Optimization of phosphorus reduction in BNR process for urban watershed management

The removal of the phosphorus contained in wastewater can be carried out by physic-chemical or by biological phosphorus removal (EBPR) process. Currently, the biological phosphorus removal process has been attracting attention. Because of its low capital and operational costs compared with those of chemical precipitation processes. According to the U. S. Environmental Protection Agency (EPA), TPeff. concentration decrease to 0.3 mg/l by using the biological treatment [1,2]. Therefore, in this study, we experimented with enhancing the BNR process by injecting an external carbon source into the anaerobic phase. Afterwards, when the phosphorus was released or accumulated in poly-p accumulating organisms (PAOs), we measured the behavior of cations. When the BNR process is injected with an external carbon source in the anaerobic phase was operated, the removal efficiency of TP in the effluent was 94.48% at the maximum, and Org-P, which is difficult to remove by chemical treatment only, was removed considerably. Likewise, some of the external carbon source affected the nitrogen removal. By estimating the metal cations concentration in the anaerobic phase, K+, Mg2+ was used as a parameter to control the amount of external carbon which had to be injected. Our results showed that TP treatment with BNR met the criteria of effluent quality and is a cost-effective and environmentally sound alternative when compared with chemical treatment.