Development of a double-layer EPS-ASM2d model to illustrate the effect on mainstream biological phosphorus system in side-stream phosphorus recovery process.

Abstract

In order to deeply investigate the influences of side-stream phosphorus (P) recovery operation on mainstream biological P removal system, an improved activated sludge model no. 2 (ASM2d) was established to illuminate the metabolic processes of P in a side-stream P recovery reactor. The improved ASM2d (named D-EPS-ASM2d) was established by extending of the P metabolic processes of double-layer extracellular polymeric substances (EPS) into conventional ASM2d model. The predicted effluent concentrations of COD, NH4, and TP by the D-EPS-ASM2d had good fits with measured values in the side-stream P recovery process. Comparing with conventional ASM2d, the likelihood values of D-EPS-ASM2d related to COD, NH4, and TP effluents were increased from 0.694, 0.837 and 0.762 to 0.868, 0.904 and 0.920, respectively, implying the simulation performances of D-EPS-ASM2d on nutrient removal processes were significantly improved. Besides, the calibrated values of fPP,TEPS was 0.09, 0.102 and 0.123 as side-stream volume (SSV) increasing from 0.3 to 0.9, implying the fraction of P removal by tightly-bound EPS was enhanced with the increase of SSV.