Organics and phosphorus removal in circular flow corridor constructed wetland system

In the present study, the performance of a circular flow constructed wetland (CFCW)1 system was assessed for organics and total phosphorus removal from fertilizer plant effluent. The CFCW system has five media compartments containing gravel, slag iron, and a mixture of sand and zeolite as the media substrates. Synthetic fertilizer wastewater having initial COD 520.98 +/- 8.27 mg/L, was fed to the wetland, maintaining hydraulic loading rate of 6.945 L/m2-h. Typha angustifolia was used as the wetland vegetation. The Phase 1 of the study included three cycles, with influent phosphorus concentrations 10, 20, and 30 mg/L, respectively without step feeding and effluent recirculation. The Phase 2 of the study included two cycles with influent phosphorus concentrations of 20 and 30 mg/L, and application of step feeding and effluent recirculation strategies. The average phosphorus removal efficiencies of the system in three cycles of Phase 1 were 85.16 %, 88 %, and 81.95 %, respectively, along with average COD removal of 87.48 %, 87.65 %, and 86.84 %, respectively. The average phosphorus removal efficiencies of the system in two cycles of Phase 2 were 89.01 % and 90.22 % respectively, along with average COD removal of 91.6 % and 91.23 %, respectively. The step feeding and effluent recirculation strategies have shown satisfactory improvement in organics and total phosphorus removal performance of the CFCW system. However, future long-term studies are recommended involving an unplanted control system, step feeding and effluent recirculation in varying compartments, and varying combination of media substrates for improving the design and performance of the CFCW systems.