Performance,microbial community and inhibition kinetics of long-term Cu2+ stress on an air-lift nitritation reactor with self-recirculation

Biological nitrogen removal process could be affected due to the presence of heavy metals owing to their toxicity and accumulation in the sludge.In this study,the impact of Cu2+shock on a long-term nitritation operation was investigated in an air-lift reactor with selfrecirculation.Both the dynamics of microbial community and inhibition kinetics under Cu2+stress were ascertained.The results showed that Cu2+exerted severe inhibition on nitritation performance of an air-lift reactor(ALR)at 25 mg/L.The corresponding NH4+-N removal efficiency decreased to below 50%,which was mainly due to the variation of microbial community structure,especially the inhibition of nitrifiers like Nitrosomonas(the relative abundance decreased from 30%to 1%after Cu2+inhibition).Kinetic parameters were obtained and compared after fitting the Haldane model.The long-term Cu2+stress on the ALR aggravated the ammonium affinity and the resistance to substrate self-inhibition of the nitritation sludge,but reduced the resistance to Cu2+inhibition.Furthermore,Cu2+acted as uncompetitive inhibitor on nitritation process.Our results provide new insights into the nitritation characteristics under long-term Cu2+stress.