Partial nitritation(PN)-anaerobic ammonium oxidation(anammox)is a promising pathway for the biological treatment of wastewater.However,the destruction of the system caused by excessive accumulation of nitrate in long-...Partial nitritation(PN)-anaerobic ammonium oxidation(anammox)is a promising pathway for the biological treatment of wastewater.However,the destruction of the system caused by excessive accumulation of nitrate in long-term operation remains a challenge.In this study,PNanammox was initialized with low inoculation quantity in an air-lift reactor.The nitrogen removal rate of 0.71 kgN/(m^(3)·d)was obtained,which was far higher than the seed sludge(0.3 kgN/(m^(3)·d)).Thereafter,excess nitrate build-up was observed under low-loading conditions,and recovery strategies for the PN-anammox system were investigated.Experimental results suggest that increasing the nitrogen loading rate as well as the concentration of free ammonium failed to effectively suppress the nitrite oxidation bacteria(NOB)after the PN-anammox system was disrupted.Afterwards,effluent back-flow was added into the reactor to control the up-flow velocity.As a result,an aggressive discharge of sludge that promoted the synergetic growth of functional bacteria was achieved,leading to the successful restoration of the PN-anammox system.The partial nitritation and anammox activity were in balance,and an increase in nitrogen removal rate up to 1.07 kgN/(m^(3)·d)was obtained with a nitrogen removal efficiency of 82.4%after recovery.Besides,the proportion of granular sludge(over 200 mm)increased from 33.67%to 82.82%.Ammonium oxidation bacteria(AOB)along with anammox bacteria were enriched in the granular sludge during the recovery period,which was crucial for the recovery and stable operation of the PN-anammox system.展开更多
基金supported by the Beijing Science and Technology Plan Project(No.Z181100005518003)the National Natural Science Foundation of China(Grant No.51978007)the National Key Research and Development Plan Project(No.2016YFC0401103)。
文摘Partial nitritation(PN)-anaerobic ammonium oxidation(anammox)is a promising pathway for the biological treatment of wastewater.However,the destruction of the system caused by excessive accumulation of nitrate in long-term operation remains a challenge.In this study,PNanammox was initialized with low inoculation quantity in an air-lift reactor.The nitrogen removal rate of 0.71 kgN/(m^(3)·d)was obtained,which was far higher than the seed sludge(0.3 kgN/(m^(3)·d)).Thereafter,excess nitrate build-up was observed under low-loading conditions,and recovery strategies for the PN-anammox system were investigated.Experimental results suggest that increasing the nitrogen loading rate as well as the concentration of free ammonium failed to effectively suppress the nitrite oxidation bacteria(NOB)after the PN-anammox system was disrupted.Afterwards,effluent back-flow was added into the reactor to control the up-flow velocity.As a result,an aggressive discharge of sludge that promoted the synergetic growth of functional bacteria was achieved,leading to the successful restoration of the PN-anammox system.The partial nitritation and anammox activity were in balance,and an increase in nitrogen removal rate up to 1.07 kgN/(m^(3)·d)was obtained with a nitrogen removal efficiency of 82.4%after recovery.Besides,the proportion of granular sludge(over 200 mm)increased from 33.67%to 82.82%.Ammonium oxidation bacteria(AOB)along with anammox bacteria were enriched in the granular sludge during the recovery period,which was crucial for the recovery and stable operation of the PN-anammox system.
