Improving phosphorus removal by pre-concentration of return sludge in novel oxidation ditch system
耦合回流污泥预浓缩系统的新型氧化沟工艺强化除磷

In order to solve the problem that the traditional "anaerobic zone + oxidation ditch (OD)" process had a low phosphorus removal efficiency on treating low-carbon municipal wastewater, a novel OD integrated return activated sludge (RAS) pre-concentration system was adopted in this pilot-scale study. RAS pre-concentration system was adopted for promoting the phosphorus removal efficiency through varying the RAS pre-concentration ratio in this process. The results showed that under the optimal RAS pre-concentration ratio(55%)operational condition, effluent TP concentration was 0.92 mg/L, and the removal rate of TP was 67.5%, which increased by 24.3%, 27.3%, 8.2% and 28.6% comparing with the different operations in the RAS pre-concentration ratios of 100%, 70%, 50% and 30%, respectively. Obviously, it improved the effect of the phosphorus removal. Otherwise, ORP (oxidation reduction potential) could predict secondary phosphorus release and denitrification react degree in pre-anoxic tank, so it could be the control parameter to regulate the optimal RAS pre-concentration ratio automatically.