Abstract:The activated sludge and bio-membrane system was used to enrich denitrifying phosphorus bacteria (DPB) for removing nitrogen and phosphorus simultaneously. A DPB strain was screened after enrichment and denitrifying phosphorus accumulating experiments were investigated. The change of HAC/phosphate/nitrate/PHB and glycogen were studied in order to analyze the anaerobic and anoxic metabolism and the function of PHB during the process. Strain YB was similar to Paracoccus denitrificans. It was a kind of non-fermentive DPB. Strain YB released 0.11mg P per 1mg PHB during anaerobic stage. As a kind of non-fermentive bacteria, the energy was mostly from the release of poly-phosphate. Strain YB accumulated 0.15 mg P per 1mg PHB during anoxic stage. ATP from the breakdown of PHB was mostly used to accumulate phosphate. The metabolism was different from that of reported phosphate accumulating organisms (PAO). The release of poly-phosphate affected the synthesis of PHB and the impact of denitrifying and accumulating phosphate. It was very important to monitor △P/△PHB and △NO3--N /△PHB, not △P/△COD、△NO3--N /△COD or △P/△NO3--N.