Effect of different enrichment methods on the independent biological phosphorus removal performance after nitrogen removal using immobilized fillers

Abstract

In order to find a biological phosphorus removal enrichment method with high performance and low energy consumption, two enrichment methods were used in this study, namely gradient carbon source addition (S1) and fixed carbon source addition (S2). The two enrichment methods were applied to the enrichment of phosphorus removing bacteria in an independent biological phosphorus removal system based on nitrogen removal by immobilized fillers. The phosphorus removal performance, stoichiometry and microbial structure were compared for the two enrichment methods. It was found that PO43--P remained 0.15–0.2 mg/L at the end of enrichment in S1, while PO43--P increased from 0.27 to 0.38 mg/L at the end of enrichment in S2. Stoichiometric analysis showed that S1 used more PHAs (1.47 molC/L) for phosphorus absorption, while S2 used nearly half of the PHAs (0.87 molC/L) for glycogen synthesis. Moreover, the absorbed phosphorus content in S2 was significantly less than S1 (5.67 < 8.65 mg/L). As a result, denitrifying phosphorus-removing bacteria predominated S1, while phosphate-accumulating organisms (PAOs) and glycogen-accumulating organisms (GAOs) both played a role in S2. Dechloromonas, the dominant denitrifying PAO in both S1 and S2 increased from 0.26 % to 3.34 % and 1.04 %, respectively, while Defluviicoccus, a typical GAO, changed from 0.24 % to 0.2 % and 2.01 %, respectively. As a result, gradient carbon source enrichment demonstrated a better phosphorus removal effect and dominant bacteria, whereas the fixed carbon source enrichment increased the abundance of GAOs while negatively impacting the phosphorus removal effect.