Biological Phosphorus Removal Characteristics in a Full-scale Unitank Wastewater Treatment Plant

The biological phosphorus (P) removal characteristics of a full-scale Unitank wastewater treatment plant (WWTP) were investigated by field survey, model analysis and sludge P content determination. In the Unitank WWTP, oxidation-reduction potential (ORP) reached the lowest value of -17 mV and the highest value of 130 mV at the end of anoxic/anaerobic stage and aerobic stage, respectively. The anaerobic P release process could be fitted by first-order kinetics with rate constant of 3.52 h(-1), while the maximum aerobic P uptake rate was 3.31 mgP/(L.h). The measured sludge P content in the Shidongkou WWTP was 15.4 +/- 2.1 mgP/gSS, significantly lower than that in full-scale AAO WWTPs.