading bacteria and acetotrophic methanogens
    Direct inhibition of methanogenesis by ferric iron
    Bodegom, P.M. van; Scholten, J.C.M. ; Stams, A.J.M. - \ 2004
    FEMS microbiology ecology 49 (2004)2. - ISSN 0168-6496 - p. 261 - 268.
    fe(iii) oxide reduction - rice paddy soils - methane production - microbial processes - sulfate reduction - field soil - bacteria - sediments - mineralization - microorganisms
    Observed inhibition of methanogenesis under Fe(III)-reducing conditions is usually explained by competition of methanogens and Fe(III)-reducing bacteria for the common Substrates acetate and hydrogen. However, substrate competition alone cannot explain the strong inhibition of methanogenesis during Fe(III)-reduction. We demonstrate direct inhibition of methanogenesis by amorphous Fe(OH)(3) at concentrations between 0 and 10 mM in experiments with pure cultures of inethanogens. The sensitivity toward Fe(III) was higher for Methanospirillum hungatei and Methanosarcina barkeri grown with H-2/CO2 than for Methanosaeta concilii and Methanosarcina barkeri grown with acetate. Cultures of Methanosarcina barkeri grown with H-2/CO2 and methanol demonstrated a capacity for Fe(III) reduction, which suggests that Fe(III)-reduction by methanogens may also contribute to Fe(III) inhibition of methanogenesis. Our results have important implications for kinetic modelling of microbial redox processes in anoxic soils and sediments. (C) 2004 Published by Elsevier B.V. on behalf of the Federation of European Microbiological Societies.
    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.
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