A lab-scale anaerobic-anoxic-oxic (A2O) process used to treat a synthetic brewage wastewater was investigated. The objectives of the study were to identify the existence of denitrifying phosphorus removing bacteria (D...A lab-scale anaerobic-anoxic-oxic (A2O) process used to treat a synthetic brewage wastewater was investigated. The objectives of the study were to identify the existence of denitrifying phosphorus removing bacteria (DPB), evaluate the contribution of DPB to biological nutrient removal and enhance the denitrifying phosphorus removal in A2O bioreactors. Sludge analysis confirmed that the average anoxic P uptake accounted for approximately 70% the total amount of P uptake, and the ratio of anoxic P uptake rate to aerobic P uptake rate was 69%. In addition, nitrate concentration in the anoxic phase and different organic substrate introduced into the anaerobic phase had significant effect on the anoxic P uptake. Compared with conventional A2O processes, good removal efficiencies of COD, phosphorus, ammonia and total nitrogen (92.3%, 95.5%, 96% and 79.5%, respectively) could be achieved in the anoxic P uptake system, and aeration energy consumption was saved 25%. By controlling the nitrate recirculation flow in the anoxic zone, anoxic P uptake could be enhanced, which solved the competition for organic substrates among poly-P organisms and denitrifiers successfully under the COD limiting conditions. Therefore, in wastewater treatment plants the control system should be applied according to the practical situation to optimize the operation.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
YBa2Cu3O7-δ-Agx composite superconductors were prepared by hybrid sintering process using YBa2Cu3O7-δ-Agx ultrafine powder and Ag2O finepower, which were prepared by sol-gel process and precipitation process respect...YBa2Cu3O7-δ-Agx composite superconductors were prepared by hybrid sintering process using YBa2Cu3O7-δ-Agx ultrafine powder and Ag2O finepower, which were prepared by sol-gel process and precipitation process respectively. The effect of the Ag content on superconducting crictical transition temperature of YBa2Cu3O7-δ-Agx was not evident as long as YBa2Cu3O7-δ-Agx can form continuous network. But Ag can increase superconduction crictical current and density of the composite superconductors. The normal state (i.e. non-superconducting state at room temperature) resistivity shows a percolation threshold at 20%-30% Ag, whereas the superconducting net-work shows a percolationthreshold at 70% -80% Ag.展开更多
Objective This study was conducted to optimize the operational parameters of anaerobic-anoxic-oxic （A^2/O） processes to reduce the toxicity of municipal wastewater and evaluate its ability to reduce toxicity. Method...Objective This study was conducted to optimize the operational parameters of anaerobic-anoxic-oxic （A^2/O） processes to reduce the toxicity of municipal wastewater and evaluate its ability to reduce toxicity. Methods A luminescent bacterium toxicity bioassay was employed to assess the toxicity of influent and effluent of each reactor in the A2/O system. Results The optimum operational parameters for toxicity reduction were as follows： anaerobic hydraulic retention time （HRT） = 2.8 h, anoxic HRT = 2.8 h, aerobic HRT = 6.9 h, sludge retention time （SRT） = 15 days and internal recycle ratio （IRR） = 100%. An important toxicity reduction （%） was observed in the optimized A2/O process, even when the toluene concentration of the influent was 120.7 mg·L^-1. Conclusions The toxicity of municipal wastewater was reduced significantly during the A^2/O process. A^2/O process can be used for toxicity reduction of municipal wastewater under toxic-shock loading.展开更多
This study evaluated the removal of multiple pollutants,i.e.,polybrominated diphenyl ethers(PBDEs),novel halogenated flame retardants(HFRs),sulfonamide antibiotics(SAs),and heavy metals(HMs),by a fullscale reversed A^...This study evaluated the removal of multiple pollutants,i.e.,polybrominated diphenyl ethers(PBDEs),novel halogenated flame retardants(HFRs),sulfonamide antibiotics(SAs),and heavy metals(HMs),by a fullscale reversed A^(2)/O process in a sewage treatment plant(STP)in Guangzhou,China.The reversed A^(2)/O process demonstrated high removal efficiencies(REs)for total PBDEs(60.5%±4.3%),novel HFRs(98.4%±2.8%)and HMs(70.1%±1.2%),and a relatively low RE for SAs(25.0%±2.3%).BDE 209,the dominant PBDE congener,showed a high residual concentration(13.41±5.18 ng/L)in the suspended particulate matter(SPM)of treated effluents.So me novel HFRs,dechlorane plus(DP)and decabromodiphe nyl ethane(DBDPE),were detected in the SPM of the raw sewage(7.50±4.14 ng/L and 11.52±11.65 ng/L,respectively).The removal ofSAs was mainly through biodegradation in the activated sludge bioreactors(ASBs).Ofthe HMs,Mn and Ni exhibited the lowest REs(47.5%±2.2%and 35.0%±2.6%,respectively),while Cr and Cu showed the highest removal(REs>80%).In terms of treatment units in the reversed A^(2)/O process,ASBs showed the highest RE(27.8%)for the multiple pollutants.The information can aid in our understanding of removal properties of STPs on various pollutants and evaluating the ecological/health risks of STPs as point pollutant sources.展开更多
In this study,an anaerobic/anoxic/oxic(A^(2)O)wastewater treatment process was implemented to treat domestic wastewater with short-term atrazine addition.The results provided an evaluation on the effects of an acciden...In this study,an anaerobic/anoxic/oxic(A^(2)O)wastewater treatment process was implemented to treat domestic wastewater with short-term atrazine addition.The results provided an evaluation on the effects of an accidental pollution on the operation of a wastewater treatment plant(WWTP)in relation to Chemical Oxygen Demand(COD)and biological nutrient removal.Domestic wastewater with atrazine addition in 3 continuous days was treated when steady biological nutrient removal was achieved in the A^(2)O process.The concentrations of atrazine were 15,10,and 5 mg%L–1 on days 1,2 and 3,respectively.The results showed that atrazine addition did not affect the removal of COD.The specific NH4þoxidation rate and NO3–reduction rate decreased slightly due to the short-term atrazine addition.However,it did not affect the nitrogen removal due to the high nitrification and denitrification capacity of the system.Total nitrogen(TN)removal was steady,and more than 70%was removed during the period studied.The phosphorus removal rate was not affected by the short-term addition of atrazine under the applied experimental conditions.However,more poly-hydroxy-alkanoate(PHA)was generated and utilized during atrazine addition.The results of the oxygen uptake rate(OUR)showed that the respiration of nitrifiers decreased significantly,while the activity of carbon utilizers had no obvious change with the atrazine addition.Atrazine was not removed with the A^(2)O process,even via absorption by the activated sludge in the process of the short-term addition of atrazine.展开更多
基金Supported by Key Technology Research and Development Program of the Tenthfive-year plan (2001BA610A-09), the NationalNatural Science Foundation of China (No. 50478040) and 863 Hi-Technology Research and Development Program of China(No.2004AA601020)
文摘A lab-scale anaerobic-anoxic-oxic (A2O) process used to treat a synthetic brewage wastewater was investigated. The objectives of the study were to identify the existence of denitrifying phosphorus removing bacteria (DPB), evaluate the contribution of DPB to biological nutrient removal and enhance the denitrifying phosphorus removal in A2O bioreactors. Sludge analysis confirmed that the average anoxic P uptake accounted for approximately 70% the total amount of P uptake, and the ratio of anoxic P uptake rate to aerobic P uptake rate was 69%. In addition, nitrate concentration in the anoxic phase and different organic substrate introduced into the anaerobic phase had significant effect on the anoxic P uptake. Compared with conventional A2O processes, good removal efficiencies of COD, phosphorus, ammonia and total nitrogen (92.3%, 95.5%, 96% and 79.5%, respectively) could be achieved in the anoxic P uptake system, and aeration energy consumption was saved 25%. By controlling the nitrate recirculation flow in the anoxic zone, anoxic P uptake could be enhanced, which solved the competition for organic substrates among poly-P organisms and denitrifiers successfully under the COD limiting conditions. Therefore, in wastewater treatment plants the control system should be applied according to the practical situation to optimize the operation.
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.
文摘YBa2Cu3O7-δ-Agx composite superconductors were prepared by hybrid sintering process using YBa2Cu3O7-δ-Agx ultrafine powder and Ag2O finepower, which were prepared by sol-gel process and precipitation process respectively. The effect of the Ag content on superconducting crictical transition temperature of YBa2Cu3O7-δ-Agx was not evident as long as YBa2Cu3O7-δ-Agx can form continuous network. But Ag can increase superconduction crictical current and density of the composite superconductors. The normal state (i.e. non-superconducting state at room temperature) resistivity shows a percolation threshold at 20%-30% Ag, whereas the superconducting net-work shows a percolationthreshold at 70% -80% Ag.
基金supported by the National Science Foundation Project grants of China(No.50878165,No.21007010)the Program for New Century Excellent Talents in University(NCET-08-0403)+4 种基金the Research Fund for the Doctoral Program of Higher Education of China(No.20090075120007)the Shanghai Committee of Science and Technology,China(No.09230500200)the Fundamental Research Funds for the Central Universities of China(No.10D11308)the Key Special Program on the S&T for the Pollution Control and Treatment of Water Bodies(No. 2008ZX07316-003)the Shanghai Leading Academic Discipline Project (No.B604)
文摘Objective This study was conducted to optimize the operational parameters of anaerobic-anoxic-oxic （A^2/O） processes to reduce the toxicity of municipal wastewater and evaluate its ability to reduce toxicity. Methods A luminescent bacterium toxicity bioassay was employed to assess the toxicity of influent and effluent of each reactor in the A2/O system. Results The optimum operational parameters for toxicity reduction were as follows： anaerobic hydraulic retention time （HRT） = 2.8 h, anoxic HRT = 2.8 h, aerobic HRT = 6.9 h, sludge retention time （SRT） = 15 days and internal recycle ratio （IRR） = 100%. An important toxicity reduction （%） was observed in the optimized A2/O process, even when the toluene concentration of the influent was 120.7 mg·L^-1. Conclusions The toxicity of municipal wastewater was reduced significantly during the A^2/O process. A^2/O process can be used for toxicity reduction of municipal wastewater under toxic-shock loading.
基金the National Natural Science Foundation of China(No.91851110)Guangzhou University’s 2017 Training Program for Young Top-Notch Personnels(No.BJ201713)+1 种基金Scientific Research Project of Guangzhou University(No.YK2020017)Guizhou Provincial Department of Education Youth Science and Technology Talents Growth Project(No.KY[2017]300)。
文摘This study evaluated the removal of multiple pollutants,i.e.,polybrominated diphenyl ethers(PBDEs),novel halogenated flame retardants(HFRs),sulfonamide antibiotics(SAs),and heavy metals(HMs),by a fullscale reversed A^(2)/O process in a sewage treatment plant(STP)in Guangzhou,China.The reversed A^(2)/O process demonstrated high removal efficiencies(REs)for total PBDEs(60.5%±4.3%),novel HFRs(98.4%±2.8%)and HMs(70.1%±1.2%),and a relatively low RE for SAs(25.0%±2.3%).BDE 209,the dominant PBDE congener,showed a high residual concentration(13.41±5.18 ng/L)in the suspended particulate matter(SPM)of treated effluents.So me novel HFRs,dechlorane plus(DP)and decabromodiphe nyl ethane(DBDPE),were detected in the SPM of the raw sewage(7.50±4.14 ng/L and 11.52±11.65 ng/L,respectively).The removal ofSAs was mainly through biodegradation in the activated sludge bioreactors(ASBs).Ofthe HMs,Mn and Ni exhibited the lowest REs(47.5%±2.2%and 35.0%±2.6%,respectively),while Cr and Cu showed the highest removal(REs>80%).In terms of treatment units in the reversed A^(2)/O process,ASBs showed the highest RE(27.8%)for the multiple pollutants.The information can aid in our understanding of removal properties of STPs on various pollutants and evaluating the ecological/health risks of STPs as point pollutant sources.
基金the National Key Science and Technology Special Projects(No.2008ZX07209-003)Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality(No.PHR20090502).
文摘In this study,an anaerobic/anoxic/oxic(A^(2)O)wastewater treatment process was implemented to treat domestic wastewater with short-term atrazine addition.The results provided an evaluation on the effects of an accidental pollution on the operation of a wastewater treatment plant(WWTP)in relation to Chemical Oxygen Demand(COD)and biological nutrient removal.Domestic wastewater with atrazine addition in 3 continuous days was treated when steady biological nutrient removal was achieved in the A^(2)O process.The concentrations of atrazine were 15,10,and 5 mg%L–1 on days 1,2 and 3,respectively.The results showed that atrazine addition did not affect the removal of COD.The specific NH4þoxidation rate and NO3–reduction rate decreased slightly due to the short-term atrazine addition.However,it did not affect the nitrogen removal due to the high nitrification and denitrification capacity of the system.Total nitrogen(TN)removal was steady,and more than 70%was removed during the period studied.The phosphorus removal rate was not affected by the short-term addition of atrazine under the applied experimental conditions.However,more poly-hydroxy-alkanoate(PHA)was generated and utilized during atrazine addition.The results of the oxygen uptake rate(OUR)showed that the respiration of nitrifiers decreased significantly,while the activity of carbon utilizers had no obvious change with the atrazine addition.Atrazine was not removed with the A^(2)O process,even via absorption by the activated sludge in the process of the short-term addition of atrazine.
