Furthermore, the influences of operating conditions, such as dissolved oxygen (DO) and solid retention time (SRT) on the reactor\'s removal efficiencies were mainly investigated.

Effect of SRT on Minimization of Excess Activated Sludge Production;

Effect of Carbon Source and SRT on Denitrifying Phosphorus Removal;

The results show that extending sludge retention time(SRT) can improve the capability of anaerobic phosphorous release,while total phosphorous removal rate is not influenced by SRT.

The results indicate that the contribution of anoxic denitrifying phosphorus removal to total phosphorus removal becomes larger with prolonging the sludge retention time.

The difference in denitrifying phosphorus removal performance between biofilm process and activated sludge process was analyzed in aspects of biomass,sludge retention time and mass ratio of carbon,nitrogen and phosphorus.

Based on the concept of sludge retention time(SRT),the difference between general SRT and aerobic SRT is pointed out in this paper and it shows that the SRT of each reaction phase,such as anaerobic,anoxic and aerobic one,are more important than general SRT in biological phosphorus and nitrogen removal system(BPNRS).