The effects of chemical oxygen demand and nitrogen(COD/N)ratio and dissolved oxygen concentration(DO)on simultaneous nitrification and denitrification(SND)were investigated using an airlift internal circulation membra...The effects of chemical oxygen demand and nitrogen(COD/N)ratio and dissolved oxygen concentration(DO)on simultaneous nitrification and denitrification(SND)were investigated using an airlift internal circulation membrane bioreactor(AIC-MBR)with synthetic wastewater.The results showed that the COD efficiencies were consistently greater than 90% regardless of changes in the COD/N ratio.At the COD/N ratio of 4.77 and 10.04,the system nitrogen removal efficiency became higher than 70%.However,the nitrogen remova...展开更多
Two parallel carbon-membrane aerated biofilm reactors were operated at well-defined conditions to investigate the effect of substrate COD/N ratios on the performance and microbial community structure of the bioreactor...Two parallel carbon-membrane aerated biofilm reactors were operated at well-defined conditions to investigate the effect of substrate COD/N ratios on the performance and microbial community structure of the bioreactor. Results showed that at substrate COD/N of 5, organic and nitrogen could be eliminated simultaneously, and COD removal degree, nitrification and denitrification efficiency reached 85%, 93% and 92%, respectively. With increasing substrate COD/N ratios, the specific oxygen utilization rates of nitrifying bacteria in biofilm were found to decrease, indicating that nitrifying population became less dominant. At substrate COD/N ratio of 6, excessive heterotrophs inhibited the activity of nitrifying bacteria greatly and thus led to poor nitrification process. With the help of fluorescence in situ hybridization （FISH）, Nitrosomonas and Nitrosospira were identified as dominant ammonia-oxidizing bacteria in the biofilm at substrate COD/N of 0, whereas only Nitrosospira were detected in the biofilm at COD/N ratio of 5. Nitrospira were present as dominant nitrite-oxidizing bacteria in our study. Confocal laser scanning microscopy images revealed that at substrate COD/N ratio of 0 nitrifying bacteria existed throughout the biofilm and that at COD/N ratio of 5 they were mainly distributed in the inner layer of biofilm.展开更多
The effect of COD/N ratio on the granulation process and microbial population succession was investigated.Four identical sequencing batch reactors,R1,R2,R3 and R4,were operated with various initial COD/N ratios rangin...The effect of COD/N ratio on the granulation process and microbial population succession was investigated.Four identical sequencing batch reactors,R1,R2,R3 and R4,were operated with various initial COD/N ratios ranging from 0/200 to 800/200（m/m）.Ethanol was fed as the source of COD.Aerobic granules were successfully cultivated in R2 and R3,operating with the COD/N ratio of 200/200 and 400/200,respectively.Scanning electron microscope observations indicated that short rod-shaped and spherical bacteria were dominant in R2,while granules produced in R3 were surrounded with a large amount of filamentous bacteria.The average specific nitritation rate in R2 and R3 were 0.019 and 0.008 mg N/（mg MLVSS.hr）,respectively.Fluorescence in situ hybridization results demonstrated that nitrifying bacteria population was enriched remarkably in R2.It indicated that nitrification ability and nitrifying bacteria population were enriched remarkably at low COD/N ratio.However,no granules were formed in R1 and R4 which might attribute to either limited or excessive extracellular polymeric substances production.This study contributed to a better understanding of the role of COD/N ratio in nitrifying sludge granulation.展开更多
The impact of the organic carbon to nitrogen ratio （chemical oxygen demand （COD）/N） in wastewater and dissolved oxygen （DO） concentration on carbon and nitrogen removal efficiency, and total bacteria and ammonia...The impact of the organic carbon to nitrogen ratio （chemical oxygen demand （COD）/N） in wastewater and dissolved oxygen （DO） concentration on carbon and nitrogen removal efficiency, and total bacteria and ammonia-oxidizing bacteria （AOB） communities in activated sludge in constantly aerated sequencing batch reactors （SBRs） was determined. At DO of 0.5 and 1.5 mg O2/L during the aeration phase, the efficiency of ammonia oxidation exceeded 90%, with nitrates as the main product. Nitrification and denitrification achieved under the same operating conditions suggested the simultaneous course of these processes. The most effective nitrogen elimination （above 50%） was obtained at the COD/N ratio of 6.8 and DO of 0.5 mg O2/L. Total bacterial diversity was similar in all experimental series, however, for both COD/N ratios of 6.8 and 0.7, higher values were observed at DO of 0.5 mg O2/L. The diversity and abundance of AOB were higher in the reactors with the COD/N ratio of 0.7 in comparison with the reactors with the COD/N of 6.8. For both COD/N ratios applied, the AOB population was not affected by oxygen concentration. Amplicons with sequences indicating membership of the genus Nitrosospira were the determinants of variable technological conditions.展开更多
The effects of increasing COD/N on nitrogen removal performance and microbial structure were investigated in a SBR adopting a completely autotrophic nitrogen removal over nitrite process with a continuous aeration mod...The effects of increasing COD/N on nitrogen removal performance and microbial structure were investigated in a SBR adopting a completely autotrophic nitrogen removal over nitrite process with a continuous aeration mode (DO at approximately 0.15-0.2 mg/L). As the COD/N increased from 0.1 to W0.59, the nitrogen removal efficiency QMRE) increased from 88.7% to 95.5%;while at COD/N ratios of 0.59-0.82, the NRE remained at 90.7%-95.5%. As the COD/N increased from 0.82 to 1.07, the NRE decreased continuously until reaching 60.1%. Nitrosomonas sp.(AOB) and Candidatus Jet tenia (anammox bacteria) were the main functional genera in the SBR. As the COD/N increased from 0.10 to 1.07, the relative abundance of Nitrosomonas decreased from 13.4% to 2.0%, while that of Candidatus Jettenia decreased from 35% to 9.9% with COD/N < 0.82 then increased to 45.4% at a COD/N of 1.07. Aerobic heterotrophic bacteria outcompeted AOB at high COD loadings (650 mg/L) because of oxygen competition, which ultimately led to deteriorated nitrogen removal pertormance.展开更多
文摘The effects of chemical oxygen demand and nitrogen(COD/N)ratio and dissolved oxygen concentration(DO)on simultaneous nitrification and denitrification(SND)were investigated using an airlift internal circulation membrane bioreactor(AIC-MBR)with synthetic wastewater.The results showed that the COD efficiencies were consistently greater than 90% regardless of changes in the COD/N ratio.At the COD/N ratio of 4.77 and 10.04,the system nitrogen removal efficiency became higher than 70%.However,the nitrogen remova...
基金supported by the National Science Council of China (No.50578023)
文摘Two parallel carbon-membrane aerated biofilm reactors were operated at well-defined conditions to investigate the effect of substrate COD/N ratios on the performance and microbial community structure of the bioreactor. Results showed that at substrate COD/N of 5, organic and nitrogen could be eliminated simultaneously, and COD removal degree, nitrification and denitrification efficiency reached 85%, 93% and 92%, respectively. With increasing substrate COD/N ratios, the specific oxygen utilization rates of nitrifying bacteria in biofilm were found to decrease, indicating that nitrifying population became less dominant. At substrate COD/N ratio of 6, excessive heterotrophs inhibited the activity of nitrifying bacteria greatly and thus led to poor nitrification process. With the help of fluorescence in situ hybridization （FISH）, Nitrosomonas and Nitrosospira were identified as dominant ammonia-oxidizing bacteria in the biofilm at substrate COD/N of 0, whereas only Nitrosospira were detected in the biofilm at COD/N ratio of 5. Nitrospira were present as dominant nitrite-oxidizing bacteria in our study. Confocal laser scanning microscopy images revealed that at substrate COD/N ratio of 0 nitrifying bacteria existed throughout the biofilm and that at COD/N ratio of 5 they were mainly distributed in the inner layer of biofilm.
基金supported by the National Key Technologies R&D Program of China during the Eleventh Five-year Plan Period (No. 2009BAC57B01)the State Key Laboratory of Urban Water Resource and Environment(HIT) (No. QAK201006)
文摘The effect of COD/N ratio on the granulation process and microbial population succession was investigated.Four identical sequencing batch reactors,R1,R2,R3 and R4,were operated with various initial COD/N ratios ranging from 0/200 to 800/200（m/m）.Ethanol was fed as the source of COD.Aerobic granules were successfully cultivated in R2 and R3,operating with the COD/N ratio of 200/200 and 400/200,respectively.Scanning electron microscope observations indicated that short rod-shaped and spherical bacteria were dominant in R2,while granules produced in R3 were surrounded with a large amount of filamentous bacteria.The average specific nitritation rate in R2 and R3 were 0.019 and 0.008 mg N/（mg MLVSS.hr）,respectively.Fluorescence in situ hybridization results demonstrated that nitrifying bacteria population was enriched remarkably in R2.It indicated that nitrification ability and nitrifying bacteria population were enriched remarkably at low COD/N ratio.However,no granules were formed in R1 and R4 which might attribute to either limited or excessive extracellular polymeric substances production.This study contributed to a better understanding of the role of COD/N ratio in nitrifying sludge granulation.
文摘The impact of the organic carbon to nitrogen ratio （chemical oxygen demand （COD）/N） in wastewater and dissolved oxygen （DO） concentration on carbon and nitrogen removal efficiency, and total bacteria and ammonia-oxidizing bacteria （AOB） communities in activated sludge in constantly aerated sequencing batch reactors （SBRs） was determined. At DO of 0.5 and 1.5 mg O2/L during the aeration phase, the efficiency of ammonia oxidation exceeded 90%, with nitrates as the main product. Nitrification and denitrification achieved under the same operating conditions suggested the simultaneous course of these processes. The most effective nitrogen elimination （above 50%） was obtained at the COD/N ratio of 6.8 and DO of 0.5 mg O2/L. Total bacterial diversity was similar in all experimental series, however, for both COD/N ratios of 6.8 and 0.7, higher values were observed at DO of 0.5 mg O2/L. The diversity and abundance of AOB were higher in the reactors with the COD/N ratio of 0.7 in comparison with the reactors with the COD/N of 6.8. For both COD/N ratios applied, the AOB population was not affected by oxygen concentration. Amplicons with sequences indicating membership of the genus Nitrosospira were the determinants of variable technological conditions.
基金the National Natural Science Foundation of China (Grant Nos. 51522809 and 51378370)the State Key Laboratory of Pollution Control and Resource Reuse (Tongji University), China (Grant No. PCRRT16005).
文摘The effects of increasing COD/N on nitrogen removal performance and microbial structure were investigated in a SBR adopting a completely autotrophic nitrogen removal over nitrite process with a continuous aeration mode (DO at approximately 0.15-0.2 mg/L). As the COD/N increased from 0.1 to W0.59, the nitrogen removal efficiency QMRE) increased from 88.7% to 95.5%;while at COD/N ratios of 0.59-0.82, the NRE remained at 90.7%-95.5%. As the COD/N increased from 0.82 to 1.07, the NRE decreased continuously until reaching 60.1%. Nitrosomonas sp.(AOB) and Candidatus Jet tenia (anammox bacteria) were the main functional genera in the SBR. As the COD/N increased from 0.10 to 1.07, the relative abundance of Nitrosomonas decreased from 13.4% to 2.0%, while that of Candidatus Jettenia decreased from 35% to 9.9% with COD/N < 0.82 then increased to 45.4% at a COD/N of 1.07. Aerobic heterotrophic bacteria outcompeted AOB at high COD loadings (650 mg/L) because of oxygen competition, which ultimately led to deteriorated nitrogen removal pertormance.
