Sequential Hybrid Constructed Wetland For Effective Nutrient Removal From Municipal Wastewater Treatment Plant Effluent: A Full Scale Case Study

Tangxi River receives effluents from several wastewater treatment plants (WWTPs), which need additional treatment to meet the more stringent standards for discharge into this river. A field-scale sequential hybrid constructed wetland (SHCW) system comprising of ecological floating beds with biofilms, zeolite filter beds, facultative pond, and an ecological pond with submerged plants was built for the improvement of the effluent quality. SHCW exhibited significant removal efficiency of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and total phosphorus (TP) with average monthly removal efficiency of 72.52% +/- 3.89%, 91.58% +/- 3.12%, and 76.29% +/- 8.15%, respectively, during the survey period. After treatment, the final concentration of COD, NH4+-N, total nitrogen (TN), and TP in the effluent was 13.75 +/- 0.51, 0.39 +/- 0.03, 11.89 +/- 0.51, and 0.09 +/- 0.05 mg/L, respectively. Moreover, the treatment units showed seasonal variations in COD, NH4+-N, TN, and TP removal efficiency, and summer was the best season for pollutant removal. The treatment cost of SHCW was estimated to be 0.29 RMB/m(3) ($0.044/m(3)), which makes it a cost-effective, feasible, and favorable environmental treatment method for the improvement of treated wastewater. Therefore, WWTPs are recommended to be accompanied with SHCW to achieve acceptable effluent quality and provide a better environment.