Factors affecting the performance of horizontal flow constructed treatment wetland vegetated with Cyperus papyrus for municipal wastewater treatment.

The effect of hydraulic loading rate (HLR) and hydraulic retention time (HRT) on the bioremediation of municipal wastewater using a pilot scale subsurface horizontal flow constructed treatment wetland (HFCTW) vegetated with Cyprus papyrus was investigated. Different HLRs were applied to the treatment system namely 0.18, 0.10, and 0.07 m(3)/m(2). d with corresponding HRTs of 1.8, 3.2, and 4.7 days, respectively. The flow rate was 8 m(3)/d, and the average organic loading rate (OLR) was 0.037 kg BOD/m(3)/d. Results showed that the performance of the HFCTW was linearly affected by decreasing the HLR and increasing the HRT. The highest treatment efficiency was achieved at HRT (4.7 days) and HLR (0.07 m(3)/m(2). d). The percentage reductions of chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total suspended solids (TSS) were 86%, 87%, and 80%, respectively. Satisfactory nutrient removal was obtained. Also, removal of 2-3 logs of bacterial indicators of pollution was achieved. The dry biomass of Cyperus was 7.7 kg/m(2) and proved to be very efficient in nitrification processes due to high diversity of the roots that increase the treatment surface area.