Three identical membrane bioreactors （MBRs） were operated over 2 years at different sludge retention time （SRT） of 10 d, 40 d and no sludge withdrawal （NS）, to elucidate and quantify the effect of SRT on the slu...Three identical membrane bioreactors （MBRs） were operated over 2 years at different sludge retention time （SRT） of 10 d, 40 d and no sludge withdrawal （NS）, to elucidate and quantify the effect of SRT on the sludge characteristics and membrane fouling. The hydraulic retention times of these MBRs were controlled at 12 h. With increasing SRT, the sludge concentrations in the MBRs increased, whereas the ratio of volatile suspended solid to the total solid decreased, and the size of sludge granule diminished in the meantime. A higher sludge concentration at long SRT could maintain a better organic removal efficiency, and a longer SRT was propitious to the growth of nitrifiers. The performance of these MBRs for the removal of COD and NH4^＋-N did not change much with different SRTs. However, the bioactivity decreased as SRT increase. The measurement of specific oxygen uptake rates （SOUR） and fluorescence in situ hybridization （FISH） with rRNA-targeted oligonucleotide probes testified that SOUR and the proportion of the bacteria-specific probe EUB338 in all DAPI-stainable bacteria decreased with increasing SRT. The concentrations of total organic carbon, protein, polysaccharides and soluble extracellular polymeric substance （EPS） in the mixed liquor supernatant also decreased with increasing SRT. The membrane fouling rate was higher at shorter SRT, and the highest fouling rate appeared at a SRT of 10 d. Both the sludge cake layer and gel layer had contribution to the fouling resistance, but the relative contribution of the gel layer decreased as SRT increase.展开更多
Effect of sludge retention time( SRT) on the removal of potential and polysaccharides in an anaerobic / anoxic / aerobic( AAO) process was investigated. The Lowry method and anthrone method were used to detect protein...Effect of sludge retention time( SRT) on the removal of potential and polysaccharides in an anaerobic / anoxic / aerobic( AAO) process was investigated. The Lowry method and anthrone method were used to detect proteins and polysaccharides. Total removal efficiency of proteins at SRT of 10 to 25 d in the AAO system was higher than 90%. Polysaccharides removal efficiencies were above 80% when SRT was increased from 15 to 25 d,whereas only 81% of polysaccharides was removed at SRT of 10 d. The biodegradation part of proteins and polysaccharides increased from87. 40% to 93% and from 74. 22% to 86. 94% with increasing SRTs.The ratios of polysaccharides and proteins in extracellular polymer substances( EPSs) were around 1. 5-3 in different SRTs. As SRT increasing,polysaccharides and proteins discharged with residual sludge decreased gradually. The amount of EPSs decreased with increasing SRTs.展开更多
Four sequence batch reactors（SBRs） fed by fermented sugar cane wastewater were continuously operated under the aerobic dynamic feeding（ADF） mode with different configurations of sludge retention time（SRT）, carbo...Four sequence batch reactors（SBRs） fed by fermented sugar cane wastewater were continuously operated under the aerobic dynamic feeding（ADF） mode with different configurations of sludge retention time（SRT）, carbon and initial biomass concentrations to enrich polyhydroxyalkanoate（PHA） accumulating mixed microbial cultures（MMCs） from municipal activated sludge.The stability of SBRs was investigated besides the enrichment performance. The microbial community structures of the enriched MMCs were analyzed using terminal restriction fragment length polymorphism（T-RFLP）. The optimum operating conditions for the enrichment process were： SRT of 5 days, carbon concentration of 2.52 g COD/L and initial biomass concentration of3.65 g/L. The best enrichment performance in terms of both operating stability and PHA storage ability of enriched cultures（with the maximum PHA content and PHA storage yield（YPHA/S） of61.26% and 0.68 mg COD/mg COD, respectively） was achieved under this condition. Effects of the SRT, carbon concentration and initial biomass concentration on the PHA accumulating MMCs selection process were discussed respectively. A new model including the segmentation of the enrichment process and the effects of SRT on each phase was proposed.展开更多
Here the effect of solid retention time(SRT) on the concentration of the mixed liquor suspend solid(MLSS),the sludge characteristics,the content of extra-cellular polymeric substances(EPS),the viscosity of mixed liquo...Here the effect of solid retention time(SRT) on the concentration of the mixed liquor suspend solid(MLSS),the sludge characteristics,the content of extra-cellular polymeric substances(EPS),the viscosity of mixed liquor and effluent quality in the immersed membrane bioreactor(IMBR) was investi-gated.The results indicate that the increase of the EPS content is the main reason for the increase of mixed liquor viscosity,the former is positively correlated with the latter(R2 = 0.9751).The size distribution profile of particles in the mixed liquor presents double-peak shape at SRT more than 30 days.The filtration resistance of membrane in IMBR is mainly caused by the tiny particles and the viscosity of the mixed liquor.In this study,the extension of SRT can hardly affect the removal efficiency of Chemical Oxygen Demand(COD) and NH+4―N,and when SRT is below 30 days,silt density index(SDI15) is less than 3,the effluent can be deeply treated by using reverse osmosis system(RO) or nano-filtration system(NF).The method of controlling SRT is put forward by analyzing the relationship between SRT and the minimum generation-time of dominant bacteria(at the maximum specific growth rate under the operation temperature).展开更多
The study was conducted to investigate the effect of sludge retention on bacterial community composition of membrane bioreactor(MBR)treating synthetic hospital wastewater.The removal of four pharmaceuticals,namely car...The study was conducted to investigate the effect of sludge retention on bacterial community composition of membrane bioreactor(MBR)treating synthetic hospital wastewater.The removal of four pharmaceuticals,namely carbamazepine,estradiol,venlafaxine,and ibuprofen in MBR,was studied at varying sludge retention time(SRT)duration of 100,45,and 15 days and hydraulic retention time(HRT)of 18 h.The removal of ibuprofen and estradiol was constant at varying SRT;however,a negligible removal of carbamazepine and low removal of venlafaxine was observed(<20%).The study suggested that the SRT of 45 days in MBR could provide maximum treatment efficiency via decreasing membrane clogging.The effect of sludge age and pharmaceutical presence on the bacterial community was investigated via high-throughput sequencing.The study reveals that the variation in SRT affects the dynamics of the bacterial community significantly.For instance,the dominant bacterium Caldimonas of SRT 100 was disappeared at lower SRTs.Moreover,the profile of the dominant genus of the SRTs varied greatly from each other.展开更多
A bench-scale anaerobic/anoxic/aerobic process-biological aerated filter （A^2/O-BAF） combined system was carded out to treat wastewater with lower C/N and C/P ratios. The A^2/O process was operated in a short aerobi...A bench-scale anaerobic/anoxic/aerobic process-biological aerated filter （A^2/O-BAF） combined system was carded out to treat wastewater with lower C/N and C/P ratios. The A^2/O process was operated in a short aerobic sludge retention time （SRT） for organic pollutants and phosphorus removal, and denitrification. The subsequent BAF process was mainly used for nitrification. The BAF effluent was partially returned to anoxic zone of the A^2/O process to provide electron acceptors for denitrification and anoxic P uptake. This unique system formed an environment for reproducing the denitdfying phosphate-accumulating organisms （DPAOs）. The ratio of DPAOs to phosphorus accumulating organisms （PAOs） could be maintained at 28% by optimizing the organic loads in the anaerobic zone and the nitrate loads into the anoxic zone in the A^2/O process. The aerobic phosphorus over-uptake and discharge of excess activated sludge was the main mechanism of phosphorus removal in the combined system. The aerobic SRT of the A^2/O process should meet the demands for the development of aerobic PAOs and the restraint on the nitrifiers growth, and the contact time in the aerobic zone of the A^2/O process should be longer than 30 min, which ensured efficient phosphorus removal in the combined system. The adequate BAF effluent return rates should be controlled with 1--4 mg/L nitrate nitrogen in the anoxic zone effluent of A^2/O process to achieve the optimal nitrogen and phosphorus removal efficiencies.展开更多
基金supported by the National Natural Science Foundation of China (No 50678170)
文摘Three identical membrane bioreactors （MBRs） were operated over 2 years at different sludge retention time （SRT） of 10 d, 40 d and no sludge withdrawal （NS）, to elucidate and quantify the effect of SRT on the sludge characteristics and membrane fouling. The hydraulic retention times of these MBRs were controlled at 12 h. With increasing SRT, the sludge concentrations in the MBRs increased, whereas the ratio of volatile suspended solid to the total solid decreased, and the size of sludge granule diminished in the meantime. A higher sludge concentration at long SRT could maintain a better organic removal efficiency, and a longer SRT was propitious to the growth of nitrifiers. The performance of these MBRs for the removal of COD and NH4^＋-N did not change much with different SRTs. However, the bioactivity decreased as SRT increase. The measurement of specific oxygen uptake rates （SOUR） and fluorescence in situ hybridization （FISH） with rRNA-targeted oligonucleotide probes testified that SOUR and the proportion of the bacteria-specific probe EUB338 in all DAPI-stainable bacteria decreased with increasing SRT. The concentrations of total organic carbon, protein, polysaccharides and soluble extracellular polymeric substance （EPS） in the mixed liquor supernatant also decreased with increasing SRT. The membrane fouling rate was higher at shorter SRT, and the highest fouling rate appeared at a SRT of 10 d. Both the sludge cake layer and gel layer had contribution to the fouling resistance, but the relative contribution of the gel layer decreased as SRT increase.
基金National Natural Science Foundations of China(Nos.21477018,21007010)Hunan Province Ministry of Transportation Scientific Research Projects,China(Nos.200908,201105)Ministry of Transport Science and Technology Program,China(No.2010353343290)
文摘Effect of sludge retention time( SRT) on the removal of potential and polysaccharides in an anaerobic / anoxic / aerobic( AAO) process was investigated. The Lowry method and anthrone method were used to detect proteins and polysaccharides. Total removal efficiency of proteins at SRT of 10 to 25 d in the AAO system was higher than 90%. Polysaccharides removal efficiencies were above 80% when SRT was increased from 15 to 25 d,whereas only 81% of polysaccharides was removed at SRT of 10 d. The biodegradation part of proteins and polysaccharides increased from87. 40% to 93% and from 74. 22% to 86. 94% with increasing SRTs.The ratios of polysaccharides and proteins in extracellular polymer substances( EPSs) were around 1. 5-3 in different SRTs. As SRT increasing,polysaccharides and proteins discharged with residual sludge decreased gradually. The amount of EPSs decreased with increasing SRTs.
基金supported by the National Natural Science Foundation of China(No.51378142)the Program for New Century Excellent Talents in University(No.NCET-12-0156)+1 种基金the Open Project of the State Key Laboratory of Urban Water ResourceEnvironment(Harbin institute of Technology)(No.2015DX10)
文摘Four sequence batch reactors（SBRs） fed by fermented sugar cane wastewater were continuously operated under the aerobic dynamic feeding（ADF） mode with different configurations of sludge retention time（SRT）, carbon and initial biomass concentrations to enrich polyhydroxyalkanoate（PHA） accumulating mixed microbial cultures（MMCs） from municipal activated sludge.The stability of SBRs was investigated besides the enrichment performance. The microbial community structures of the enriched MMCs were analyzed using terminal restriction fragment length polymorphism（T-RFLP）. The optimum operating conditions for the enrichment process were： SRT of 5 days, carbon concentration of 2.52 g COD/L and initial biomass concentration of3.65 g/L. The best enrichment performance in terms of both operating stability and PHA storage ability of enriched cultures（with the maximum PHA content and PHA storage yield（YPHA/S） of61.26% and 0.68 mg COD/mg COD, respectively） was achieved under this condition. Effects of the SRT, carbon concentration and initial biomass concentration on the PHA accumulating MMCs selection process were discussed respectively. A new model including the segmentation of the enrichment process and the effects of SRT on each phase was proposed.
基金Supported by Natural Science Foundation of Tianjin (Grant No.08JC2DJC24300)
文摘Here the effect of solid retention time(SRT) on the concentration of the mixed liquor suspend solid(MLSS),the sludge characteristics,the content of extra-cellular polymeric substances(EPS),the viscosity of mixed liquor and effluent quality in the immersed membrane bioreactor(IMBR) was investi-gated.The results indicate that the increase of the EPS content is the main reason for the increase of mixed liquor viscosity,the former is positively correlated with the latter(R2 = 0.9751).The size distribution profile of particles in the mixed liquor presents double-peak shape at SRT more than 30 days.The filtration resistance of membrane in IMBR is mainly caused by the tiny particles and the viscosity of the mixed liquor.In this study,the extension of SRT can hardly affect the removal efficiency of Chemical Oxygen Demand(COD) and NH+4―N,and when SRT is below 30 days,silt density index(SDI15) is less than 3,the effluent can be deeply treated by using reverse osmosis system(RO) or nano-filtration system(NF).The method of controlling SRT is put forward by analyzing the relationship between SRT and the minimum generation-time of dominant bacteria(at the maximum specific growth rate under the operation temperature).
基金The authors thank the Natural Sciences and Engineering Research Council of Canada,Canada(NSERC-STPGP-479160 Strategic grant,Premier Tech Ltée,Canada Research Chair)for financial support.
文摘The study was conducted to investigate the effect of sludge retention on bacterial community composition of membrane bioreactor(MBR)treating synthetic hospital wastewater.The removal of four pharmaceuticals,namely carbamazepine,estradiol,venlafaxine,and ibuprofen in MBR,was studied at varying sludge retention time(SRT)duration of 100,45,and 15 days and hydraulic retention time(HRT)of 18 h.The removal of ibuprofen and estradiol was constant at varying SRT;however,a negligible removal of carbamazepine and low removal of venlafaxine was observed(<20%).The study suggested that the SRT of 45 days in MBR could provide maximum treatment efficiency via decreasing membrane clogging.The effect of sludge age and pharmaceutical presence on the bacterial community was investigated via high-throughput sequencing.The study reveals that the variation in SRT affects the dynamics of the bacterial community significantly.For instance,the dominant bacterium Caldimonas of SRT 100 was disappeared at lower SRTs.Moreover,the profile of the dominant genus of the SRTs varied greatly from each other.
文摘A bench-scale anaerobic/anoxic/aerobic process-biological aerated filter （A^2/O-BAF） combined system was carded out to treat wastewater with lower C/N and C/P ratios. The A^2/O process was operated in a short aerobic sludge retention time （SRT） for organic pollutants and phosphorus removal, and denitrification. The subsequent BAF process was mainly used for nitrification. The BAF effluent was partially returned to anoxic zone of the A^2/O process to provide electron acceptors for denitrification and anoxic P uptake. This unique system formed an environment for reproducing the denitdfying phosphate-accumulating organisms （DPAOs）. The ratio of DPAOs to phosphorus accumulating organisms （PAOs） could be maintained at 28% by optimizing the organic loads in the anaerobic zone and the nitrate loads into the anoxic zone in the A^2/O process. The aerobic phosphorus over-uptake and discharge of excess activated sludge was the main mechanism of phosphorus removal in the combined system. The aerobic SRT of the A^2/O process should meet the demands for the development of aerobic PAOs and the restraint on the nitrifiers growth, and the contact time in the aerobic zone of the A^2/O process should be longer than 30 min, which ensured efficient phosphorus removal in the combined system. The adequate BAF effluent return rates should be controlled with 1--4 mg/L nitrate nitrogen in the anoxic zone effluent of A^2/O process to achieve the optimal nitrogen and phosphorus removal efficiencies.
