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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    Wirelessly powered ultraviolet light emitting diodes for photocatalytic oxidation
    Kuipers, J. ; Bruning, H. ; Yntema, D.R. ; Rijnaarts, H.H.M. - \ 2015
    Journal of Photochemistry and Photobiology. A, Chemistry 299 (2015). - ISSN 1010-6030 - p. 25 - 30.
    heterogeneous photocatalysis - water-treatment - reactor - design - pollutants - systems
    A method is presented to distribute small scale light sources in a photocatalytic slurry reactor. The goal of distributing the light sources is to increase photon transfer efficiency, and thereby increasing the reaction rate, compared to using one single light source. The light sources used in this study were ultraviolet light emitting diodes with a wavelength of 375 nm. An up-flow of air into the photocatalytic reactor distributes the UV-LEDs throughout the reactor, mixes the reaction solution and saturates the solution with molecular oxygen. To make distribution of the UV-LEDs possible, the UV-LEDs were powered wirelessly by resonant inductive coupling. This article shows that UV-LEDs distributed throughout the reactor show a 30% higher removal rate of methylene blue compared to the UV-LEDs concentrated on one plane in the reactor. The removal rate increased linearly with increasing numbers of UV-LEDs. The size of the UV-LEDs determined that up to 32 UV-LEDs could be wirelessly powered in a reactor volume of 500 ml. To increase the reactivity, a higher amount of UV-LEDs per reaction liquid volume and higher radiant power of the UV-LED can be used, bringing use of photocatalytic reactors closer to industrial applications.
    High specific activity for anammox bacteria enriched from activated sludge at 10 °C
    Hendrickx, T.L.G. ; Kampman, C. ; Zeeman, G. ; Temmink, B.G. ; Hu, Z. ; Kartal, B. ; Buisman, C.J.N. - \ 2014
    Bioresource Technology 163 (2014). - ISSN 0960-8524 - p. 214 - 221.
    anaerobic ammonium oxidation - autotrophic nitrogen removal - strength waste-water - low-temperature - granular sludge - marine-sediments - performance - sewage - scale - reactor
    Anammox in the water line of a waste water treatment plant (WWTP) saves energy for aeration and allows for recovering biogas from organic material. Main challenges for applying the anammox process in the water line are related to the low temperature of
    CO2 capture by biomimetic adsorption: enzyme mediated co2 absorption for post-combustion carbon sequestration and storage process
    Russo, M.E. ; Olivieri, G. ; Salatino, P. ; Marzocchella, A. - \ 2013
    Environmental Engineering and Management Journal (EEMJ) 12 (2013)8. - ISSN 1582-9596 - p. 1595 - 1601.
    butanol production - inhibitor removal - mass-transfer - anhydrase ii - hydration - kinetics - dioxide - reactor - microreactor - diffusivity
    The huge emission of greenhouse gases from fossil-fuelled power plants is emphasizing the need for efficient Carbon Capture and Storage (CCS) technologies. The biomimetic CO2 absorption in aqueous solutions has been recently investigated as a promising innovative alternative for post-combustion CCS. The carbonic anhydrase (CA) - a broad group of ubiquitous enzymes - may catalyse the CO2 hydration reaction and then to promote CO2 absorption rate into aqueous solutions. Nevertheless the research on this issue is quite active, the reliable designing of absorption units still requires more details. The present study proposes the design of a random packing absorption column operated with alkaline solvents supplied with CA. The height of the packed bed to fulfil the 80% of CO2 abatement from a flue gas stream was as large as 15-20 m. A comprehensive discussion of effects of operating conditions and of CA features on unit performance is reported.
    Chain elongation of acetate and ethanol in an upflow anaerobic filter for high rate MCFA production
    Grootscholten, T.I.M. ; Steinbusch, K.J.J. ; Hamelers, H.V.M. ; Buisman, C.J.N. - \ 2013
    Bioresource Technology 135 (2013). - ISSN 0960-8524 - p. 440 - 445.
    mixed cultures - liquid fuels - reactor - digestion - caproate - hydrogen - biomass - waste
    Recently, interest has regained for medium chain fatty acids (MCFAs) as a low cost feedstock for bio-based chemical and fuel production processes. To become cost-effective, the volumetric MCFA production rate by chain elongation should increase to comparable rates of other fermentation processes. We investigate the MCFA production process at a hydraulic retention time of 17 h in an upflow anaerobic filter to improve the volumetric MCFA production rate. This approach resulted in a MCFA production with a volumetric production rate of 16.6 g l-1 d-1, which is more than seven times higher than the current production rate. Moreover the rate is now in the range of other fermentation processes like methane, butanol and ethanol production. Increasing the ethanol load lead to higher volumetric production rates and a high MCFA selectivity of 91%. During operation, methane percentages lower than 0.1% were detected in the headspace of reactor.
    Enrichment of denitrifying methanotrophic bacteria for application after direct low-temperature anaerobic sewage treatment
    Kampman, C. ; Hendrickx, T.L.G. ; Luesken, F. ; Alen, T.A. ; Jetten, M.S.M. ; Camp, H.J.M. op den; Zeeman, G. ; Buisman, C.J.N. ; Temmink, B.G. - \ 2012
    Journal of Hazardous Materials 227-228 (2012). - ISSN 0304-3894 - p. 164 - 171.
    uasb-digester system - waste-water - ammonium oxidation - methane oxidation - denitrification - reactor
    Despite many advantages of anaerobic sewage treatment over conventional activated sludge treatment, it has not yet been applied in temperate zones. This is especially because effluent from low-temperature anaerobic treatment contains nitrogen and dissolved methane. The presence of nitrogen and methane offers the opportunity to develop a reactor in which methane is used as electron donor for denitrification. Such a reactor could be used in a new concept for low-temperature anaerobic sewage treatment, consisting of a UASB-digester system, a reactor for denitrification coupled to anaerobic methane oxidation, and a nitritation reactor. In the present study denitrifying methanotrophic bacteria similar to ‘Candidatus Methylomirabilis oxyfera’ were enriched. Maximum volumetric nitrite consumption rates were 33.5 mg NO2--N/L d (using synthetic medium) and 37.8 mg NO2--N/L d (using medium containing effluent from a sewage treatment plant), which are similar to the maximum rate reported so far. Though the goal was to increase the rates, in both reactors, after reaching these maximum rates, volumetric nitrite consumption rates decreased in time. Results indicate biomass washout may have significantly decelerated enrichment. Therefore, to obtain higher volumetric consumption rates, further research should focus on systems with complete biomass retention.
    Autotrophic nitrogen removal from low strength waste water at low temperature
    Hendrickx, T.L.G. ; Wang, Y. ; Kampman, C. ; Zeeman, G. ; Temmink, B.G. ; Buisman, C.J.N. - \ 2012
    Water Research 46 (2012)7. - ISSN 0043-1354 - p. 2187 - 2193.
    afvalwaterbehandeling - afvalwaterbehandelingsinstallaties - stikstof - verwijdering - denitrificatie - temperatuur - anaërobe behandeling - ammonium - oxidatie - energiebesparing - stedelijk afvalwater - waste water treatment - waste water treatment plants - nitrogen - removal - denitrification - temperature - anaerobic treatment - ammonium - oxidation - energy saving - municipal wastewater - anaerobic ammonium oxidation - treat sewage - reactor - system
    Direct anaerobic treatment of municipal waste waters allows for energy recovery in the form of biogas. A further decrease in the energy requirement for waste water treatment can be achieved by removing the ammonium in the anaerobic effluent with an autotrophic process, such as anammox. Until now, anammox has mainly been used for treating warm (>30 °C) and concentrated (>500 mg N/L) waste streams. Application in the water line of municipal waste water treatment poses the challenges of a lower nitrogen concentration (
    Pathways of sulfide oxidation by haloalkaliphilic bacteria in limited-oxygen gas lift bioreactors
    Klok, J.B. ; Bosch, P.L.F. van den; Buisman, C.J.N. ; Stams, A.J.M. ; Keesman, K.J. ; Janssen, A.J.H. - \ 2012
    Environmental Science and Technology 46 (2012)14. - ISSN 0013-936X - p. 7581 - 7586.
    sulfur-oxidizing bacteria - complete genome sequence - alkaline conditions - hydrogen-sulfide - soda lakes - mechanism - removal - reactor
    Physicochemical processes, such as the Lo-cat and Amine-Claus process, are commonly used to remove hydrogen sulfide from hydrocarbon gas streams such as landfill gas, natural gas, and synthesis gas. Biodesulfurization offers environmental advantages, but still requires optimization and more insight in the reaction pathways and kinetics. We carried out experiments with gas lift bioreactors inoculated with haloalkaliphilic sulfide-oxidizing bacteria. At oxygen-limiting levels, that is, below an O(2)/H(2)S mole ratio of 1, sulfide was oxidized to elemental sulfur and sulfate. We propose that the bacteria reduce NAD(+) without direct transfer of electrons to oxygen and that this is most likely the main route for oxidizing sulfide to elemental sulfur which is subsequently oxidized to sulfate in oxygen-limited bioreactors. We call this pathway the limited oxygen route (LOR). Biomass growth under these conditions is significantly lower than at higher oxygen levels. These findings emphasize the importance of accurate process control. This work also identifies a need for studies exploring similar pathways in other sulfide oxidizers such as Thiobacillus bacteria
    Diversity and enrichment of nitrite-dependent anaerobic methane oxidizing bacteria from wastewater sludge
    Luesken, F. ; Alen, T. van; Biezen, J. van der; Frijters, C. ; Toonen, G. ; Kampman, C. ; Hendrickx, T.L.G. ; Zeeman, G. ; Temmink, B.G. ; Strous, M. ; Camp, H.J.M. op den; Jetten, M.S.M. - \ 2011
    Applied Microbiology and Biotechnology (2011). - ISSN 0175-7598
    afvalwaterbehandeling - waterzuivering - anaërobe behandeling - methaan - oxidatie - bacteriën - nieuwe stam - denitrificerende micro-organismen - waste water treatment - water treatment - anaerobic treatment - methane - oxidation - bacteria - new phylum - denitrifying microorganisms - activated-sludge - microorganisms - populations - technology - reactor
    Recently discovered microorganisms affiliated to the bacterial phylum NC10, named “Candidatus Methylomirabilis oxyfera”, perform nitrite-dependent anaerobic methane oxidation. These microorganisms could be important players in a novel way of anaerobic wastewater treatment where ammonium and residual dissolved methane might be removed at the expense of nitrate or nitrite. To find suitable inocula for reactor startup, ten selected wastewater treatment plants (WWTPs) located in The Netherlands were screened for the endogenous presence of M. oxyfera using molecular diagnostic methods. We could identify NC10 bacteria with 98% similarity to M. oxyfera in nine out of ten WWTPs tested. Sludge from one selected WWTP was used to start a new enrichment culture of NC10 bacteria. This enrichment was monitored using specific pmoA primers and M. oxyfera cells were visualized with fluorescence oligonucleotide probes. After 112 days, the enrichment consumed up to 0.4 mM NO2- per day. The results of this study show that appropriate sources of biomass, enrichment strategies, and diagnostic tools existed to start and monitor pilot scale tests for the implementation of nitrite-dependent methane oxidation in wastewater treatment at ambient temperature
    Grey water biodegradability
    Abu Ghunmi, L. ; Zeeman, G. ; Fayyad, M. ; Lier, J.B. van - \ 2011
    Biodegradation 22 (2011). - ISSN 0923-9820 - p. 163 - 174.
    greywater treatment - microbial quality - reuse - technologies - operation - reactor
    Knowing the biodegradability characteristics of grey water constituents is imperative for a proper design and operation of a biological treatment system of grey water. This study characterizes the different COD fractions of dormitory grey water and investigates the effect of applying different conditions in the biodegradation test. The maximum aerobic and anaerobic biodegradability and conversion rate for the different COD fractions is determined. The results show that, on average, dormitory grey water COD fractions are 28% suspended, 32% colloidal and 40% dissolved. The studied factors incubation time, inoculum addition and temperature are influencing the determined biodegradability. The maximum biodegradability and biodegradation rate differ between different COD fractions, viz. CODss, CODcol and CODdiss. The dissolved COD fraction is characterised by the lowest degradation rate, both for anaerobic and aerobic conditions. The maximum biodegradability for aerobic and anaerobic conditions is 86 and 70% respectively, whereas the first order conversion rate constant, k20, is 0.119 and 0.005 day-1, respectively. The anaerobic and aerobic conversion rates in relation to temperature can be described by the Arrhenius relation, with temperature coefficients of 1.069 and 1.099, respectively
    Characterization and anaerobic biodegradability of grey water
    Hernandez Leal, L. ; Temmink, B.G. ; Zeeman, G. ; Buisman, C.J.N. - \ 2011
    Desalination 270 (2011)1-3. - ISSN 0011-9164 - p. 111 - 115.
    greywater treatment - treatment systems - surfactants - toxicity - boron - experiences - irrigation - quality - reactor - sludge
    Grey water consists of the discharges from kitchen sinks, showers, baths, washing machines and hand basins. Thorough characterization of 192 time proportional samples of grey water from 32 houses was conducted over a period of 14 months. COD concentrations were 724 ± 150 mg L- 1, of which 34% was present as suspended COD, 25% as colloidal COD and 38% as soluble COD. The maximum anaerobic biodegradability of grey water of 70 ± 5% indicates the possibility of recovering the COD as methane. However, the low hydrolysis constant makes the application of anaerobic treatment unsuitable. Surfactants accounted for 15% of the total COD. The concentrations of anionic, cationic and noninonic surfactants were 41.1 ± 12.1 mg L- 1, 1.7 ± 0.8 mg L- 1 and 11.3 ± 3.9 mg L- 1, respectively. Of the trace elements which were measured were present below limits suggested for irrigation. Only boron (0.53 ± 0.19 mg L- 1) in a few measurements exceeded the 0.75 mg L- 1 limit established for long term irrigation.
    Hydrogenotrophic Sulfate Reduction in a Gas-Lift Bioreactor Operated at 9 degrees C
    Nevatalo, L.M. ; Bijmans, M.F.M. ; Lens, P.N.L. ; Kaksonen, A.H. ; Puhakka, J.A. - \ 2010
    Journal of Microbiology and Biotechnology 20 (2010)3. - ISSN 1017-7825 - p. 615 - 621.
    reducing bacteria - retention time - carbon-dioxide - growth-rate - sp-nov - reactor - temperature - methanogenesis - oxidation - sulfide
    The viability of low-temperature sulfate reduction with hydrogen as electron donor was studied with a bench-scale gas-lift bioreactor (GLB) operated at 9 degrees C. Prior to the GLB experiment, the temperature range of sulfate reduction of the inoculum was assayed. The results of the temperature gradient assay indicated that the inoculum was a psychrotolerant mesophilic enrichment culture that had an optimal temperature for sulfate reduction of 31 degrees C, and minimum and maximum temperatures of 7 degrees C and 41 degrees C, respectively. In the GLB experiment at 9 degrees C, a sulfate reduction rate of 500-600 mg l(-1) d(-1), corresponding to a specific activity of 173 mg SO42- g VSS-1 d(-1), was obtained. The electron flow from the consumed H-2-gas to sulfate reduction varied between 27% and 52%, whereas the electron flow to acetate production decreased steadily from 15% to 5%. No methane was produced. Acetate was produced from CO2 and H-2 by homoacetogenic bacteria. Acetate supported the growth of some heterotrophic sulfate-reducing bacteria. The sulfate reduction rate in the GLB was limited by the slow biomass growth rate at 9 degrees C and low biomass retention in the reactor. Nevertheless, this study demonstrated the potential sulfate reduction rate of psychrotolerant sulfate-reducing mesophiles at suboptimal temperature.
    An intracellular pH gradient in the anammox bacterium Kuenenia stuttgartiensis as evaluated by P-31 NMR
    Star, W.R.L. van der; Dijkema, C. ; Waard, P. de; Picioreanu, C. ; Strous, M. ; Loosdrecht, M.C.M. van - \ 2010
    Applied Microbiology and Biotechnology 86 (2010)1. - ISSN 0175-7598 - p. 311 - 317.
    ammonium-oxidizing bacteria - nuclear-magnetic-resonance - proton gradients - 4 genera - compartmentation - enrichment - oxidation - reactor - cells - identification
    The cytoplasm of anaerobic ammonium oxidizing (anammox) bacteria consists of three compartments separated by membranes. It has been suggested that a proton motive force may be generated over the membrane of the innermost compartment, the "anammoxosome". P-31 nuclear magnetic resonance (NMR) spectroscopy was employed to investigate intracellular pH differences in the anammox bacterium Kuenenia stuttgartiensis. With in vivo NMR, spectra were recorded of active, highly concentrated suspensions of K. stuttgartiensis in a wide-bore NMR tube. At different external pH values, two stable and distinct phosphate peaks were apparent in the recorded spectra. These peaks were equivalent with pH values of 7.3 and 6.3 and suggested the presence of a proton motive force over an intracytoplasmic membrane in K. stuttgartiensis. This study provides for the second time-after discovery of acidocalcisome-like compartments in Agrobacterium tumefaciens-evidence for an intracytoplasmic pH gradient in a chemotrophic prokaryotic cell
    Characterization of the Mineral Fraction Associated to Extracellular Polymeric Substances (EPS) in Anaerobic Granular Sludges
    Abzac, P. D'; Bordas, F. ; Joussein, E. ; Hullebusch, E. ; Lens, P.N.L. ; Guibaud, G. - \ 2010
    Environmental Science and Technology 44 (2010)1. - ISSN 0013-936X - p. 412 - 418.
    waste-water - extraction methods - heavy-metals - part i - removal - sulfate - reactor - mechanisms - dynamics - sorption
    The extracellular polymeric substances (EPS) extracted from four anaerobic granular sludges contain an important mineral fraction (20-77% of the EPS dry weight). The composition of the mineral fraction of EPS depends strongly of the extraction method applied and to a lesser extend of the origin of the anaerobic sludge. Centrifugation, sonication, and heating extraction procedures yield a similar mineral composition. However, extraction using a cationic exchange resin (CER) leads to an increase of the Na+ content in the EPS extract because the CER promotes an exchange of divalent and trivalent inorganic elements in the EPS extracts toward Na+. Chemical extraction protocols were also shown to contaminate the EPS extracts by impurities or carry over of the extractant itself (e.g., ethanol). A part of the mineral fraction is bound to the EPS organic matter and structures the EPS matrix in the granules. Scanning electron microscopic analysis (SEM-EDX) showed that in addition, solid particles such as CaCO3 and Ca5OH(PO4)(3) containing various metallic elements (i.e., Al, Fe, Cu, Mn...) are present in the EPS as well. This inorganic fraction, too often neglected in EPS studies, can influence the physicochemical properties of EPS.
    Bioflocculation of grey water for improved energy recovery within decentralized sanitation concepts
    Hernandez Leal, L. ; Temmink, B.G. ; Zeeman, G. ; Buisman, C.J.N. - \ 2010
    Bioresource Technology 101 (2010)23. - ISSN 0960-8524 - p. 9065 - 9070.
    reactor - fate
    Bioflocculation of grey water was tested with a lab-scale membrane bioreactor in order to concentrate the COD. Three concentration factors were tested based on the ratio of sludge retention time (SRT) and hydraulic retention time (HRT): 3, 8 and 12. COD concentration factor was up to 7.1, achieving a final concentration of 7.2 g COD L(-1). Large fractions of suspended COD were recovered in the concentrate (57%, 81% and 82% at SRT/HRT ratios of 3, 8 and 12, respectively) indicating a strong bioflocculation of grey water. A maximum of 11% of COD mineralization of grey water was measured at the longest SRT tested (1 d). The integration of bioflocculation of grey water in decentralized sanitation concepts may increase the overall production of methane by 73%, based on the biogas produced by black water only. Therefore, bioflocculation is a promising grey water pre-treatment step for energy recovery within decentralized sanitation concepts
    Dosing of anaerobic granular sludge bioreactors with cobalt: Impact of cobalt retention on methanogenic activity
    Fermoso, F.G. ; Bartacek, J. ; Manzano, R. ; Leeuwen, H.P. van; Lens, P.N.L. - \ 2010
    Bioresource Technology 101 (2010)24. - ISSN 0960-8524 - p. 9429 - 9437.
    degradation - vitamin-b-12 - reactor - nickel - iron - deprivation - cadmium - ions
    The effect of dosing a metal limited anaerobic sludge blanket (UASB) reactor with a metal pulse on the methanogenic activity of granular sludge has thus far not been successfully modeled. The prediction of this effect is crucial in order to optimize the strategy for metal dosage and to prevent unnecessary losses of resources. This paper describes the relation between the initial immobilization of cobalt in anaerobic granular sludge cobalt dosage into the reactor and the evolution of methanogenic activity during the subsequent weeks. An operationally defined parameter (A0·B0) was found to combine the amount of cobalt immobilized instantaneously upon the pulse (B0) and the amount of cobalt immobilized within the subsequent 24 h (A0). In contrast with the individual parameters A0 and B0, the parameter A0·B0 correlated significantly with the methanogenic activity of the sludge during the subsequent 16 or 35 days. This correlation between metal retention and activity evolution is a useful tool to implement trace metal dosing strategies for biofilm-based biotechnological processes.
    Identification and predictive control of a multistage evaporator
    Atuonwu, J.C. ; Cao, Y. ; Rangaiah, G.P. ; Tadé, M.O. - \ 2010
    Control Engineering Practice 18 (2010)12. - ISSN 0967-0661 - p. 1418 - 1428.
    recurrent neural-networks - automatic differentiation - multivariable processes - system-identification - models - reactor - backpropagation - temperature - inverse - time
    A recurrent neural network-based nonlinear model predictive control (NMPC) scheme in parallel with PI control loops is developed for a simulation model of an industrial-scale five-stage evaporator. Input–output data from system identification experiments are used in training the network using the Levenberg–Marquardt algorithm with automatic differentiation. The same optimization algorithm is used in predictive control of the plant. The scheme is tested with set-point tracking and disturbance rejection problems on the plant while control performance is compared with that of PI controllers, a simplified mechanistic model-based NMPC developed in previous work and a linear model predictive controller (LMPC). Results show significant improvements in control performance by the new parallel NMPC–PI control scheme
    Maximum Photosynthetic Yield of Green Microalgae in Photobioreactors
    Zijffers, J.F. ; Schippers, K.J. ; Ke Zheng, ; Janssen, M.G.J. ; Tramper, J. ; Wijffels, R.H. - \ 2010
    Marine Biotechnology 12 (2010)6. - ISSN 1436-2228 - p. 708 - 718.
    panel photobioreactor - light energy - a-stat - flat - optimization - cultures - density - biomass - reactor - growth
    The biomass yield on light energy of Dunaliella tertiolecta and Chlorella sorokiniana was investigated in a 1.25- and 2.15-cm light path panel photobioreactor at constant ingoing photon flux density (930 µmol photons m-2¿s-1). At the optimal combination of biomass density and dilution rate, equal biomass yields on light energy were observed for both light paths for both microalgae. The observed biomass yield on light energy appeared to be based on a constant intrinsic biomass yield and a constant maintenance energy requirement per gram biomass. Using the model of Pirt (New Phytol 102:3–37, 1986), a biomass yield on light energy of 0.78 and 0.75 g¿mol photons-1 and a maintenance requirement of 0.0133 and 0.0068 mol photons g-1¿h-1 were found for D. tertiolecta and C. sorokiniana, respectively. The observed yield decreases steeply at low light supply rates, and according to this model, this is related to the increase of the amount of useable light energy diverted to biomass maintenance. With this study, we demonstrated that the observed biomass yield on light in short light path bioreactors at high biomass densities decreases because maintenance requirements are relatively high at these conditions. All our experimental data for the two strains tested could be described by the physiological models of Pirt (New Phytol 102:3–37, 1986). Consequently, for the design of a photobioreactor, we should maintain a relatively high specific light supply rate. A process with high biomass densities and high yields at high light intensities can only be obtained in short light path photobioreactors
    Biohydrogen production from beet molasses by sequential dark and photofermentation
    Özgür, E. ; Mars, A.E. ; Peksel, B. ; Louwerse, A. ; Yücel, M. ; Gündüz, U. ; Claassen, P.A.M. ; Eroglu, I. - \ 2010
    International Journal of Hydrogen Energy 35 (2010)2. - ISSN 0360-3199 - p. 511 - 517.
    rhodobacter-sphaeroides ou001 - ethanol-type fermentation - hydrogen-production - caldicellulosiruptor-saccharolyticus - anaerobic fermentation - photo-fermentation - capsulatus - bioreactor - pathway - reactor
    Biological hydrogen production using renewable resources is a promising possibility to generate hydrogen in a sustainable way. In this study, a sequential dark and photofermentation has been employed for biohydrogen production using sugar beet molasses as a feedstock. An extreme thermophile Caldicellulosiruptor saccharolyticus was used for the dark fermentation, and several photosynthetic bacteria (Rhodobacter capsulatus wild type, R. capsulatus hup- mutant, and Rhodopseudomonas palustris) were used for the photofermentation. C. saccharolyticus was grown in a pH-controlled bioreactor, in batch mode, on molasses with an initial sucrose concentration of 15 g/L. The influence of additions of NH4+ and yeast extract on sucrose consumption and hydrogen production was determined. The highest hydrogen yield (4.2 mol of H2/mol sucrose) and maximum volumetric productivity (7.1 mmol H2/Lc.h) were obtained in the absence of NH4+. The effluent of the dark fermentation containing no NH4+ was fed to a photobioreactor, and hydrogen production was monitored under continuous illumination, in batch mode. Productivity and yield were improved by dilution of the dark fermentor effluent (DFE) and the additions of buffer, iron-citrate and sodium molybdate. The highest hydrogen yield (58% of the theoretical hydrogen yield of the consumed organic acids) and productivity (1.37 mmol H2/Lc.h) were attained using the hup- mutant of R. capsulatus. The overall hydrogen yield from sucrose increased from the maximum of 4.2 mol H2/mol sucrose in dark fermentation to 13.7 mol H2/mol sucrose (corresponding to 57% of the theoretical yield of 24 mol of H2/mole of sucrose) by sequential dark and photofermentation.
    Aquatic worms eat sludge: mass balances and processing of worm faeces
    Hendrickx, T.L.G. ; Temmink, B.G. ; Elissen, H.J.H. ; Buisman, C.J.N. - \ 2010
    Journal of Hazardous Materials 177 (2010)1-3. - ISSN 0304-3894 - p. 633 - 638.
    waste-water-treatment - activated-sludge - reduction - removal - reactor
    Reduction of the amount of waste sludge from waste water treatment plants (WWTPs) can be achieved with the aquatic worm Lumbriculus variegatus in a new reactor concept. In addition to reducing the amount of waste sludge, further processing of produced worm faeces and released nutrients should also be considered. This study gives the mass balances for sludge consumed by L. variegatus, showing the fate of the consumed organic material, nutrients and heavy metals associated with the sludge. A distinction is made between conversion into worm biomass, release as dissolved metabolites and what remains in the worm faeces. The results showed that 39% of the nitrogen and 12% of the phosphorus in the sludge digested by the worms are used in the formation of new worm biomass, which has potential for reuse. Experiments showed that settling of the worm faeces leads to a factor 2.5 higher solids concentration, compared to settling of waste sludge. This could lead to a 67% reduction of the volumetric load on thickening equipment. The worm reactor is expected to be most interesting for smaller WWTPs where a decrease on the volumetric load on sludge handling operations will have most impact
    Grey water treatment in a series anaerobic – Aerobic system for irrigation
    Abu-Ghunmi, L.N.A.H. ; Zeeman, G. ; Fayyad, M. ; Lier, J.B. van - \ 2010
    Bioresource Technology 101 (2010)1. - ISSN 0960-8524 - p. 41 - 50.
    greywater treatment - reuse - reactor - technologies - quality
    This study aims at treatment of grey water for irrigation, focusing on a treatment technology that is robust, simple to operate and with minimum energy consumption. The result is an optimized system consisting of an anaerobic unit operated in upflow mode, with a 1 day operational cycle, a constant effluent flow rate and varying liquid volume. Subsequent aerobic step is equipped with mechanical aeration and the system is insulated for sustaining winter conditions. The COD removal achieved by the anaerobic and aerobic units in summer and winter are 45%, 39% and 53%, 64%, respectively. Sludge in the anaerobic and aerobic reactor has a concentration of 168 and 8 mg VS L-1, respectively. Stability of sludge in the anaerobic and aerobic reactors is 80% and 93%, respectively, based on COD. Aerobic effluent quality, except for pathogens, agrees with the proposed irrigation water quality guidelines for reclaimed water in Jordan.
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