23 results on '"Boon, Nico"'
Search Results
2. Correlations between molecular and operational parameters in continuous lab-scale anaerobic reactors
- Author
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Carballa, Marta, Smits, Marianne, Etchebehere, Claudia, Boon, Nico, and Verstraete, Willy
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- 2011
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3. Microbial community dynamics reflect reactor stability during the anaerobic digestion of a very high strength and sulfate-rich vinasse
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Jiménez, Janet, Barrera, Ernesto L., De Vrieze, Jo, Boon, Nico, DeMeester, Steven, Spanjers, H., Romero, Osvaldo Romero, and Dewulf, Jo
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anaerobic digestion ,sulfate reduction ,microbial community ,vinasse ,reactor stability - Abstract
BACKGROUND: Microbial community dynamics during the anaerobic digestion of vinasse has been little studied. However, having knowledge about it is essential for early detection of reactor operational difficulties to apply preventive actions. This research studies the microbial community dynamics in the anaerobic digestion of vinasse, linking to experimental observations about product yields and organic matter degradation. RESULTS: Methane and sulfide yields decreased with increasing SO4 2-/COD ratio, while the fraction of organic matter degraded by sulfate reducing bacteria increased from 4.5 ± 0.3% to 27.1 ± 0.6%. The archaeal community showed that acetoclastic Methanosaetaceae were little affected by the increase of the SO4 2-/COD ratio, in contrast to the Methanomicrobiales and Methanobacteriales population, which decreased during the experiment. The total bacterial diversity was influenced mainly by substrate composition, showing that the increase of the SO4 2-/COD ratio above 0.10 shifted the bacterial community to a lower richness. CONCLUSION: These results provide knowledge on the dynamics of the microbial communities, which can be useful to control the anaerobic digestion of sulfate-rich vinasses, showing that reactor stability equates to the higher ratios between total methanogens and total bacteria gene copy numbers, whereas operational difficulties can be associated to lower bacterial richness and higher community organization.
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- 2018
4. Efficient molasses fermentation under high salinity by inocula of marine and terrestrial origin.
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Scoma, Alberto, Coma, Marta, Kerckhof, Frederiek-Maarten, Boon, Nico, and Rabaey, Korneel
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MOLASSES ,FERMENTATION ,SUGAR industry ,BIOCONVERSION ,SALINITY - Abstract
Background: Molasses is a dense and saline by-product of the sugar agroindustry. Its high organic content potentially fuels a myriad of renewable products of industrial interest. However, the biotechnological exploitation of molasses is mainly hampered by the high concentration of salts, an issue that is nowadays tackled through dilution. In the present study, the performance of microbial communities derived from marine sediment was compared to that of communities from a terrestrial environment (anaerobic digester sludge). The aim was to test whether adaptation to salinity represented an advantage for fermenting molasses into renewable chemicals such as volatile fatty acids (VFAs) although high sugar concentrations are uncommon to marine sediment, contrary to anaerobic digesters. Results: Terrestrial and marine microbial communities were enriched in consecutive batches at different initial pH values (pH
i ; either 6 or 7) and molasses dilutions (equivalent to organic loading rates (OLRs) of 1 or 5 gCOD L-1 d-1 ) to determine the best VFA production conditions. Marine communities were supplied with NaCl to maintain their native salinity. Due to molasses inherent salinity, terrestrial communities experienced conditions comparable to brackish or saline waters (20-47 mS cm-1 ), while marine conditions resembled brine waters (>47 mS cm-1 ). Enrichments at optimal conditions of OLR 5 gCOD L-1 d-1 and pHi 7 were transferred into packed-bed biofilm reactors operated continuously. The reactors were first operated at 5 gCOD L-1 d-1 , which was later increased to OLR 10 gCOD L-1 d-1 . Terrestrial and marine reactors had different gas production and community structures but identical, remarkably high VFA bioconversion yields (above 85%) which were obtained with conductivities up to 90 mS cm-1 . COD-to-VFA conversion rates were comparable to the highest reported in literature while processing other organic leftovers at much lower salinities. Conclusions: Although salinity represents a major driver for microbial community structure, proper acclimation yielded highly efficient systems treating molasses, irrespective of the inoculum origin. Selection of equivalent pathways in communities derived from different environments suggests that culture conditions select for specific functionalities rather than microbial representatives. Mass balances, microbial community composition, and biochemical analysis indicate that biomass turnover rather than methanogenesis represents the main limitation to further increasing VFA production with molasses. This information is relevant to moving towards molasses fermentation to industrial application. [ABSTRACT FROM AUTHOR]- Published
- 2017
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5. Enrichment of Methanosaetaceae on carbon felt and biochar during anaerobic digestion of a potassium-rich molasses stream.
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De Vrieze, Jo, Devooght, Arno, Walraedt, Diego, and Boon, Nico
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ANAEROBIC digestion ,WASTEWATER treatment ,MICROBIAL ecology ,METHANE fermentation ,MOLASSES ,POTASSIUM ,BIOGAS production - Abstract
Biorefineries allow the production of value-added chemicals, yet this also causes the formation of considerable amounts of wastewater that require suitable treatment. These biorefinery wastewaters often contain a high salinity, which inhibits methanogenesis. In this research, molasses were used to mimic these waste streams to evaluate their treatability by anaerobic digestion. Two different carrier materials, i.e., carbon felt and biochar, with similar surface properties were evaluated for their potential to stabilize anaerobic digestion of these wastewaters via active enrichment of the methanogenic community. Initial stable methane production values between 620 and 640 mL CH L day were reported in each treatment. At the end of the experiment, methane production decreased with more than 50 %, while VFA increased to values up to 20 g COD L, indicating severe process failure, due to the high potassium concentration in these wastewaters, irrespective of the presence of carrier material. However, an increased relative abundance of Methanosaetaceae both on the biochar and carbon felt was observed. In conclusion, this research demonstrated that carbon felt and biochar are both suitable carrier materials for selective enrichment of Methanosaetaceae, yet this did not lead to stable anaerobic digestion of a potassium-rich molasses waste stream. The increased relative abundance of Methanosaetaceae on both carrier materials can, nonetheless, be considered valuable in terms of alternative applications and warrants further research. [ABSTRACT FROM AUTHOR]
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- 2016
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6. Inoculum selection is crucial to ensure operational stability in anaerobic digestion.
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Vrieze, Jo, Gildemyn, Sylvia, Vilchez-Vargas, Ramiro, Jáuregui, Ruy, Pieper, Dietmar, Verstraete, Willy, and Boon, Nico
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ANAEROBIC digestion ,SEWAGE sludge digestion ,GLYCERIN ,PROTEOBACTERIA ,METHANE synthesis - Abstract
Anaerobic digestion is considered a key technology for the future bio-based economy. The microbial consortium carrying out the anaerobic digestion process is quite complex, and its exact role in terms of 'elasticity', i.e., the ability to rapidly adapt to changing conditions, is still unknown. In this study, the role of the initial microbial community in terms of operational stability and stress tolerance was evaluated during a 175-day experiment. Five different inocula from stable industrial anaerobic digesters were fed a mixture of waste activated sludge and glycerol. Increasing ammonium pulses were applied to evaluate stability and stress tolerance. A different response in terms of start-up and ammonium tolerance was observed among the different inocula. Methanosaetaceae were the dominant acetoclastic methanogens, yet, Methanosarcinaceae increased in abundance at elevated ammonium concentrations. A shift from a Firmicutes to a Proteobacteria dominated bacterial community was observed in failing digesters. Methane production was strongly positively correlated with Methanosaetaceae, but also with Bacteria related to Anaerolinaceae, Clostridiales, and Alphaproteobacteria. Volatile fatty acids were strongly positively correlated with Betaproteobacteria and Bacteroidetes, yet ammonium concentration only with Bacteroidetes. Overall, these results indicate the importance of inoculum selection to ensure stable operation and stress tolerance in anaerobic digestion. [ABSTRACT FROM AUTHOR]
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- 2015
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7. One-stage partial nitritation/anammox at 15 °C on pretreated sewage: feasibility demonstration at lab-scale.
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De Clippeleir, Haydée, Vlaeminck, Siegfried E., De Wilde, Fabian, Daeninck, Katrien, Mosquera, Mariela, Boeckx, Pascal, Verstraete, Willy, and Boon, Nico
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ANAEROBIC digestion ,OXIDATION of ammonium compounds ,CHEMICAL oxygen demand ,NITROGEN removal (Sewage purification) ,TEMPERATURE effect ,AUTOTROPHIC bacteria ,DENITRIFICATION - Abstract
Energy-positive sewage treatment can be achieved by implementation of oxygen-limited autotrophic nitrification/denitrification (OLAND) in the main water line, as the latter does not require organic carbon and therefore allows maximum energy recovery through anaerobic digestion of organics. To test the feasibility of mainstream OLAND, the effect of a gradual temperature decrease from 29 to 15 °C and a chemical oxygen demand (COD)/N increase from 0 to 2 was tested in an OLAND rotating biological contactor operating at 55–60 mg NH
4 + –N L−1 and a hydraulic retention time of 1 h. Moreover, the effect of the operational conditions and feeding strategies on the reactor cycle balances, including NO and N2 O emissions were studied in detail. This study showed for the first time that total nitrogen removal rates of 0.5 g N L−1 day−1 can be maintained when decreasing the temperature from 29 to 15 °C and when low nitrogen concentration and moderate COD levels are treated. Nitrite accumulation together with elevated NO and N2 O emissions (5 % of N load) were needed to favor anammox compared with nitratation at low free ammonia (<0.25 mg N L−1 ), low free nitrous acid (<0.9 μg N L−1 ), and higher DO levels (3–4 mg O2 L−1 ). Although the total nitrogen removal rates showed potential, the accumulation of nitrite and nitrate resulted in lower nitrogen removal efficiencies (around 40 %), which should be improved in the future. Moreover, a balance should be found in the future between the increased NO and N2 O emissions and a decreased energy consumption to justify OLAND mainstream treatment. [ABSTRACT FROM AUTHOR]- Published
- 2013
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8. Repeated pulse feeding induces functional stability in anaerobic digestion.
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De Vrieze, Jo, Verstraete, Willy, and Boon, Nico
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ANAEROBIC digestion ,GREEN technology ,MICROBIAL diversity ,BIOGAS production ,AMMONIUM ,RENEWABLE energy sources ,ORGANIC wastes - Abstract
Anaerobic digestion is an environmental key technology in the future bio-based economy. To achieve functional stability, a minimal microbial community diversity is required. This microbial community should also have a certain 'elasticity', i.e. the ability to rapidly adapt to suboptimal conditions or stress. In this study it was evaluated whether a higher degree of functional stability could be achieved by changing the feeding pattern, which can change the evenness, dynamics and richness of the bacterial community. The first reactor ( CSTR
stable ) was fed on daily basis, whereas the second reactor ( CSTRdynamic ) was fed every 2 days. Average biogas production was 0.30 l CH4 l−1 day−1 in both reactors, although daily variation was up to four times higher in the CSTRdynamic compared with the CSTRstable during the first 50 days. Bacterial analysis revealed that this CSTRdynamic had a two times higher degree of bacterial community dynamics. The CSTRdynamic also appeared to be more tolerant to an organic shock load of 8 g COD l−1 and ammonium levels up to 8000 mg TAN l−1 . These results suggest that the regular application of a limited pulse of organic material and/or a variation in the substrate composition might promote higher functional stability in anaerobic digestion. [ABSTRACT FROM AUTHOR]- Published
- 2013
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9. Anaerobic digestibility of Scenedesmus obliquus and Phaeodactylum tricornutum under mesophilic and thermophilic conditions
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Zamalloa, Carlos, Boon, Nico, and Verstraete, Willy
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ANAEROBIC microorganisms , *DIGESTION , *SCENEDESMUS obliquus , *DIATOMS , *THERMOPHILIC microorganisms , *BIOMASS , *BIOGAS , *METHANE , *VOLUMETRIC analysis - Abstract
Abstract: Two types of non-axenic algal cultures, one dominated by the freshwater microalgae Scenedesmus obliquus and the other by the marine microalgae Phaeodactylum tricornutum, were cultivated in two types of simple photobioreactor systems. The production rates, expressed on dry matter (DM) basis, were in the order of 0.12 and 0.18g DML−1 d−1 for S. obliquus and P. tricornutum respectively. The biogas potential of algal biomass was assessed by performing standardized batch digestion as well as digestion in a hybrid flow-through reactor (combining a sludge blanket and a carrier bed), the latter under mesophilic and thermophilic conditions. Biomethane potential assays revealed the ultimate methane yield (B 0) of P. tricornutum biomass to be about a factor of 1.5 higher than that of S. obliquus biomass, i.e. 0.36 and 0.24LCH4 g−1 volatile solids (VS) added respectively. For S. obliquus biomass, the hybrid flow-through reactor tests operated at volumetric organic loading rate (Bv) of 2.8gVSL−1 d−1 indicated low conversion efficiencies ranging between 26–31% at a hydraulic retention time (HRT) of 2.2days for mesophilic and thermophilic conditions respectively. When digesting P. tricornutum at a Bv of 1.9gVSL−1 d−1 at either mesophilic or thermophilic conditions and at an HRT of 2.2days, an overall conversion efficiency of about 50% was obtained. This work indicated that the hydrolysis of the algae cells is limiting the anaerobic processing of intensively grown S. obliquus and P. tricornutum biomass. [Copyright &y& Elsevier]
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- 2012
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10. Anaerobic digestibility of marine microalgae Phaeodactylum tricornutum in a lab-scale anaerobic membrane bioreactor.
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Zamalloa, Carlos, Vrieze, Jo, Boon, Nico, and Verstraete, Willy
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ANAEROBIC digestion ,MICROALGAE ,MARINE microbiology ,BIOLOGICAL membranes ,BIOREACTOR research ,BIOGAS - Abstract
The biomass of industrially grown Phaeodactylum tricornutum was subjected in a novel way to bio-methanation at 33°C, i.e., in an anaerobic membrane bioreactor (AnMBR) at a hydraulic retention time of 2.5 days, at solid retention times of 20 to 10 days and at loading rates in the range of 2.6-5.9 g biomass-COD L day with membrane fluxes ranging from 1 to 0.8 L m h. The total COD recovered as biogas was in the order of 52%. The input suspension was converted to a clear effluent rich in total ammonium nitrogen (546 mg TAN L) and phosphate (141 mg PO-P L) usable as liquid fertilizer. The microbial community richness, dynamics, and organization in the reactor were interpreted using the microbial resource management approach. The AnMBR communities were found to be moderate in species richness and low in dynamics and community organization relative to UASB and conventional CSTR sludges. Quantitative polymerase chain reaction analysis revealed that Methanosaeta sp. was the dominant acetoclastic methanogen species followed by Methanosarcina sp. This work demonstrated that the use of AnMBR for the digestion of algal biomass is possible. The fact that some 50% of the organic matter is not liquefied means that the algal particulates in the digestate constitute a considerable fraction which should be valorized properly, for instance as slow release organic fertilizer. Overall, 1 kg of algae dry matter (DM) could be valorized in the form of biogas (€2.07), N and P in the effluent (€0.02) and N and P in the digestate (€0.04), thus totaling about €2.13 per kilogram algae DM. [ABSTRACT FROM AUTHOR]
- Published
- 2012
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11. Methanosarcina: The rediscovered methanogen for heavy duty biomethanation
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De Vrieze, Jo, Hennebel, Tom, Boon, Nico, and Verstraete, Willy
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METHANOSARCINA , *METHANATION , *ANAEROBIC digestion , *METHANOGENS , *RENEWABLE energy sources , *PERTURBATION theory , *ENVIRONMENTAL engineering , *AMMONIUM - Abstract
Abstract: Anaerobic digestion is an important technology in the framework of renewable energy production. The anaerobic digestion system is susceptible to perturbations due to the sensitivity of the methanogens towards environmental factors. Currently, technology is evolving from conventional waste treatment, i.e. the removal of pollutants, to very intensive biogas production from concentrated wastes, in the framework of bio-energy production. In the latter configuration Methanosarcina species appear to be of crucial importance. Methanosarcina sp. are, compared to other methanogens, quite robust towards different impairments. They are reported to be tolerant to total ammonium concentrations up to 7000mgL−1, salt concentrations up to 18,000mgNa+ L−1, a pH shock of 0.8–1.0 units and acetate concentrations up to 15,000mgCODL−1. The possibilities of Methanosarcina sp. as key organisms in specific types of anaerobic digestion systems are demonstrated in this review. [Copyright &y& Elsevier]
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- 2012
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12. Inactivation of Murine Norovirus 1 and Bacteroides fragilis Phage B40-8 by Mesophilic and Thermophilic Anaerobic Digestion of Pig Slurry.
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Baert, Leen, De Gusseme, Bart, Boon, Nico, Verstraete, Willy, Debevere, Johan, and Uyttendaele, Mieke
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GASTROENTERITIS , *ANAEROBIC digestion , *FERTILIZER research , *FERTILIZER manufacturing , *BACTEROIDES , *NOROVIRUSES , *ENTEROCOCCUS faecalis , *PATHOGENICITY of enteroviruses , *FOOD pasteurization , *DISEASE risk factors - Abstract
Mesophilic (37°C) and thermophilic (52°C) anaerobic digestion of pig slurry induced at least a 4-log decrease in murine norovirus 1, used as a surrogate virus for porcine norovirus, after 13 and 7 days, respectively. Bacteroides fragilis phage B40-8, employed as a universal viral model, was lowered by 2.5 log after 7 days. The viral titer declined due to temperature and matrix effects. [ABSTRACT FROM AUTHOR]
- Published
- 2010
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13. Microbial community redundancy in anaerobic digestion drives process recovery after salinity exposure.
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De Vrieze, Jo, Christiaens, Marlies E.R., Walraedt, Diego, Devooght, Arno, Ijaz, Umer Zeeshan, and Boon, Nico
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ANAEROBIC digestion , *AQUATIC microbiology , *ACTIVATED sludge process , *EFFECT of salt on bacteria , *FATTY acids - Abstract
Anaerobic digestion of high-salinity wastewaters often results in process inhibition due to the susceptibility of the methanogenic archaea. The ability of the microbial community to deal with increased salinity levels is of high importance to ensure process perseverance or recovery after failure. The exact strategy of the microbial community to ensure process endurance is, however, often unknown. In this study, we investigated how the microbial community is able to recover process performance following a disturbance through the application of high-salinity molasses wastewater. After a stable start-up, methane production quickly decreased from 625 ± 17 to 232 ± 35 mL CH 4 L −1 d −1 with a simultaneous accumulation in volatile fatty acids up to 20.5 ± 1.4 g COD L −1 , indicating severe process disturbance. A shift in feedstock from molasses wastewater to waste activated sludge resulted in complete process recovery. However, the bacterial and archaeal communities did not return to their original composition as before the disturbance, despite similar process conditions. Microbial community diversity was recovered to similar levels as before disturbance, which indicates that the metabolic potential of the community was maintained. A mild increase in ammonia concentration after process recovery did not influence methane production, indicating a well-balanced microbial community. Hence, given the change in community composition following recovery after salinity disturbance, it can be assumed that microbial community redundancy was the major strategy to ensure the continuation of methane production, without loss of functionality or metabolic flexibility. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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14. The full-scale anaerobic digestion microbiome is represented by specific marker populations.
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De Vrieze, Jo, Raport, Linde, Roume, Hugo, Vilchez-Vargas, Ramiro, Jáuregui, Ruy, Pieper, Dietmar H., and Boon, Nico
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WATER purification , *ANAEROBIC digestion , *WATER treatment plants , *AQUATIC microbiology , *ORGANIC wastes , *BIOGAS ,ENVIRONMENTAL aspects - Abstract
Anaerobic digestion is a well-established microbial-based technology for the treatment of organic waste streams and subsequent biogas recovery. A robust and versatile microbial community to ensure overall stability of the process is essential. Four full-scale anaerobic digestion plants were followed for one year to link operational characteristics with microbial community composition and structure. Similarities between digesters, community dynamics and co-occurrence between bacteria and archaea within each digester were analysed. Free ammonia concentration (>200 mg N L −1 ) and conductivity (>30 mS cm −1 ) hindered acetoclastic methanogenesis by Methanosaetaceae. Thus, methanogenesis was pushed to the hydrogenotrophic pathway carried out by Methanobacteriales and Methanomicrobiales. Firmicutes dominated the overall bacterial community in each of the digesters (>50%), however, principal coordinate analysis of Bray-Curtis indices showed that each of the four digesters hosted a unique microbial community. The uniqueness of this community was related to two phylotypes belonging to the Syntrophomonas genus (Phy32 and Phy34) and to one unclassified bacterium (Phy2), which could both be considered marker populations in the community. A clear differentiation in co-occurrence of methanogens with several bacteria was observed between the different digesters. Our results demonstrated that full-scale anaerobic digestion plants show constant dynamics and co-occurrence patterns in function of time, but are unique in terms of composition, related to the presence of marker populations. [ABSTRACT FROM AUTHOR]
- Published
- 2016
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15. Ammonia and temperature determine potential clustering in the anaerobic digestion microbiome.
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De Vrieze, Jo, Saunders, Aaron Marc, He, Ying, Fang, Jing, Nielsen, Per Halkjaer, Verstraete, Willy, and Boon, Nico
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AMMONIA , *TEMPERATURE effect , *ANAEROBIC digestion , *ENVIRONMENTAL impact analysis , *REVERSE transcriptase polymerase chain reaction - Abstract
Anaerobic digestion is regarded as a key environmental technology in the present and future bio-based economy. The microbial community completing the anaerobic digestion process is considered complex, and several attempts already have been carried out to determine the key microbial populations. However, the key differences in the anaerobic digestion microbiomes, and the environmental/process parameters that drive these differences, remain poorly understood. In this research, we hypothesized that differences in operational parameters lead to a particular composition and organization of microbial communities in full-scale installations. A total of 38 samples were collected from 29 different full-scale anaerobic digestion installations, showing constant biogas production in function of time. Microbial community analysis was carried out by means of amplicon sequencing and real-time PCR. The bacterial community in all samples was dominated by representatives of the Firmicutes, Bacteroidetes and Proteobacteria, covering 86.1 ± 10.7% of the total bacterial community. Acetoclastic methanogenesis was dominated by Methanosaetaceae, yet, only the hydrogenotrophic Methanobacteriales correlated with biogas production, confirming their importance in high-rate anaerobic digestion systems. In-depth analysis of operational and environmental parameters and bacterial community structure indicated the presence of three potential clusters in anaerobic digestion. These clusters were determined by total ammonia concentration, free ammonia concentration and temperature, and characterized by an increased relative abundance of Bacteroidales, Clostridiales and Lactobacillales, respectively. None of the methanogenic populations, however, could be significantly attributed to any of the three clusters. Nonetheless, further experimental research will be required to validate the existence of these different clusters, and to which extent the presence of these clusters relates to stable or sub-optimal anaerobic digestion. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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16. Co-digestion of molasses or kitchen waste with high-rate activated sludge results in a diverse microbial community with stable methane production.
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De Vrieze, Jo, Plovie, Kristof, Verstraete, Willy, and Boon, Nico
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FARM manure in methane production , *BIOCHEMICAL substrates , *METHANOBACTERIACEAE , *SEWAGE sludge , *BIOGAS - Abstract
Kitchen waste and molasses are organic waste streams with high organic content, and therefore are interesting substrates for renewable energy production by means of anaerobic digestion. Both substrates, however, often cause inhibition of the anaerobic digestion process, when treated separately, hence, co-digestion with other substrates is required to ensure stable methane production. In this research, A-sludge (sludge harvested from a high rate activated sludge system) was used to stabilize co-digestion with kitchen waste or molasses. Lab-scale digesters were fed with A-sludge and kitchen waste or molasses for a total period of 105 days. Increased methane production values revealed a stabilizing effect of concentrated A-sludge on kitchen waste digestion. Co-digestion of molasses with A-sludge also resulted in a higher methane production. Volumetric methane production rates up to 1.53 L L −1 d −1 for kitchen waste and 1.01 L L −1 d −1 for molasses were obtained by co-digestion with A-sludge. The stabilizing effect of A-sludge was attributed to its capacity to supplement various nutrients. Microbial community results demonstrated that both reactor conditions and substrate composition determined the nature of the bacterial community, although there was no direct influence of micro-organisms in the substrate itself, while the methanogenic community profile remained constant as long as optimal conditions were maintained. [ABSTRACT FROM AUTHOR]
- Published
- 2015
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17. Anaerobic digestion of molasses by means of a vibrating and non-vibrating submerged anaerobic membrane bioreactor.
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De Vrieze, Jo, Hennebel, Tom, Van den Brande, Jens, Bilad, Ro'il M., Bruton, Thomas A., Vankelecom, Ivo F.J., Verstraete, Willy, and Boon, Nico
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ANAEROBIC digestion , *MOLASSES , *BIOREACTORS , *FATTY acids , *VOLATILE organic compounds , *METHANOBACTERIACEAE , *WASTE treatment - Abstract
Bio-refineries produce large volumes of waste streams with high organic content, which are potentially interesting for further processing. Anaerobic digestion (AD) can be a key technology for treatment of these sidestreams, such as molasses. However, the high concentration of salts in molasses can cause inhibition of methanogenesis. In this research, concentrated and diluted molasses were subjected to biomethanation in two types of submerged anaerobic membrane bioreactors (AnMBRs): one with biogas recirculation and one with a vibrating membrane. Both reactors were compared in terms of methane production and membrane fouling. Biogas recirculation seemed to be a good way to avoid membrane fouling, while the trans membrane pressures in the vibrating MBR increased over time, due to cake layer formation and the absence of a mixing system. Stable methane production, up to 2.05 L L−1 d−1 and a concomitant COD removal of 94.4%, was obtained only when diluted molasses were used, since concentrated molasses caused a decrease in methane production and an increase in volatile fatty acids (VFA), indicating an inhibiting effect of concentrated molasses on AD. Real-time PCR results revealed a clear dominance of Methanosaetaceae over Methanosarcinaceae as the main acetoclastic methanogens in both AnMBRs. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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18. Biomass retention on electrodes rather than electrical current enhances stability in anaerobic digestion.
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De Vrieze, Jo, Gildemyn, Sylvia, Arends, Jan B.A., Vanwonterghem, Inka, Verbeken, Kim, Boon, Nico, Verstraete, Willy, Tyson, Gene W., Hennebel, Tom, and Rabaey, Korneel
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BIOMASS , *ELECTRODES , *ELECTRIC currents , *ANAEROBIC digestion , *WASTE products as fuel , *BIOELECTROCHEMISTRY - Abstract
Abstract: Anaerobic digestion (AD) is a well-established technology for energy recovery from organic waste streams. Several studies noted that inserting a bioelectrochemical system (BES) inside an anaerobic digester can increase biogas output, however the mechanism behind this was not explored and primary controls were not executed. Here, we evaluated whether a BES could stabilize AD of molasses. Lab-scale digesters were operated in the presence or absence of electrodes, in open (no applied potential) and closed circuit conditions. In the control reactors without electrodes methane production decreased to 50% of the initial rate, while it remained stable in the reactors with electrodes, indicating a stabilizing effect. After 91 days of operation, the now colonized electrodes were introduced in the failing AD reactors to evaluate their remediating capacity. This resulted in an immediate increase in CH4 production and VFA removal. Although a current was generated in the BES operated in closed circuit, no direct effect of applied potential nor current was observed. A high abundance of Methanosaeta was detected on the electrodes, however irrespective of the applied cell potential. This study demonstrated that, in addition to other studies reporting only an increase in methane production, a BES can also remediate AD systems that exhibited process failure. However, the lack of difference between current driven and open circuit systems indicates that the key impact is through biomass retention, rather than electrochemical interaction with the electrodes. [Copyright &y& Elsevier]
- Published
- 2014
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19. High-rate iron-rich activated sludge as stabilizing agent for the anaerobic digestion of kitchen waste.
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De Vrieze, Jo, De Lathouwer, Lars, Verstraete, Willy, and Boon, Nico
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ACTIVATED sludge process , *ANAEROBIC digestion , *IRON in water , *SUBSTRATES (Materials science) , *ORGANIC compounds , *FOOD industrial waste - Abstract
Abstract: Anaerobic digestion is a key technology in the bio-based economy and can be applied to convert a wide range of organic substrates into CH4 and CO2. Kitchen waste is a valuable substrate for anaerobic digestion, since it is an abundant source of organic matter. Yet, digestion of single kitchen waste often results in process failure. High-rate activated sludge or A-sludge is produced during the highly loaded first stage of the two-phase ‘Adsorptions-Belebungsverfahren’ or A/B activated sludge system for municipal wastewater treatment. In this specific case, the A-sludge was amended with FeSO4 to enhance phosphorous removal and coagulation during the water treatment step. This study therefore evaluated whether this Fe-rich A-sludge could be used to obtain stable methanation and higher methane production values during co-digestion with kitchen waste. It was revealed that Fe-rich A-sludge can be a suitable co-substrate for kitchen waste; i.e. methane production rate values of 1.15 ± 0.22 and 1.12 ± 0.28 L L−1 d−1 were obtained during mesophilic and thermophilic co-digestion respectively of a feed-mixture consisting of 15% KW and 85% A-sludge. The thermophilic process led to higher residual VFA concentrations, up to 2070 mg COD L−1, and can therefore be considered less stable. Addition of micro- and macronutrients provided a more stable digestion of single kitchen waste, i.e. a methane production of 0.45 L L−1 d−1 was obtained in the micronutrient treatment compared to 0.30 L L−1 d−1 in the control treatment on day 61. Yet, methane production during single kitchen waste digestion still decreased toward the end of the experiment, despite the addition of micronutrients. Methane production rates were clearly influenced by the total numbers of archaea in the different reactors. This study showed that Fe-rich A-sludge and kitchen waste are suitable for co-digestion. [Copyright &y& Elsevier]
- Published
- 2013
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20. Electrochemical Resource Recovery from Digestate to Prevent Ammonia Toxicity during Anaerobic Digestion.
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Desloover, Joachim, Woldeyohannis, Andualem Abate, Verstraete, Willy, Boon, Nico, and Rabaey, Korneel
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AMMONIA poisoning , *ANAEROBIC digestion , *WASTE recycling , *RESEARCH methodology , *ELECTRIC batteries , *FLUX (Energy) , *CHARGE transfer kinetics - Abstract
Ammonia inhibition during anaerobic digestion limits the substrate loading rate and endangers process stability. Furthermore, digestates are interesting feedstocks for nutrient recovery. In this lab-scale study, an electrochemical cell was used to investigate the NH2+ flux from anode to cathode. Under optimal conditions with synthetic wastewater, an NH2+ charge transfer efficiency of 96% and NH2+ flux of 120 g N m-2 d-1 could be obtained at a concomitant electricity input of 5 kWh kg-1 N removed. A more selective NH2+ transfer could be established by maintaining a high concentration of other cations in the cathode compartment. Comparable NH2+ fluxes could be obtained with digestate at an electrical power input of 13 kWh kg-1 N removed and 41% current efficiency. The ammonium level in the digestate could be lowered from 2.1 to 0.8 - 1.2 g N L-1. Interestingly, also potassium fluxes of up to 241 g K+ m-2 d-1 could be obtained at 23% current efficiency. As the cathode can be operated at high pH without the need for chemical addition, stripping and absorption of dissolved ammonia could reach 100% efficiency. By valorization of the generated side products, this technology shows economic potential for practical application. [ABSTRACT FROM AUTHOR]
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- 2012
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21. Triangulation of microbial fingerprinting in anaerobic digestion reveals consistent fingerprinting profiles.
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De Vrieze, Jo, Heyer, Robert, Props, Ruben, Van Meulebroek, Lieven, Gille, Karen, Vanhaecke, Lynn, Benndorf, Dirk, and Boon, Nico
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ANAEROBIC capacity , *ANAEROBIC digestion , *TRIANGULATION , *MICROBIAL communities , *FLOW cytometry - Abstract
• Triangulation of fingerprinting methods reveals similar separation of digesters • Combining of fingerprinting features does not improve clustering of digesters • Identification of features is not always consistent between methods • Cytometric fingerprinting is reliable for anaerobic digestion microbiome monitoring The anaerobic digestion microbiome has been puzzling us since the dawn of molecular methods for mixed microbial community analysis. Monitoring of the anaerobic digestion microbiome can either take place via a non-targeted holistic evaluation of the microbial community through fingerprinting or by targeted monitoring of selected taxa. Here, we compared four different microbial community fingerprinting methods, i.e. , amplicon sequencing, metaproteomics, metabolomics and cytomics, in their ability to characterise the full-scale anaerobic digestion microbiome. Cytometric fingerprinting through cytomics reflects a, for anaerobic digestion, novel, single cell-based approach of direct microbial community fingerprinting by flow cytometry. Three different digester types, i.e. , sludge digesters, digesters treating agro-industrial waste and dry anaerobic digesters, each reflected different operational parameters. The α-diversity analysis yielded inconsistent results, especially for richness, across the different methods. In contrast, β-diversity analysis resulted in comparable profiles, even when translated into phyla or functions, with clear separation of the three digester types. In-depth analysis of each method's features i.e. , operational taxonomic units, metaproteins, metabolites, and cytometric traits, yielded certain similar features, yet, also some clear differences between the different methods, which was related to the complexity of the anaerobic digestion process. In conclusion, cytometric fingerprinting through flow cytometry is a reliable, fast method for holistic monitoring of the anaerobic digestion microbiome, and the complementary identification of key features through other methods could give rise to a direct interpretation of anaerobic digestion process performance. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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22. Adaptation and characterization of thermophilic anammox in bioreactors.
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Vandekerckhove, Tom G.L., Props, Ruben, Carvajal-Arroyo, José M., Boon, Nico, and Vlaeminck, Siegfried E.
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WATER treatment plant residuals , *NITROGEN cycle , *NITROGEN removal (Sewage purification) , *SEWAGE sludge digestion , *THERMOPHILIC bacteria , *ANAEROBIC digestion , *BACTERIAL communities , *PHYSIOLOGICAL adaptation - Abstract
Anammox, the oxidation of ammonium with nitrite, is a key microbial process in the nitrogen cycle. Under mesophilic conditions (below 40 °C), it is widely implemented to remove nitrogen from wastewaters lacking organic carbon. Despite evidence of the presence of anammox bacteria in high-temperature environments, reports on the cultivation of thermophilic anammox bacteria are limited to a short-term experiment of 2 weeks. This study showcases the adaptation of a mesophilic inoculum to thermophilic conditions, and its characterization. First, an attached growth technology was chosen to obtain the process. In an anoxic fixed-bed biofilm bioreactor (FBBR), a slow linear temperature increase from 38 to over 48 °C (0.05–0.07 °C d−1) was imposed to the community over 220 days, after which the reactor was operated at 48 °C for over 200 days. Maximum total nitrogen removal rates reached up to 0.62 g N L−1 d−1. Given this promising performance, a suspended growth system was tested. The obtained enrichment culture served as inoculum for membrane bioreactors (MBR) operated at 50 °C, reaching a maximum total nitrogen removal rate of 1.7 g N L−1 d−1 after 35 days. The biomass in the MBR had a maximum specific anammox activity of 1.1 ± 0.1 g NH 4 +-N g−1 VSS d−1, and the growth rate was estimated at 0.075–0.19 d−1. The thermophilic cultures displayed nitrogen stoichiometry ratios typical for mesophilic anammox: 0.93–1.42 g NO 2 --N removed g−1 NH 4 +-N removed and 0.16–0.35 g NO 3 --N produced g−1 NH 4 +-N removed. Amplicon and Sanger sequencing of the 16S rRNA genes revealed a disappearance of the original "Ca. Brocadia" and "Ca. Jettenia" taxa, yielding Planctomycetes members with only 94–95% similarity to "Ca. Brocadia anammoxidans" and "Ca. B. caroliniensis", accounting for 45% of the bacterial FBBR community. The long-term operation of thermophilic anammox reactors and snapshot views on the nitrogen stoichiometry, kinetics and microbial community open up the development path of thermophilic partial nitritation/anammox. A first economic assessment highlighted that treatment of sludge reject water from thermophilic anaerobic digestion of sewage sludge may become attractive. Image 1 • A slow temperature increase on a mesophilic inoculum enabled thermophilic anammox. • A potentially novel species was highly abundant in the adapted community. • Stoichiometry and rescaled kinetics are low compared to mesophilic anammox cultures. • An attached and a suspended growth reactor were feasible. • Thermophilic partial nitritation/anammox may become economically cost-effective. [ABSTRACT FROM AUTHOR]
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- 2020
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23. Methanosaeta vs. Methanosarcina in anaerobic digestion: the quest for enhanced biogas production
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De Vrieze, Jo, Boon, Nico, and Verstraete, Willy
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anaerobic digestion ,Earth and Environmental Sciences ,Methanosarcina ,environmental microbiology ,biogas ,methanogenesis ,Methanosaeta ,microbbial ecology - Abstract
The production of renewable energy from organic waste streams is one of the most important aspects in the concept of sustainable development. Anaerobic digestion can be considered one of the main techniques to treat organic waste streams, allowing both waste stabilization and renewable energy production in the form of biogas. Its widespread application on full-scale relates to the fact that anaerobic digestion has, apart from biogas production and organic waste stabilization, several other advantages over alternative biological processes, e.g. a low cell yield, a high organic loading rate, limited nutrient demands, and low costs for operation and maintenance of the reactor system. The methanogenic archaea are responsible for the final and critical step of anaerobic digestion, as they produce valuable methane. One of the major drawbacks of anaerobic digestion is, however, the sensitivity of the methanogenic community to different environmental factors or stressors. At this point, our knowledge of the microbial community taking care of the different stages in anaerobic digestion is still limited and, therefore, anaerobic digestion can still be considered a ‘black box’. Indeed, our knowledge of the bacterial community is restricted to the attribution of the first three steps in anaerobic digestion, i.e. hydrolysis, acidogenesis and acetogenesis. Although several key populations have already been identified, the exact contribution of the different bacterial phyla remains, however, to be elucidated. Methanogenesis, the last step, is carried out by archaea. The methanogenic community can be divided into two different groups, related to their main methanogenic pathway, i.e. hydrogenotrophic and acetoclastic methanogens. Thus far, only two genera, Methanosaeta and Methanosarcina, are reported to be able to carry out acetoclastic methanogenesis. Due to a distinct difference in physiology, morphology and metabolic potential, these two genera are expected to occupy different niches in anaerobic digestion. However, up until now, little is known about the specific contribution of both genera to methanogenesis in anaerobic digestion. The main objective of this research was to unravel the ‘black box’ of anaerobic digestion to allow better and more solid process engineering. Several strategies were applied to improve biogas production and process stability, by (in)directly influencing the microbial community. A main focus was placed on the methanogenic community, as methanogenesis can be considered the weak link in the chain, because of the sensitivity of the methanogenic community to different environmental factors. However, to reach stable methane production, a close interaction between the bacterial and methanogenic community is required, hence, the bacterial community was also examined in terms of composition and organization. In Chapter 2, A-sludge originating from the A-stage of the ‘Adsorptions-Belebungsverfahren’, was co-digested with kitchen waste to increase biogas production. This Fe-rich A-sludge appeared to be a suitable co-substrate for kitchen waste, as methane production rate values of 1.15 ± 0.22 and 1.12 ± 0.28 L L-1 d-1 were obtained during mesophilic and thermophilic co-digestion, respectively, of a feed-mixture consisting of 15% kitchen waste and 85% A-sludge. Mono-digestion of kitchen waste resulted in process failure. The thermophilic process led to higher residual volatile fatty acid concentrations, up to 2070 mg COD L-1, hence, the mesophilic process can be considered the most ‘stable’. The optimal combination of A-sludge and kitchen waste served as a basis for the co-digestion of A-sludge with kitchen waste or molasses at mesophilic conditions in Chapter 3. In this chapter the objective was to evaluate the exact stabilizing mechanism of A-sludge as co-substrate in anaerobic digestion. Co-digestion of kitchen waste and molasses with A-sludge resulted in stable methane production, as values up to 1.53 L L-1 d-1 for kitchen waste and 1.01 L L-1 d-1 for molasses were obtained. The stabilizing effect of A-sludge in anaerobic digestion could not be attributed to bioaugmentation, despite its indigenous methanogenic activity, and therefore was dominated by nutrient addition. Methanosaetaceae maintained high copy numbers, between 109 and 1010 copies g-1 sludge, as long as optimal conditions were maintained, irrespective of the selected (co-)substrates. However, an increase in volatile fatty acids and a decrease in pH resulted in a decreased abundance of Methanosaetaceae. In Chapter 4, a different feeding pattern was applied to obtain a higher degree of functional stability by (in)directly changing the evenness, dynamics and richness of the bacterial community. A short-term stress test revealed that pulse feeding leads to a higher tolerance of the digester to an organic shock load of 8 g COD L-1 and total ammonia levels up to 8000 mg N L-1. The bacterial community showed a high degree of dynamics over time, yet the methanogenic community remained constant. These results suggest that the regular application of a limited pulse of organic material and/or a variation in the substrate composition might promote higher functional stability in anaerobic digestion. In Chapter 2-4, the anaerobic sludge originating from the same sludge digester was used as inoculum. The contribution of the inoculum to stable methane production and stress tolerance was investigated in Chapter 5. A different response in terms of start-up efficiency and ammonium tolerance was observed between the different inocula. Methanosaeta was the dominant acetoclastic methanogen, yet Methanosarcina increased in abundance at elevated ammonium concentrations. A shift from a Firmicutes to a Proteobacteria dominated bacterial community was observed in failing digesters. Methane production was strongly positively correlated with Methanosaetaceae, but with several bacterial populations as well. Overall, these results indicated the importance of inoculum selection to ensure stable operation and stress tolerance in anaerobic digestion. In several studies, the positive effect of a bioelectrochemical system on biogas production in anaerobic digestion is described, however, the main mechanism behind this remained unsolicited, and primary controls were not executed. In Chapter 6, the stabilizing ability of a bioelectrochemical system for molasses digestion was evaluated in a 154 days experiment. A high abundance of Methanosaeta was detected on the electrodes, however, irrespective of the applied cell potential. This study demonstrated that, in addition to other studies reporting only an increase in methane production, a bioelectrochemical system can also remediate anaerobic digestion systems that exhibited process failure. However, the lack of difference between current driven and open circuit systems indicates that the key impact is through biomass retention, especially Methanosaetaceae, rather than electrochemical interaction with the electrodes. Anaerobic membrane bioreactors with different fouling prevention strategies, i.e. biogas recirculation or membrane vibration, were applied to increase the retention of slow growing methanogens in Chapter 7. Biogas recirculation was the best mechanism to avoid membrane fouling, while the trans membrane pressures in the vibrating membrane bioreactor increased over time, due to cake layer formation. Stable methane production, up to 2.05 L L-1 d-1 and a concomitant COD removal of 94.4%, were obtained, only when diluted molasses were used, since concentrated molasses resulted in process failure. Real-time PCR results revealed a clear dominance of Methanosaetaceae over Methanosarcinaceae as the main acetoclastic methanogens in both anaerobic membrane bioreactor systems. In Chapter 8, an extensive evaluation of 38 samples from 29 full-scale anaerobic digestion plants was carried out to relate operational parameters to microbial community composition and organization. The bacterial community was dominated by representatives of the Firmicutes, Bacteroidetes and Proteobacteria, covering 86.1 ± 10.7% of the total bacterial community. Acetoclastic methanogenesis was dominated by Methanosaetaceae, yet, only Methanobacteriales significantly positively correlated to biogas production. Three potential clusters, that could be considered as ‘AD-types’, were identified. These so-called ‘AD-types’ were determined by total ammonia concentration, free ammonia concentration and temperature, and characterized by an increased abundance of the Bacteroidales, Clostridiales and Lactobacillales, respectively. The identification of these three potential AD-types may serve as a basis for directly engineering the microbial community in anaerobic digestion. However, further research will be required to validated the actual existence of these three clusters in AD. This research demonstrated the potential of several operational and technological strategies to improve biogas production and process stability in anaerobic digestion. Stable anaerobic digestion hosts a static methanogenic community, as long as evolving operational parameters or substrate composition do not influence the optimal conditions for methanogenesis, and an ever dynamic bacterial community. Methanosaetaceae are the uncontested dominant methanogens in anaerobic digestion, irrespective of the substrate, operational conditions or reactor configuration. However, increasing ammonium, salt and volatile fatty acid concentrations cause a shift from acetoclastic methanogenesis by Methanosaetaceae to hydrogenotrophic methanogenesis. Comparison of the lab-scale reactor results with full-scale plant microbial community analysis results showed a high similarity on bacterial level. However, at ‘deteriorating’ conditions at lab-scale a transition to a Methanosarcinaceae dominated methanogenesis was observed, while this shift could not be observed in full-scale plants. Hence, instead of Methanosarcinaceae, the Methanobacteriales are to be considered as the main drivers of so-called high-rate anaerobic digestion. The identification of the three AD-types can serve as a basis for unravelling the anaerobic digestion microbiome. Further in-depth research, however, will be required to determine the exact role of the core micro-organisms in each cluster to allow microbial community based engineering of anaerobic digestion ecosystems. The application of RNA, protein and metabolite based methods will be essential to estimate the effective metabolic activity of the microbial community in anaerobic digestion, thus, allowing more in-depth process control and further unravelling of the anaerobic digestion ‘black box’.
- Published
- 2014
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