COD Requirement for Biological Phosphorus Removal Granule System Under Different Phosphorus Concentrations

Abstract

In this study, the effect of COD loading on a biological phosphorus removal granule system under different phosphorus concentrations was investigated by changing the concentration of total phosphorus (TP) and COD in the influent. The lowest concentration of COD for good performance of the biological phosphorus removal system under different phosphorus concentrations was obtained. The results show that when the concentration of TP was 10 mg·L-1 in the influent, the lowest concentration of COD for good performance of the biological phosphorus removal system was 175 mg·L-1. The concentration of TP in the effluent was below 0.5 mg·L-1; the particle size and SVI were 1020 μm and 36 mL·g-1, respectively; and the contents of PN and PS (by MLSS) were 78 mg·g-1 and 39 mg·g-1, respectively. Furthermore, the PN/PS was lower and the granules had good structure and performance. When the concentration of TP was 6 mg·L-1 in the influent, the lowest concentration of COD for good performance of the biological phosphorus removal system was 150 mg·L-1. The concentration of TP in the effluent was below 0.3 mg·L-1; the particle size and SVI were respectively 960 μm and 35 mL·g-1; and the contents of PN and PS were 75 mg·g-1 and 35 mg·g-1, respectively. Moreover, the PN/PS was lower and the granules had good structure and performance. The removal efficiency of COD was above 83% and the concentration of COD in the effluent was below 25 mg·L-1 throughout the operational process. Under different the influent phosphorus concentrations, the contents of PN and PS decreased, PN/PS increased, particle size decreased, SVI increased, and the structure and performance of the biological phosphorus removal granules deteriorated as the COD concentration decreased.