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).

with the A2/O process,a pilot test system for enhancing biological nitrogen and phosphorus removal by using the A2/O-membrane bioreactor(A2/O-MBR)was constructed and used to treat municipal wastewater.

Tests on biological nitrogen and phosphorus removal by a spiral up-flow reactor (SUFR) system were described in this paper.

The current research results and progress on the mechanism of biological nitrogen and phosphorus removal from municipal sewage from home and abroad were reviewed.

General situation studying on new technology of biological nutrient removal is summarized,such as the principle of denitrifying dephosphataion and factors affecting it,such as pH,DO,SRT,MLSS etc.

It is a focal problem in conventional biological nutrient removal that denitrifying bacteria compete with phosphate accumulating organisms(PAO) for limited dissolved organisms.

This thesis examined the feasibility of using fermentative Short-chain Fatty Acids (SCFA, which was produced from waste activated sludge affected by surfactant) as the carbon sources of biological nutrient removal (BNR) system, Which has been focused in the research of the metabolic mechanism of nitrogen, phosphorus, SCFA, polyhydroxyalkanoates (PHAs), glycogen et al.

This paper introduces the principles of biological phosphorus and nitrogen removal with the A2/O process and decribes the flow chart of this process which is then analyzed in detail.

It was suggested that for the biological phosphorus and nitrogen removal system without primary clarifier, net process yield Y_n or total yield coefficient Y_(BOD) should be used, which was capa.