[Biological nitrogen and phosphorus removal in the anaerobic-aerobic-anoxic-aerobic-anoxic-aerobic sequencing batch reactors].

The biological nitrogen and phosphorus removal was investigated in two anaerobic-anoxic-aerobic sequencing batch reactors (SBRs), which were fed with synthetic and municipal wastewater, respectively. The operating cycle of (AO)3 SBR was 1.5 h anaerobic --> 1 h aerobic --> 1 h anoxic -->20 min aerobic --> l h anoxic --> 20 min aerobic. The removal efficiency of COD, total nitrogen and total phosphorus for synthetic wastewater was 88%, 89%, 99%, respectively, while it was 85%, 75% , 99.5% for municipal wastewater. Furthermore, it was observed that though there were much differences in polyhydroxyalkanoates (PHAs) accumulation and phosphorous release in the anaerobic stage between two SBRs, the ratio of the anoxic energy production efficiency to the aerobic one was close to each other (49% versus 50%).