On the basis of continuous tests and batch tests, conversion regular patterns of acetate, propionate and butyrate in activated sludge at different heights of the UASB reactor were conducted. Results indicated that the...On the basis of continuous tests and batch tests, conversion regular patterns of acetate, propionate and butyrate in activated sludge at different heights of the UASB reactor were conducted. Results indicated that the conversion capacity of the microbe is decided by the substrate characteristic when sole VFA is used as the only substrate. But when mixed substrates are used,the conversion regulations would have changed accordingly. Relationships of different substrates vary according to their locations. In the whole reactor, propionate's conversion is restrained by acetate and butyrate of high concentration. On the top and at the bottom of the reactor, conversion of acetate, but butyrate, is restrained by propionate. And in the midst, acetate's conversion is accelerated by propionate while that of butyrate is restrained. It is proved, based on the analysis of specific conversion rate, that the space distribution of the microbe is the main factor that affects substrates' conversion. The ethanol type fermentation of the acidogenic phase is the optimal acid type fermentation for the two phase anaerobic process.展开更多
Three UASB reactors were operated to investigate the population dynamics of anaerobic sludge granulation. It is found that the increase of bacterial population relates to the bacterial status in anaerobic food chain a...Three UASB reactors were operated to investigate the population dynamics of anaerobic sludge granulation. It is found that the increase of bacterial population relates to the bacterial status in anaerobic food chain and relates to sludge organic loading rates. In order to form granular sludge, it is necessary to have sufficient amount of different groups of bacteria in the sludge. In our experiment, the population of fermentative bacteria, propionate degraders, butyrate degraders and methanogens is about 107-8, 105-7, 105-7 and 105-7 cells/ml respectively at the appearance of granular sludge. Filamentous methanogenic bacteria are found to be the important species in sludge granulation. Based on the results obtained, a descriptive model is proposed to describe the microbial characteristics of granulation.展开更多
The UASB reactor was used to reconstruct leachate treatment project of Beijing Asuwei Waste Sanitary Landfill Site,and the commissioning with the UASB reactor was executed.Water quality indicators were determined in t...The UASB reactor was used to reconstruct leachate treatment project of Beijing Asuwei Waste Sanitary Landfill Site,and the commissioning with the UASB reactor was executed.Water quality indicators were determined in the debugging process,and the results showed that the VFA content in the anaerobic tank was controlled within 600 mg/L,which indicated that the water quality did not have the acidified phenomenon.The COD removal efficiency was 50%approximately and NH_3-N concentration showed as light decline when operation stability in anaerobic system.展开更多
This paper concerns with the treatment of bagasse wash water, which is generated after washing the stored bagasse before its use in the paper manufacture. The bagasse wash water, treated earlier in open lagoons, is no...This paper concerns with the treatment of bagasse wash water, which is generated after washing the stored bagasse before its use in the paper manufacture. The bagasse wash water, treated earlier in open lagoons, is now treated by the anaerobic process using UASB reactor. This study, based upon an operating unit, shows that the UASB reactor reduces COD of wash water by 85% - 90%, and results in significant emission reductions. Economic analysis carried out by using financial indicators such as DSCR, Payback period and IRR reveals very attractive rate of returns and thus, greatly reduces the risks in financing such projects by the financial institutions.展开更多
A two-stage UASB reactor was employed to remove sulfate from acrylic fiber manufacturing wastewater.Mesophilic operation（35±0.5℃） was performed with hydraulic retention time（HRT） varied between 28 and 40 hr....A two-stage UASB reactor was employed to remove sulfate from acrylic fiber manufacturing wastewater.Mesophilic operation（35±0.5℃） was performed with hydraulic retention time（HRT） varied between 28 and 40 hr.Mixed liquor suspended solids（MLSS） in the reactor was maintained about 8000 mg/L.The results indicated that sulfate removal was enhanced with increasing the ratio of COD/SO24-.At low COD/SO42-,the growth of the sulfate-reducing bacteria（SRB） was carbon-limited.The optimal sulfate removal efficiencies were 75% when the HRT was no less than 38 hr.Sulfidogenesis mainly happened in the sulfate-reducing stage,while methanogenesis in the methane-producing stage.Microbes in sulfate-reducing stage performed granulation better than that in methaneproducing stage.Higher extracellular polymeric substances（EPS） content in sulfate-reducing stage helped to adhere and connect the flocculent sludge particles together.SRB accounted for about 31% both in sulfate-reducing stage and methane-producing stage at COD/SO42-ratio of 0.5,while it dropped dramatically from 34% in sulfate-reducing stage to 10% in methane-producing stage corresponding to the COD/SO42-ratio of 4.7.SRB and MPA were predominant in sulfate-reducing stage and methane-producing stage respectively.展开更多
The granular sludge of microbial fermentation systems includes various biomass-degrading enzymes and different microflora,which have significant impacts on the degradation of biomass and the stability of the system.An...The granular sludge of microbial fermentation systems includes various biomass-degrading enzymes and different microflora,which have significant impacts on the degradation of biomass and the stability of the system.An up-flow anaerobic sludge blanket(UASB)reactor was used to grow hydrogen-producing granular sludge.The results showed that the formation of the granular sludge underwent four stages,i.e.,flocculation of the sludge,formation of the flocculent sludge,swelling of the flocculent sludge,and formation of the granular sludge.The formed granular sludge mostly had regular spherical and ellipsoidal shapes with a fractal dimension of 2.08±0.4;the settling velocities were 0.84 cm/s to 1.96 cm/s in water,the porosity was 0.67-0.95.The shear sensitivity(Kss)of the granular sludge was 0.1152.The granular sludge had a culture cycle of approximately 70 d and a hydrogen yield of 1.09 mol H2/mol glucose.展开更多
Roxarsone （3-nitro-4-hydroxyphenylarsonic acid, ROX） has been widely used for decades as an organoarsenic feed additive to control intestinal parasites and improve feed efficiency in animal production. However, most...Roxarsone （3-nitro-4-hydroxyphenylarsonic acid, ROX） has been widely used for decades as an organoarsenic feed additive to control intestinal parasites and improve feed efficiency in animal production. However, most of the ROX is excreted into the manure, causing arsenic contamination in wastewater. The arsenic compounds are toxic to microorganisms, but the influence of continuous ROX loading on upflow anaerobic sludge blanket （UASB） reactor is still unknown. In this study, the impact of ROX and its degradation products on the performance of the UASB reactor and the degradation and speciation of ROX in the reactor were investigated. The UASB reactor （hydraulic retention time： 1.75 d） was operated using synthetic wastewater supplemented with ROX for a period of 260 days. With continuous ROX addition at 25.0 mg.L-1, severe inhibition to methanogenic activity occurred after 87 days operation accompanied with an accumulation of volatile fatty acids （VFAs） and a decline in pH. The decrease of added ROX concentration to 13.2 mg.L-1 did not mediate the inhibition. As（III）, As （V）, MMA（V）, DMA（V）, HAPA and an unknown arsenic compound were detected in the reactor, and a possible biotransformation pathway of ROX was proposed. Mass balance analysis of arsenic indicated that 60%-70% of the arsenic was discharged into the effluent, and 30%-40% was precipitated in the reactor. The results from this study suggest that we need to pay attention to the stability in the UASB reactors treating organoarsenic-contaminated manure and wastewater, and the effluent and sludge from the reactor tO avoid diffusion of arsenic contamination.展开更多
文摘On the basis of continuous tests and batch tests, conversion regular patterns of acetate, propionate and butyrate in activated sludge at different heights of the UASB reactor were conducted. Results indicated that the conversion capacity of the microbe is decided by the substrate characteristic when sole VFA is used as the only substrate. But when mixed substrates are used,the conversion regulations would have changed accordingly. Relationships of different substrates vary according to their locations. In the whole reactor, propionate's conversion is restrained by acetate and butyrate of high concentration. On the top and at the bottom of the reactor, conversion of acetate, but butyrate, is restrained by propionate. And in the midst, acetate's conversion is accelerated by propionate while that of butyrate is restrained. It is proved, based on the analysis of specific conversion rate, that the space distribution of the microbe is the main factor that affects substrates' conversion. The ethanol type fermentation of the acidogenic phase is the optimal acid type fermentation for the two phase anaerobic process.
文摘Three UASB reactors were operated to investigate the population dynamics of anaerobic sludge granulation. It is found that the increase of bacterial population relates to the bacterial status in anaerobic food chain and relates to sludge organic loading rates. In order to form granular sludge, it is necessary to have sufficient amount of different groups of bacteria in the sludge. In our experiment, the population of fermentative bacteria, propionate degraders, butyrate degraders and methanogens is about 107-8, 105-7, 105-7 and 105-7 cells/ml respectively at the appearance of granular sludge. Filamentous methanogenic bacteria are found to be the important species in sludge granulation. Based on the results obtained, a descriptive model is proposed to describe the microbial characteristics of granulation.
文摘The UASB reactor was used to reconstruct leachate treatment project of Beijing Asuwei Waste Sanitary Landfill Site,and the commissioning with the UASB reactor was executed.Water quality indicators were determined in the debugging process,and the results showed that the VFA content in the anaerobic tank was controlled within 600 mg/L,which indicated that the water quality did not have the acidified phenomenon.The COD removal efficiency was 50%approximately and NH_3-N concentration showed as light decline when operation stability in anaerobic system.
文摘This paper concerns with the treatment of bagasse wash water, which is generated after washing the stored bagasse before its use in the paper manufacture. The bagasse wash water, treated earlier in open lagoons, is now treated by the anaerobic process using UASB reactor. This study, based upon an operating unit, shows that the UASB reactor reduces COD of wash water by 85% - 90%, and results in significant emission reductions. Economic analysis carried out by using financial indicators such as DSCR, Payback period and IRR reveals very attractive rate of returns and thus, greatly reduces the risks in financing such projects by the financial institutions.
基金supported by the National Science and Technology Major Project (No. 2009ZX07529-004-2)the National High Technology Research and Development Program (863) of China (No. 2009AA063901)
文摘A two-stage UASB reactor was employed to remove sulfate from acrylic fiber manufacturing wastewater.Mesophilic operation（35±0.5℃） was performed with hydraulic retention time（HRT） varied between 28 and 40 hr.Mixed liquor suspended solids（MLSS） in the reactor was maintained about 8000 mg/L.The results indicated that sulfate removal was enhanced with increasing the ratio of COD/SO24-.At low COD/SO42-,the growth of the sulfate-reducing bacteria（SRB） was carbon-limited.The optimal sulfate removal efficiencies were 75% when the HRT was no less than 38 hr.Sulfidogenesis mainly happened in the sulfate-reducing stage,while methanogenesis in the methane-producing stage.Microbes in sulfate-reducing stage performed granulation better than that in methaneproducing stage.Higher extracellular polymeric substances（EPS） content in sulfate-reducing stage helped to adhere and connect the flocculent sludge particles together.SRB accounted for about 31% both in sulfate-reducing stage and methane-producing stage at COD/SO42-ratio of 0.5,while it dropped dramatically from 34% in sulfate-reducing stage to 10% in methane-producing stage corresponding to the COD/SO42-ratio of 4.7.SRB and MPA were predominant in sulfate-reducing stage and methane-producing stage respectively.
基金The authors are grateful to the financial support by National Natural Science Foundation of China(Grant No.51506027)“Young Talents”Project of Northeast Agricultural University(Grant No.16QC18).
文摘The granular sludge of microbial fermentation systems includes various biomass-degrading enzymes and different microflora,which have significant impacts on the degradation of biomass and the stability of the system.An up-flow anaerobic sludge blanket(UASB)reactor was used to grow hydrogen-producing granular sludge.The results showed that the formation of the granular sludge underwent four stages,i.e.,flocculation of the sludge,formation of the flocculent sludge,swelling of the flocculent sludge,and formation of the granular sludge.The formed granular sludge mostly had regular spherical and ellipsoidal shapes with a fractal dimension of 2.08±0.4;the settling velocities were 0.84 cm/s to 1.96 cm/s in water,the porosity was 0.67-0.95.The shear sensitivity(Kss)of the granular sludge was 0.1152.The granular sludge had a culture cycle of approximately 70 d and a hydrogen yield of 1.09 mol H2/mol glucose.
基金Acknowledgements This research was partially supported by the National Science Foundation of China （Grant Nos.51578205 and 51538012）, the Fundamental Research Funds for the Central Universities （No. JZ2016HGTB0722）, and the Program for Cultivating Excellent Talents in Beijing （No. 2013D002020000001）.
文摘Roxarsone （3-nitro-4-hydroxyphenylarsonic acid, ROX） has been widely used for decades as an organoarsenic feed additive to control intestinal parasites and improve feed efficiency in animal production. However, most of the ROX is excreted into the manure, causing arsenic contamination in wastewater. The arsenic compounds are toxic to microorganisms, but the influence of continuous ROX loading on upflow anaerobic sludge blanket （UASB） reactor is still unknown. In this study, the impact of ROX and its degradation products on the performance of the UASB reactor and the degradation and speciation of ROX in the reactor were investigated. The UASB reactor （hydraulic retention time： 1.75 d） was operated using synthetic wastewater supplemented with ROX for a period of 260 days. With continuous ROX addition at 25.0 mg.L-1, severe inhibition to methanogenic activity occurred after 87 days operation accompanied with an accumulation of volatile fatty acids （VFAs） and a decline in pH. The decrease of added ROX concentration to 13.2 mg.L-1 did not mediate the inhibition. As（III）, As （V）, MMA（V）, DMA（V）, HAPA and an unknown arsenic compound were detected in the reactor, and a possible biotransformation pathway of ROX was proposed. Mass balance analysis of arsenic indicated that 60%-70% of the arsenic was discharged into the effluent, and 30%-40% was precipitated in the reactor. The results from this study suggest that we need to pay attention to the stability in the UASB reactors treating organoarsenic-contaminated manure and wastewater, and the effluent and sludge from the reactor tO avoid diffusion of arsenic contamination.
