Contaminant Removal Efficiency from Domestic Wastewater Using Experimental Constructed Wetlands Planted with Cyperus ligularis (Cyperaceae) and Echinochloa colonum (Poaceae)

This study evaluated the removal efficiency of organic matter (COD), nitrogen (NH4+, NO3-) orthophosphate and total and fecal coliforms in four horizontal subsurface flow pilot scale constructed wetlands using two species of local plants. Two systems were planted with Cyperus ligularis and two Echinochloa colonum. The experiment consisted of sedimentation tank of 760 L (primary treatment) from where water was poured, through PVC pipe to constructed wetlands system. Each wetland was filled with gravel of a diameter of 8 mm and porosity of 0.4. Once a day during four months, wetlands added a flow rate of 42 l.day(-1) to maintain a hydraulic residence time of three days. Wastewater samples (influent and effluent) were collected three times by week for COD and nutrients concentrations. Once a week the fecal and total coliforms were analyzed. Removal efficiency of COD, ammonium, nitrate and orthophosphate were of 93, 65, 71 and 32%, respectively for C. ligularis and of 85, 54, 67 and 57%, respectively for E. colonum. Removal efficiency of total and fecal coliforms was on 99.9% for both species. The results indicated no significant difference (P < 0.05) in the removal of principals contaminants in the wetland planted C. ligularis indicating higher ability of this species for the treatment of domestic wastewater.