UASB Reactor (uasb + reactor)

Distribution by Scientific Domains


Selected Abstracts


Thermophilic (55,65 C) and Extreme Thermophilic (70,80 C) Sulfate Reduction in Methanol and Formate-Fed UASB Reactors

BIOTECHNOLOGY PROGRESS, Issue 5 2004
Marcus V. G. Vallero
The feasibility of thermophilic (55,65 C) and extreme thermophilic (70,80 C) sulfate-reducing processes was investigated in three lab-scale upflow anaerobic sludge bed (UASB) reactors fed with either methanol or formate as the sole substrates and inoculated with mesophilic granular sludge previously not exposed to high temperatures. Full methanol and formate degradation at temperatures up to, respectively, 70 and 75 C, were achieved when operating UASB reactors fed with sulfate rich (COD/SO42 - = 0.5) synthetic wastewater. Methane-producing archaea (MPA) outcompeted sulfate-reducing bacteria (SRB) in the formate-fed UASB reactor at all temperatures tested (65,75 C). In contrast, SRB outcompeted MPA in methanol-fed UASB reactors at temperatures equal to or exceeding 65 C, whereas strong competition between SRB and MPA was observed in these reactors at 55 C. A short-term (5 days) temperature increase from 55 to 65 C was an effective strategy to suppress methanogenesis in methanol-fed sulfidogenic UASB reactors operated at 55 C. Methanol was found to be a suitable electron donor for sulfate-reducing processes at a maximal temperature of 70 C, with sulfide as the sole mineralization product of methanol degradation at that temperature. [source]


Post-treatment of anaerobically treated medium-age landfill leachate

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 1 2010
Ebru Akkaya
Abstract This study focused on the removal of COD and NH4+ from medium-age leachate. Experiments were performed in a laboratory-scale upflow anaerobic sludge blanket (UASB), a membrane bioreactor (MBR), and using magnesium ammonium phosphate (MAP) precipitation. MBR and MAP were used for the post-treatment steps for anaerobically treated leachate to increase the removal of organics and ammonium. The UASB reactor removed nearly all biodegradable organics and supplied constant effluent COD for all concentration ranges of influent leachate. Ammonium removal efficiency in the UASB reactor was relatively low and the average value was ,7.9%. Integration of MBR to the effluent of UASB reactor increased the average COD removal efficiency from 51.8 to 65.6% and maximum removal efficiency increased to 74.3%. MAP precipitation was applied as a final step to decrease the ammonium concentration in the effluent of UASB+MBR reactors. The effect of pH and the molar ratio of MAP constituents on the removal of ammonium were evaluated. At optimal conditions (pH: 9.0 and Mg/NH4/PO4: 1/1.2/1.2), 96.6% of ammonium was removed and MAP provided additional COD and turbidity treatment. Consequently, the combined system of MBR and MAP precipitation could be used as an appropriate post treatment option for the anaerobically treated medium-age landfill leachate. 2009 American Institute of Chemical Engineers Environ Prog, 2010 [source]


Effect of loading rate on TOC consumption efficiency in a sulfate reducing process: sulfide effect in batch culture

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 12 2008
Citlali Garca-Saucedo
Abstract BACKGROUND: The sulfate reducing process (SRP) was analyzed in order to identify factors that diminish the effectiveness of the SRP during wastewater treatment. The effect of different sulfate loading rates (SLR, 290 to 981 mg SO4 -S L,1d,1) and lactate at a stoichiometric C/S ratio of 0.75 on SRP was studied in an upflow anaerobic sludge blanket (UASB) reactor. The effect of sulfide concentration (0 to 200 mg sulfide-S L,1) on SRP in batch culture was evaluated. RESULTS: When the SLR was increased, the total organic carbon (TOC) and sulfate consumption efficiencies decreased from 93% 3 to 66% 2 and 60% 5 to 45% 4, respectively. Acetate and propionate were accumulated. Microbial analysis showed the presence of microorganisms related with the SRP, fermentation and methanogenesis. In batch culture, when lactate and sulfate were present, SRP and fermentation were observed. When sulfide was added only SRP was observed. At concentrations higher than 150 mg sulfide-S L,1 the efficiencies, yields and specific consumption rates (q) decreased. CONCLUSION: Based on the sulfide-S/volatile suspended solid ratio, it was found that the decrease in efficiency and accumulation of acetate and propionate in the UASB reactor was not related to sulfide inhibition but to the q of acetate and propionate, which were up to 11 times lower than lactate. Copyright 2008 Society of Chemical Industry [source]


Hydrodynamics of upflow anaerobic sludge blanket reactors

AICHE JOURNAL, Issue 2 2009
Ting-Ting Ren
Abstract The hydrodynamic characteristics of upflow anaerobic sludge blanket (UASB) reactors were investigated in this study. A UASB reactor was visualized as being set-up of a number of continuously stirred tank reactors (CSTRs) in series. An increasing-sized CSTRs (ISC) model was developed to describe the hydrodynamics of such a bioreactor. The gradually increasing tank size in the ISC model implies that the dispersion coefficient decreased along the axial of the UASB reactor and that its hydrodynamic behavior was basically dispersion-controlled. Experimental results from both laboratory-scale H2 -producing and full-scale CH4 -producing UASB reactors were used to validate this model. Simulation results demonstrate that the ISC model was better than the other models in describing the hydrodynamics of the UASB reactors. Moreover, a three-dimensional computational fluid dynamics (CFD) simulation was performed with an Eulerian-Eulerian three-phase-fluid approach to visualize the phase holdup and to explore the flow patterns in UASB reactors. The results from the CFD simulation were comparable with those of the ISC model predictions in terms of the flow patterns and dead zone fractions. The simulation results about the flow field further confirm the discontinuity in the mixing behaviors throughout a UASB reactor. 2008 American Institute of Chemical Engineers AIChE J, 2009 [source]


Improvement in biomass characteristics and degradation efficiency in modified UASB reactor treating municipal sewage: a comparative study with UASB reactor

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009
Suprotim Das
Abstract Low strength wastewaters (LSWs) are difficult to degrade efficiently in the upflow anaerobic sludge blanket (UASB) reactor. The possible reasons for poor treatment of LSWs in UASB are: (i) low mixing due to low biogas production (ii) frequent biomass washout at higher hydraulic loading rate due to low settleability of biomass. In the present study, lab scale UASB reactor and modified upflow anaerobic sludge blanket (MUASB) reactor were operated with municipal sewage containing chemical oxygen demand (COD) in range of 180,210 mg L,1 as LSW at three different hydraulic retention times (HRTs) of 8, 6, and 4 h. The changes in the biomass characteristics as well as degradation efficiency were compared with respect to time. During this operation, samples of biomass were taken from both reactors to measure total suspended solids (TSS), settling velocity, granular size and specific methanogenic activity (SMA). The overall COD removal in MUASB reactor was higher compared to UASB (84 and 67% respectively). After 150 days of operation, the settling velocity and SMA of MUASB biomass increased, but no significant change in settling velocity and SMA of UASB biomass was observed. The study shows that MUASB could be preferred over UASB for the treatment of municipal sewage as LSW. Copyright 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]


Anaerobic digestion as final step of a cellulosic ethanol biorefinery: Biogas production from fermentation effluent in a UASB reactor,pilot-scale results

BIOTECHNOLOGY & BIOENGINEERING, Issue 1 2010
H. Uellendahl
Abstract In order to lower the costs for second generation bioethanol from lignocellulosic biomass anaerobic digestion of the effluent from ethanol fermentation was implemented using an upflow anaerobic sludge blanket (UASB) reactor system in a pilot-scale biorefinery plant. Both thermophilic (53C) and mesophilic (38C) operation of the UASB reactor was investigated. At an OLR of 3.5,kg-VS/(m3,day) a methane yield of 340,L/kg-VS was achieved for thermophilic operation (53C) while 270,L/kg-VS was obtained under mesophilic conditions (38C). For loading rates higher than 5,kg-VS/(m3,day) the methane yields were, however, higher under mesophilic conditions compared to thermophilic conditions. The conversion of dissolved organic matter (VSdiss) was between 68% and 91%. The effluent from the ethanol fermentation showed no signs of toxicity to the anaerobic microorganisms. However, a high content of suspended matter reduced the degradation efficiency. The retention time of the anaerobic system could be reduced from 70 to 7,h by additional removal of suspended matter by clarification. Implementation of the biogas production from the fermentation effluent accounted for about 30% higher carbon utilization in the biorefinery compared to a system with only bioethanol production. Biotechnol. Bioeng. 2010;107: 59,64. 2010 Wiley Periodicals, Inc. [source]


Purification of bioethanol effluent in an UASB reactor system with simultaneous biogas formation

BIOTECHNOLOGY & BIOENGINEERING, Issue 1 2003
M. Torry-Smith
In this study, the prospect of using an Upflow Anaerobic Sludge Blanket (UASB) reactor for detoxification of process water derived from bioethanol production has been investigated. The bioethanol effluent (BEE) originated from wet oxidized wheat straw fermented by Saccharomyces cerevisiae and Thermoanaerobacter mathranii A3M4 to produce ethanol from glucose and xylose, respectively. In batch experiments the methane potential of BEE was determined to 529 mL-CH4/g-VS. In batch degradation experiments it was shown that the presence of BEE had a positive influence on the removal of the inhibitors 2-furoic acid, 4-hydroxyacetophenone, and acetovanillone as compared to conversion of the inhibitors as sole substrate in synthetic media. Furthermore, experiments were carried out treating BEE in a laboratory-scale UASB reactor. The results showed a Chemical Oxygen Demand (COD) removal of 80% (w/w) at an organic loading rate of 29 g-COD/(L d). GC analysis of the lignocellulosic related potentially inhibitory compounds 2-furoic acid, vanillic acid, homovanillic acid, acetovanillone, syringic acid, acetosyringone, syringol, 4-hydroxybenzoic acid, and 4-hydroxybenzaldehyde showed that all of these compounds were removed from the BEE in the reactor. Implementation of a UASB purification step was found to be a promising approach to detoxify process water from bioethanol production allowing for recirculation of the process water and reduced production costs. 2003 Wiley Periodicals, Inc. Biotechnol Bioeng 84: 7,12, 2003. [source]


Thermophilic (55,65 C) and Extreme Thermophilic (70,80 C) Sulfate Reduction in Methanol and Formate-Fed UASB Reactors

BIOTECHNOLOGY PROGRESS, Issue 5 2004
Marcus V. G. Vallero
The feasibility of thermophilic (55,65 C) and extreme thermophilic (70,80 C) sulfate-reducing processes was investigated in three lab-scale upflow anaerobic sludge bed (UASB) reactors fed with either methanol or formate as the sole substrates and inoculated with mesophilic granular sludge previously not exposed to high temperatures. Full methanol and formate degradation at temperatures up to, respectively, 70 and 75 C, were achieved when operating UASB reactors fed with sulfate rich (COD/SO42 - = 0.5) synthetic wastewater. Methane-producing archaea (MPA) outcompeted sulfate-reducing bacteria (SRB) in the formate-fed UASB reactor at all temperatures tested (65,75 C). In contrast, SRB outcompeted MPA in methanol-fed UASB reactors at temperatures equal to or exceeding 65 C, whereas strong competition between SRB and MPA was observed in these reactors at 55 C. A short-term (5 days) temperature increase from 55 to 65 C was an effective strategy to suppress methanogenesis in methanol-fed sulfidogenic UASB reactors operated at 55 C. Methanol was found to be a suitable electron donor for sulfate-reducing processes at a maximal temperature of 70 C, with sulfide as the sole mineralization product of methanol degradation at that temperature. [source]


Multiparameter models for performance analysis of UASB reactors

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2008
C M Narayanan
Abstract BACKGROUND: UASB (upflow anaerobic sludge blanket) bioreactors have the distinct advantage that they do not demand support particles and provide a high rate of bioconversion even with high strength feedstocks. Although apparently simple in construction, the performance analysis of these reactors involves a high degree of mathematical complexity. Most simulation models reported in the literature are rudimentary in nature as they involve gross approximations. In the present paper, two multiparameter simulation packages are presented that make no simplifying assumptions and hence are more rigorous in nature. RESULTS: The first package assumes the sludge bed to be a plug-flow reactor (PFR) and the sludge blanket to be an ideal continuous stirred tank reactor (CSTR). The second package equates the reactor to a plug flow dispersion reactor (PFDR), the axial dispersion coefficient however being a function of axial distance. The three phase nature of the sludge blanket has been considered and the variation of gas velocity in the axial direction has been taken into account. Three different kinetic equations have been considered. Resistance to diffusion of substrate into sludge granules has been accounted for by incorporating appropriately defined effectiveness factors. The applicability of simulation packages developed has been ascertained by comparing with real-life data collected from industrial/pilot plant/laboratory UASB reactors. The maximum deviation observed is 15%. CONCLUSIONS: Although the software packages developed have high computational load, their applicability has been successfully ascertained and they may be recommended for design and installation of industrial UASB reactors and also for the rating of existing installations. Copyright 2008 Society of Chemical Industry [source]


Temperature dependency of granule characteristics and kinetic behavior in UASB reactors

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2004
Hsin-Hsien Chou
Abstract When an inhibitory substrate, phenol, was treated under mesophilic conditions (25, 30, 35, and 40 C), the upflow anaerobic sludge bed (UASB) reactors at 30 C resulted in the greatest amount of biomass and the largest granule size, while the UASB reactors at 25 C resulted in the smallest granule size and the greatest amount of wash-out of sludge. The granule size tended to be negatively correlated with the amount of wash-out of sludge. With an increase in temperature, the kinetic constant k for anaerobic phenol degradation increased and the half saturation constant (Ks) decreased. The mass fraction of methanogens (f) increased with increasing operational temperature in the UASB reactors and the activation energy (Ea) for acetate methanogenesis was larger than that for phenol acidogenesis in the batch reactors, indicating that the operational temperature imposes a more influential effect on methanogens than on acidogens. From the results of the activity of acidogens and methanogens (expressed in specific COD utilization rate), the rate-limiting step is phenol acidogenesis. Copyright 2004 Society of Chemical Industry [source]


Effects of cationic polymer on start-up and granulation in upflow anaerobic sludge blanket reactors

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2004
Ying Wang
Abstract The upflow anaerobic sludge blanket (UASB) has been used successfully to treat a variety of industrial wastewaters. It offers a high degree of organics removal, low sludge production and low energy consumption, along with energy production in the form of biogas. However, two major drawbacks are its long start-up period and deficiency of active biogranules for proper functioning of the process. In this study, the influence of a coagulant polymer on start-up, sludge granulation and the associated reactor performance was evaluated in four laboratory-scale UASB reactors. A control reactor (R1) was operated without added polymer, while the other three reactors, designated R2, R3 and R4, were operated with polymer concentrations of 5 mg dm,3, 10 mg dm,3 and 20 mg dm,3, respectively. Adding the polymer at a concentration of 20 mg dm,3 markedly reduced the start-up time. The time required to reach stable treatment at an organic loading rate (OLR) of 4.8 g COD dm,3 d,1 was reduced by more than 36% (R4) as compared with both R1 and R3, and by 46% as compared with R2. R4 was able to handle an OLR of 16 g COD dm,3 d,1 after 93 days of operation, while R1, R2 and R3 achieved the same loading rate only after 116, 116 and 109 days respectively. Compared with the control reactor, the start-up time of R4 was shortened by about 20% at this OLR. Granule characterization indicated that the granules developed in R4 with 20 mg dm,3 polymer exhibited the best settleability and methanogenic activity at all OLRs. The organic loading capacities of the reactors were also increased by the addition of polymer. The maximum organic loading of the control reactor (R1) without added polymer was 19.2 g COD dm,3 d,1, while the three polymer-assisted reactors attained a marked increase in organic loading of 25.6 g COD dm,3 d,1. Adding the cationic polymer could result in shortening of start-up time and enhancement of granulation, which may in turn lead to improvement in the efficiency of organics removal and loading capacity of the UASB system. Copyright 2004 Society of Chemical Industry [source]


Hydrodynamics of upflow anaerobic sludge blanket reactors

AICHE JOURNAL, Issue 2 2009
Ting-Ting Ren
Abstract The hydrodynamic characteristics of upflow anaerobic sludge blanket (UASB) reactors were investigated in this study. A UASB reactor was visualized as being set-up of a number of continuously stirred tank reactors (CSTRs) in series. An increasing-sized CSTRs (ISC) model was developed to describe the hydrodynamics of such a bioreactor. The gradually increasing tank size in the ISC model implies that the dispersion coefficient decreased along the axial of the UASB reactor and that its hydrodynamic behavior was basically dispersion-controlled. Experimental results from both laboratory-scale H2 -producing and full-scale CH4 -producing UASB reactors were used to validate this model. Simulation results demonstrate that the ISC model was better than the other models in describing the hydrodynamics of the UASB reactors. Moreover, a three-dimensional computational fluid dynamics (CFD) simulation was performed with an Eulerian-Eulerian three-phase-fluid approach to visualize the phase holdup and to explore the flow patterns in UASB reactors. The results from the CFD simulation were comparable with those of the ISC model predictions in terms of the flow patterns and dead zone fractions. The simulation results about the flow field further confirm the discontinuity in the mixing behaviors throughout a UASB reactor. 2008 American Institute of Chemical Engineers AIChE J, 2009 [source]


Explaining the enhanced performance of pulsed bioreactors by mechanistic modeling

AICHE JOURNAL, Issue 5 2008
Amaya Franco
Abstract In this work, steady-state mass balance based models were applied to two UASB reactors and three UAF for a better understanding of the role of pulsation on the efficacy improvement. Models were defined taking into account the hydraulic behavior of each digester and the limiting mechanism of the overall process kinetics (mass transfer or biochemical reaction rate). The application of the model allows to identify that mass transfer was the controlling step in all the reactors, except for the nonpulsed UASB, where methanogenic activity controlled the reactor performance in the last operation steady states. Mass transfer coefficients were higher for pulsed reactors and, in general, a good agreement between those estimated by an empirical correlation and from the model was obtained. Damkhler number values supported that the external mass transfer resistance was not negligible with respect to the process kinetic and in addition, in most cases, it controls the overall process in the reactors. The relative importance of external and internal mass transfer rate was calculated through the Biot number. The values of this dimensionless module indicated that external transport was the main contributor to overall mass transfer resistance. 2008 American Institute of Chemical Engineers AIChE J, 2008 [source]


Effects of process stability on anaerobic biodegradation of LAS in UASB reactors

BIOTECHNOLOGY & BIOENGINEERING, Issue 7 2005
Trine Lbner
Abstract Anaerobic biodegradation of linear alkylbenzene sulfonates (LAS) was studied in upflow anaerobic sludge blanket (UASB) reactors operated under mesophilic (37C) and thermophilic (55C) conditions. LAS C12 concentration in the influents was 10 mgL,1, and the hydraulic retention time in the reactors was 2 days. Adsorption of LAS C12 was assessed in an autoclaved control reactor and ceased after 115 days. The reactors were operated for a minimum of 267 days; 40,80% removal of LAS C12 was observed. A temperature reduction from 55C to 32C for 30 h resulted in process imbalance as indicated by increase of volatile fatty acids (VFA). The imbalance was much more intense in the LAS amended reactor compared with an unamended reactor. At the same time, the process imbalance resulted in discontinued LAS removal. This finding indicates that process stability is a key factor in anaerobic biological removal of LAS. After a recovery period, the removal of LAS resumed, providing evidence of biological anaerobic LAS degradation. The removal remained constant until termination of experiments in the reactor. Biodegradation of LAS in the mesophilic reactor was at the same level as in the thermophilic reactor under stable conditions. 2005 Wiley Periodicals, Inc. [source]


Thermophilic (55,65 C) and Extreme Thermophilic (70,80 C) Sulfate Reduction in Methanol and Formate-Fed UASB Reactors

BIOTECHNOLOGY PROGRESS, Issue 5 2004
Marcus V. G. Vallero
The feasibility of thermophilic (55,65 C) and extreme thermophilic (70,80 C) sulfate-reducing processes was investigated in three lab-scale upflow anaerobic sludge bed (UASB) reactors fed with either methanol or formate as the sole substrates and inoculated with mesophilic granular sludge previously not exposed to high temperatures. Full methanol and formate degradation at temperatures up to, respectively, 70 and 75 C, were achieved when operating UASB reactors fed with sulfate rich (COD/SO42 - = 0.5) synthetic wastewater. Methane-producing archaea (MPA) outcompeted sulfate-reducing bacteria (SRB) in the formate-fed UASB reactor at all temperatures tested (65,75 C). In contrast, SRB outcompeted MPA in methanol-fed UASB reactors at temperatures equal to or exceeding 65 C, whereas strong competition between SRB and MPA was observed in these reactors at 55 C. A short-term (5 days) temperature increase from 55 to 65 C was an effective strategy to suppress methanogenesis in methanol-fed sulfidogenic UASB reactors operated at 55 C. Methanol was found to be a suitable electron donor for sulfate-reducing processes at a maximal temperature of 70 C, with sulfide as the sole mineralization product of methanol degradation at that temperature. [source]