Efficiency of denitrifying simultaneous nitrogen and phosphorus removal and side-stream phosphorus recovery process

Generally, it is unsuitable for treatment of domestic wastewater with a low C/N ratio by conventional wastewater treatment processes due to the lack of carbon source in sewage, probably leading to not meeting the A in first-grade sewage effluent discharge standard of GB18918-2002. For this, development of an economic and environmental friendly process for treating of domestic wastewater is urgent, which may provide a benefit for development of wastewater treatment technologies and enhancement of water environmental quality. Moreover, phosphorus is a non-renewable resource and the quantities of mineral phosphorus resources are rapidly decreasing in the world due to increase in demanding of the industrial and agricultural activities. Recovery of phosphorus is regarded as one of effective strategies for preventing exhaustion of phosphorous rock. Domestic wastewater and its treatment processes are commonly a potential source for phosphorus recovery, which may provide a new way for development of sewage treatment process linking nutrients removal with phosphorus recovery. In recent years, theories development in denitrifying simultaneous nitrogen and phosphorus removal and induced crystallization may give a new idea and direction for exploitation of new domestic wastewater treatment process linking nutrients removal with phosphorus recovery. A novel process for nutrients biological and phosphorus recovery from domestic wastewater with a low C/N ratio was proposed in this study. Effectiveness of the new process of denitrifying simultaneous nitrogen and phosphorus removal and side-stream phosphorus recovery was assessed by investigating the chemical oxygen demand (COD), total nitrogen (TN), ammonium nitrogen (NH4+-N) and phosphate (PO43--P) removal performances and phosphorus recovery efficiency. The wastewater with COD, TN, NH4+-N and PO43--P concentrations of 239.2-259.5, 39.6-43.8, 38.2-41.8 and 8.72-11.40 mg/L, respectively, belongs to low C/N sewage. We used those low C/N ration waste water in the influent, and those in the effluent were 15.2-21.6, 8.5-9.6, 3.6-4.7 and 0.31-0.49 mg/L, meeting the A in first-grade sewage effluent discharge standard of GB18918-2002. The COD removal efficiency in anaerobic tank was significantly higher than that in other tanks and NH4+-N removal mainly occurred in the aerobic tank. In the process, phosphorus in the influent was removed mainly by denitrifying phosphate accumulating organisms (DPAO) and induced hydroxyapatite (HAP) crystallization, where the phosphorus total removal efficiency was 95.9% obtained here and 71.5% of that was completed in the induced crystallization (IC) column, suggesting the advantages of the process in the phosphorus recovery. Moreover, the post-aeration tank can remove any surplus carbon, nitrogen and phosphorus, thus contributing to enhance the water quality of effluent. The results obtained from here may serve as a new approach for nutrients removal combined with phosphorus recovery from domestic wastewater. © 2016, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.