Residual ammonium is a critical parameter affecting the stability of mainstream partial nitritation/anammox(PN/A), but the underlying mechanism remains unclear. In this study,mainstream PN/A was established and operat...Residual ammonium is a critical parameter affecting the stability of mainstream partial nitritation/anammox(PN/A), but the underlying mechanism remains unclear. In this study,mainstream PN/A was established and operated with progressively decreasing residual ammonium. PN/A deteriorated as the residual ammonium decreased to below 5 mg/L, and this was paralleled by a significant loss in anammox activity in situ and an increasing nitrite oxidation rate. Further analysis revealed that the low-ammonium condition directly decreased anammox activity in situ via two distinct mechanisms. First, anammox bacteria were located in the inner layer of the granular sludge, and thus were disadvantageous when competing for ammonium with ammonium-oxidizing bacteria(AOB) in the outer layer. Second, the complete ammonia oxidizer(comammox) was enriched at low residual ammonium concentrations because of its high ammonium affinity. Both AOB and comammox presented kinetic advantages over anammox bacteria. At high residual ammonium concentrations,nitrite-oxidizing bacteria(NOB) were effectively suppressed, even when their maximum activity was high due to competition for nitrite with anammox bacteria. At low residual ammonium concentrations, the decrease in anammox activity in situ led to an increase in nitrite availability for nitrite oxidation, facilitating the activation of NOB despite the dissolved oxygen limitation(0.15–0.35 mg/L) for NOB persisting throughout the operation. Therefore, the deterioration of mainstream PN/A at low residual ammonium was primarily triggered by a decline in anammox activity in situ. This study provides novel insights into the optimized design of mainstream PN/As in engineering applications.展开更多
Anaerobic ammonium oxidation （ANAMMOX） technology has potential technical superiority and economical efficiency for the nitrogen removal from landfill leachate, which contains high-strength ammonium nitrogen （NH4^...Anaerobic ammonium oxidation （ANAMMOX） technology has potential technical superiority and economical efficiency for the nitrogen removal from landfill leachate, which contains high-strength ammonium nitrogen （NH4^＋-N） and refractory organics. To complete the ANAMMOX process, a preceding partial nitritation step to produce the appropriate ratio of nitrite/ammonium is a key stage. The objective of this study was to determine the optimal conditions to acquire constant partial nitritation for landfill leachate treatment, and a bench scale fixed bed bio-film reactor was used in this study to investigate the effects of the running factors on the partial nitritation. The results showed that both the dissolved oxygen （DO） concentration and the ammonium volumetric loading rate （Nv） had effects on the partial nitritation. In the controlling conditions with a temperature of 30±1℃, Nv of 0.2-1.0 kg NH4＋-N/（m^3·d）, and DO concentration of 0.8-2.3 mg/L, the steady partial nitritation was achieved as follows： more than 94% partial nitritation efficiency （nitrite as the main product）, 60%-74% NH4^＋-N removal efficiency, and NO2^--N/NH4^＋-N ratio （concentration ratio） of 1.0-1.4 in the effluent.The impact of temperature was related to Nv at certain DO concentration, and the temperature range of 25-30℃ was suitable for treating high strength ammonium leachate. Ammonium-oxidizing bacteria （AOB） could be acclimated to higher FA （free ammonium） in the range of 122-224 mg/L. According to the denaturing gradient gel electrophoresis analysis result of the bio-film in the reactor, there were 25 kinds of 16S rRNA gene fragments, which indicated that abundant microbial communities existed in the bio-film, although high concentrations of ammonium and FA may inhibit the growth of the nitrite-oxidizing bacteria （NOB） and other microorganisms in the reactor.展开更多
This study employed multispectral techniques to evaluate fulvic acid(FA)compositional characteristic and elucidate its biodegradation mechanisms during partial nitritation(PN)process.Results showed that FA removal eff...This study employed multispectral techniques to evaluate fulvic acid(FA)compositional characteristic and elucidate its biodegradation mechanisms during partial nitritation(PN)process.Results showed that FA removal efficiency(FRE)decreased from 90.22 to 23.11%when FA concentrations in the reactor were increased from 0 to 162.30 mg/L,and that molecular size,degree of aromatization and humification of the effluent FA macromolecules all increased after treatment.Microbial population analysis indicated that the proliferation of the Comamonas,OLB12 and Thauera exhibit high FA utilization capacity in lower concentrations(<50.59 mg/L),promoting the degradation and removal of macromolecular FA.In addition,the sustained increase in external FA may decrease the abundance of above functional microorganisms,resulting in a rapid drop in FRE.Furthermore,from the genetic perspective,the elevated FA levels restricted carbohydrate(ko00620,ko00010 and ko00020)and nitrogen(HAO,AMO,NIR and NOR)metabolism-related pathways,thereby impeding FA removal and total nitrogen loss associated with N_(2)O emissions.展开更多
Anammox is widely considered as the most cost-effective and sustainable process for nitrogen removal.However,how to achieve the enrichment of anammox biomass remains a challenge for its large-scale application,especia...Anammox is widely considered as the most cost-effective and sustainable process for nitrogen removal.However,how to achieve the enrichment of anammox biomass remains a challenge for its large-scale application,especially in mainstream wastewater treatment.In this study,the feasibility of enrichment of anammox biomass was explored through the realization of partial denitrification and the addition of bio-carriers.By using ordinary activated sludge,a sequencing batch reactor(SBR)followed by an up-fow anaerobic sludge bed(UASB)was operated at 25±2℃ for 214 days.The long-term operation was divided into five phases,in which SBR and UASB were started-up in Phases I and II,respectively.By eliminating oxygen and adjusting the infow ratios in Phases III-V,advanced nitrogen removal was achieved with the effuent total nitrogen being 4.7 mg/L and the nitrogen removal efficiency being 90.5%in Phase V.Both in-situ and ex-situ activity tests demonstrated the occurrence of partial denitrification and anammox.Moreover,16S rRNA high-throughput sequencing analysis revealed that Candidatus Brocadia was enriched from below the detection limit to in biofilms(0.4%in SBR,2.2%in UASB)and the foc sludge(0.2%in SBR,1.3%in UASB),while Thauera was mainly detected in the foc sludge(8.1%in SBR,8.8%in UASB),which might play a key role in partial denitrification.Overall,this study provides a novel strategy to enrich anammox biomass driven by rapid achievement of partial denitrification through the addition of bio-carriers,which will improve large-scale application of anammox processes in mainstream wastewater treatment.展开更多
One-stage partial nitrification coupled with anammox(PN/A)technology effectively reduces the energy consumption of a biological nitrogen removal system.Inhibiting nitrite-oxidizing bacteria(NOB)is essential for this t...One-stage partial nitrification coupled with anammox(PN/A)technology effectively reduces the energy consumption of a biological nitrogen removal system.Inhibiting nitrite-oxidizing bacteria(NOB)is essential for this technology to maintain efficient nitrogen removal performance.Initial ammonium concentration(IAC)affects the degree of inhibited NOB.In this study,the effect of the IAC on a PN/A biofilm was investigated in a moving bed biofilm reactor.The results showed that nitrogen removal efficiency decreased from 82.49%±1.90%to 64.57%±3.96%after the IAC was reduced from 60 to 20 mg N/L,while the nitrate production ratio increased from 13.87%±0.90%to 26.50%±3.76%.NOB activity increased to1,133.86 mg N/m^(2)/day after the IAC decreased,approximately 4-fold,indicating that the IAC plays an important inhibitory role in NOB.The rate-limiting step in the mature biofilm of the PN/A system is the nitritation process and is not shifted by the IAC.The analysis of the microbial community structure in the biofilm indicates that the IAC was the dominant factor in changes in community structure.Ca.Brocadia and Ca.Jettenia were the main anammox bacteria,and Nitrosomonas and Nitrospira were the main AOB and NOB,respectively.IAC did not affect the difference in growth between Ca.Brocadia and Ca.Jettenia.Thus,modulating the IAC promoted the PN/A process with efficient nitrogen removal performance at medium to low ammonium concentrations.展开更多
The long-term impact of fulvic acid(FA)on partial nitritation(PN)systemwas initially examined in this study.The obtained results revealed that the FA lower than 50 mg/L had negligible effect on the nitrite accumulatio...The long-term impact of fulvic acid(FA)on partial nitritation(PN)systemwas initially examined in this study.The obtained results revealed that the FA lower than 50 mg/L had negligible effect on the nitrite accumulation rate(NAR nearly 100%)and ammonium removal rate(ARR 56.85%),while FA over 50 mg/L decreased ARR from 56.85%to 0.7%.Sludge characteristics analysis found that appropriate FA(<50 mg/L)exposure promoted the settling performance and granulation of PN sludge by removing Bacteroidetes and accumulating Chloroflexi.The analysis of metagenomics suggested that the presence of limited FA(0-50 mg/L)stimulated the generation of NADH,which favors the denitrification and nitrite reduction.The negative impact of FA on the PN system could be divided into two stages.Initially,limited FA(50-120 mg/L)was decomposed by Anaerolineae to stimulate the growth and propagation of heterotrophic bacteria(Thauera).Increasing heterotrophs competed with AOB(Nitrosomonas)for dissolved oxygen,causing AOB to be eliminated and ARR to declined.Subsequently,when FA dosage was over 120 mg/L,Anaerolineae were inhibited and heterotrophic bacteria reduced,resulting in the abundance of AOB recovered.Nevertheless,the ammonium transformation pathway was suppressed because genes amoABC and hao were obviously reduced,leading to the deterioration of reactor performance.Overall,these results provide theoretical guidance for the practical application of PN for the treatment of FA-containing sewage.展开更多
基金financially supported by the Natural Science Foundation of Shandong Province, China (No. ZR2019BEE070)a Project of Shandong Province Higher Educational Science and Technology Program (No. J18KA207)。
文摘Residual ammonium is a critical parameter affecting the stability of mainstream partial nitritation/anammox(PN/A), but the underlying mechanism remains unclear. In this study,mainstream PN/A was established and operated with progressively decreasing residual ammonium. PN/A deteriorated as the residual ammonium decreased to below 5 mg/L, and this was paralleled by a significant loss in anammox activity in situ and an increasing nitrite oxidation rate. Further analysis revealed that the low-ammonium condition directly decreased anammox activity in situ via two distinct mechanisms. First, anammox bacteria were located in the inner layer of the granular sludge, and thus were disadvantageous when competing for ammonium with ammonium-oxidizing bacteria(AOB) in the outer layer. Second, the complete ammonia oxidizer(comammox) was enriched at low residual ammonium concentrations because of its high ammonium affinity. Both AOB and comammox presented kinetic advantages over anammox bacteria. At high residual ammonium concentrations,nitrite-oxidizing bacteria(NOB) were effectively suppressed, even when their maximum activity was high due to competition for nitrite with anammox bacteria. At low residual ammonium concentrations, the decrease in anammox activity in situ led to an increase in nitrite availability for nitrite oxidation, facilitating the activation of NOB despite the dissolved oxygen limitation(0.15–0.35 mg/L) for NOB persisting throughout the operation. Therefore, the deterioration of mainstream PN/A at low residual ammonium was primarily triggered by a decline in anammox activity in situ. This study provides novel insights into the optimized design of mainstream PN/As in engineering applications.
基金Project supported by the National Natural Science Foundation of China (No. 50238050)the Hi-Tech Research and Development Program (863) of China (No. 2002AA649250).
文摘Anaerobic ammonium oxidation （ANAMMOX） technology has potential technical superiority and economical efficiency for the nitrogen removal from landfill leachate, which contains high-strength ammonium nitrogen （NH4^＋-N） and refractory organics. To complete the ANAMMOX process, a preceding partial nitritation step to produce the appropriate ratio of nitrite/ammonium is a key stage. The objective of this study was to determine the optimal conditions to acquire constant partial nitritation for landfill leachate treatment, and a bench scale fixed bed bio-film reactor was used in this study to investigate the effects of the running factors on the partial nitritation. The results showed that both the dissolved oxygen （DO） concentration and the ammonium volumetric loading rate （Nv） had effects on the partial nitritation. In the controlling conditions with a temperature of 30±1℃, Nv of 0.2-1.0 kg NH4＋-N/（m^3·d）, and DO concentration of 0.8-2.3 mg/L, the steady partial nitritation was achieved as follows： more than 94% partial nitritation efficiency （nitrite as the main product）, 60%-74% NH4^＋-N removal efficiency, and NO2^--N/NH4^＋-N ratio （concentration ratio） of 1.0-1.4 in the effluent.The impact of temperature was related to Nv at certain DO concentration, and the temperature range of 25-30℃ was suitable for treating high strength ammonium leachate. Ammonium-oxidizing bacteria （AOB） could be acclimated to higher FA （free ammonium） in the range of 122-224 mg/L. According to the denaturing gradient gel electrophoresis analysis result of the bio-film in the reactor, there were 25 kinds of 16S rRNA gene fragments, which indicated that abundant microbial communities existed in the bio-film, although high concentrations of ammonium and FA may inhibit the growth of the nitrite-oxidizing bacteria （NOB） and other microorganisms in the reactor.
基金supported by the Key Research and Development Project of Shandong (Nos.2021CXGC011202,2020CXGC011404,and 2022CXGC021002)the National Natural Science Foundation of China (No.22276006)。
文摘This study employed multispectral techniques to evaluate fulvic acid(FA)compositional characteristic and elucidate its biodegradation mechanisms during partial nitritation(PN)process.Results showed that FA removal efficiency(FRE)decreased from 90.22 to 23.11%when FA concentrations in the reactor were increased from 0 to 162.30 mg/L,and that molecular size,degree of aromatization and humification of the effluent FA macromolecules all increased after treatment.Microbial population analysis indicated that the proliferation of the Comamonas,OLB12 and Thauera exhibit high FA utilization capacity in lower concentrations(<50.59 mg/L),promoting the degradation and removal of macromolecular FA.In addition,the sustained increase in external FA may decrease the abundance of above functional microorganisms,resulting in a rapid drop in FRE.Furthermore,from the genetic perspective,the elevated FA levels restricted carbohydrate(ko00620,ko00010 and ko00020)and nitrogen(HAO,AMO,NIR and NOR)metabolism-related pathways,thereby impeding FA removal and total nitrogen loss associated with N_(2)O emissions.
基金supported by the National Natural Science Foundation of China (No.22176007),the Beijing Natural Science Foundation (No.8212022)the fund of innovation and entrepreneurship leading team project in Guangzhou (No.CYLJTD-201607)the National Key Research and Development Program of China (No.2021YFC3200605)。
文摘Anammox is widely considered as the most cost-effective and sustainable process for nitrogen removal.However,how to achieve the enrichment of anammox biomass remains a challenge for its large-scale application,especially in mainstream wastewater treatment.In this study,the feasibility of enrichment of anammox biomass was explored through the realization of partial denitrification and the addition of bio-carriers.By using ordinary activated sludge,a sequencing batch reactor(SBR)followed by an up-fow anaerobic sludge bed(UASB)was operated at 25±2℃ for 214 days.The long-term operation was divided into five phases,in which SBR and UASB were started-up in Phases I and II,respectively.By eliminating oxygen and adjusting the infow ratios in Phases III-V,advanced nitrogen removal was achieved with the effuent total nitrogen being 4.7 mg/L and the nitrogen removal efficiency being 90.5%in Phase V.Both in-situ and ex-situ activity tests demonstrated the occurrence of partial denitrification and anammox.Moreover,16S rRNA high-throughput sequencing analysis revealed that Candidatus Brocadia was enriched from below the detection limit to in biofilms(0.4%in SBR,2.2%in UASB)and the foc sludge(0.2%in SBR,1.3%in UASB),while Thauera was mainly detected in the foc sludge(8.1%in SBR,8.8%in UASB),which might play a key role in partial denitrification.Overall,this study provides a novel strategy to enrich anammox biomass driven by rapid achievement of partial denitrification through the addition of bio-carriers,which will improve large-scale application of anammox processes in mainstream wastewater treatment.
文摘研究了在低基质质量浓度条件下ANAMMOX生物滤池的脱氮效果.试验结果显示,NH_4^+-N的质量浓度在10～25 mg/L时,厌氧氨氧化滤池具有很高的基质去除率,NH_4^+-N的平均去除率为93.07%,NO_2^--N的平均去除率为82.23%,NO_2^--N与NH_4^+-N适宜的配比值为1.34,生物滤池脱氮高效段的滤池深度为0～60 cm.
基金supported by the National Natural Science Foundation of China(Nos.52070153,52200175)the Key Research and Development Program of Shaanxi,China(No.2023-YBSF-283)。
文摘One-stage partial nitrification coupled with anammox(PN/A)technology effectively reduces the energy consumption of a biological nitrogen removal system.Inhibiting nitrite-oxidizing bacteria(NOB)is essential for this technology to maintain efficient nitrogen removal performance.Initial ammonium concentration(IAC)affects the degree of inhibited NOB.In this study,the effect of the IAC on a PN/A biofilm was investigated in a moving bed biofilm reactor.The results showed that nitrogen removal efficiency decreased from 82.49%±1.90%to 64.57%±3.96%after the IAC was reduced from 60 to 20 mg N/L,while the nitrate production ratio increased from 13.87%±0.90%to 26.50%±3.76%.NOB activity increased to1,133.86 mg N/m^(2)/day after the IAC decreased,approximately 4-fold,indicating that the IAC plays an important inhibitory role in NOB.The rate-limiting step in the mature biofilm of the PN/A system is the nitritation process and is not shifted by the IAC.The analysis of the microbial community structure in the biofilm indicates that the IAC was the dominant factor in changes in community structure.Ca.Brocadia and Ca.Jettenia were the main anammox bacteria,and Nitrosomonas and Nitrospira were the main AOB and NOB,respectively.IAC did not affect the difference in growth between Ca.Brocadia and Ca.Jettenia.Thus,modulating the IAC promoted the PN/A process with efficient nitrogen removal performance at medium to low ammonium concentrations.
基金supported by the Key Research&Developmental Program of Shandong Province(Nos.2021CXGC011202,2020CXGC011404)the Beijing Natural Science Foundation(No.8192004)the Beijing Major Science and Technology Projects(No.Z181100005318001)
文摘The long-term impact of fulvic acid(FA)on partial nitritation(PN)systemwas initially examined in this study.The obtained results revealed that the FA lower than 50 mg/L had negligible effect on the nitrite accumulation rate(NAR nearly 100%)and ammonium removal rate(ARR 56.85%),while FA over 50 mg/L decreased ARR from 56.85%to 0.7%.Sludge characteristics analysis found that appropriate FA(<50 mg/L)exposure promoted the settling performance and granulation of PN sludge by removing Bacteroidetes and accumulating Chloroflexi.The analysis of metagenomics suggested that the presence of limited FA(0-50 mg/L)stimulated the generation of NADH,which favors the denitrification and nitrite reduction.The negative impact of FA on the PN system could be divided into two stages.Initially,limited FA(50-120 mg/L)was decomposed by Anaerolineae to stimulate the growth and propagation of heterotrophic bacteria(Thauera).Increasing heterotrophs competed with AOB(Nitrosomonas)for dissolved oxygen,causing AOB to be eliminated and ARR to declined.Subsequently,when FA dosage was over 120 mg/L,Anaerolineae were inhibited and heterotrophic bacteria reduced,resulting in the abundance of AOB recovered.Nevertheless,the ammonium transformation pathway was suppressed because genes amoABC and hao were obviously reduced,leading to the deterioration of reactor performance.Overall,these results provide theoretical guidance for the practical application of PN for the treatment of FA-containing sewage.
