Effect of return activated sludge diversion ratio on phosphorus removal performance in side-stream enhanced biological phosphorus removal (S2EBPR) process

• Published in: Environmental research 2023-10, Vol.235, p.116546, Article 116546
• Main Authors: Lv, Taotao, Wang, Dongqi, Hui, Jiayao, Cheng, Wen, Ai, Hao, Qin, Lu, Huang, Mengbo, Feng, Minquan, Wu, Yufan
• Format: Article
• Language: English
• Subjects: EBPR; Glycolysis pathway; PAO; Phosphorus removal performance; RAS diversion ratio; Side-stream
• ISSN: 0013-9351; 1096-0953; 1096-0953
• DOI: 10.1016/j.envres.2023.116546

In this study, a lab-scale continuous flow side-stream enhanced biological phosphorus (P) removal (S2EBPR) reactor was operated for 247 days treating synthetic wastewater with influent carbon to phosphorus (C/P) ratio of 25.0 g COD/g P and influent PO43–-P of 7.4 ± 0.3 mg P/L. The effect of the return activated sludge (RAS) diversion ratio on S2EBPR reactor was investigated by comparing P removal performance, microbial activity, and community structure. The results showed that the RAS diversion ratio of 8.0%, by yielding a side-stream sludge retention time (SRTSS) of ∼60 h, resulted in the lowest effluent PO43–-P concentration of 0.5 ± 0.3 mg P/L. The results of in situ process profiles and ex situ P release and uptake batch tests under different RAS diversion conditions showed that the more anaerobic P release was obtained in the side-stream reactor, the higher the P removal efficiency and EBPR activity were achieved. The stoichiometric ratios observed in EBPR activity tests indicated a polyphosphate accumulating organisms (PAOs) metabolism mainly dependent on the glycolysis pathway. The results of microbial ecology analysis revealed that the optimized SRTSS would give a competitive advantage to PAOs in the S2EBPR process. By obtaining statistically reliable results, this study would provide guidance for wastewater treatment plants to achieve optimal P removal performance in S2EBPR configuration. •A 3 L/h continuous flow S2EBPR reactor was started up and operated for 247 days.•The optimum sludge residence time was about 60 h in the side-stream reactor.•A good P removal efficiency can be achieved by adjusting side-stream ratio only.•The PAO/GAO value was well used to evaluate EBPR activity.