| A Carrousel oxidation ditch and a secondary sedimentation tank of sewage treatment equipment had been set up in order to investigate the mechanism of simultaneous nitrogen and phosphorus removal of sewage and characteristics of microbial community in this research system. Characteristics of microbial community structure were analyzed by employing Fluorescence in situ Hybridization. A kinetic model of phosphorus removal has been established and the effect of Al3+ and Fe+on phosphorus removal was investigated. The results show that the TN, TP removal rate are negatively correlated with DO concentration, while positively correlated with TCOD/TN.The TN removal rate is positively correlated with the reflux ratio, with which the TP removal is negatively correlated. The TN removal rate increases with HRT, but TP removal efficiency decreases with HRT. Ammonia oxidizing bacteria, Nitrosomonas spp. and Nitrosospira spp. are punctate distributed in low DO concentration, while denitrifying bacteria is punctate distributed in high DO concentration. The quantity of ammonia oxidizing bacteria, Nitrosomonas spp. and Nitrosospira spp.increase with DO concentration while reduce with C/N ratio, and the influence of SRT is not observed obviously. The quantity of denitrifying bacteria is negatively correlated with DO concentration and C/N ratio, respectively, but increase with SRT. The rate of phosphorus release and uptake decreased respectively with time. The rate of TP removal increases with TCOD/TP, while decreases with the load of phosphorus release and uptake. A kinetic model of phosphorus removal has been established;The maximal TP removal is obtained at Al3+,Fe2+ concentration of 10-30 mg·L-1 and 20 mg·L-1.
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