Removal of nutrient and bacteria in pilot-scale constructed wetlands

Abstract

Three pilot-scale horizontal-subsurface flow (H-SSF), surface flow (SF), and free water surface flow (FWS) constructed wetland system designs were installed and evaluated to determine the effectiveness of constructed wetlands to treat tertiary effluent wastewater generated from Paşaköy Advanced Biological Wastewater Treatment Plant (PABWWTP). The average ammonia-nitrogen (NH+ 4) removal efficiencies of % 49 to 52% were observed in all three system designs. Average NO− 3 removal efficiency was approximately 58% in the SF system design, suggesting that this design had the highest denitrification rate. Total phosphorus (TP) removal efficiency was the highest (approximately 60%) in the h-SSF system, possibly due to substrate (gravel). Systems were capable of removing approximately 94% of fecal coliform (FC) bacteria. Removal rate coefficients (k 20, 1/day) in the H-SSF, the FWS and the SF systems were estimated for NH+ 4, NO− 3, TP and FC. The average nutrient removal efficiencies were found higher in the summer periods except for the FC. The results of statistical analyses indicated that nutrient removals were affected by temperature, hydraulic residence time (HRT), and nitrogen loading rate (NLR).