Application of Subsurface Flow Constructed Wetland System for Purification of Secondary Effluent from Municipal Wastewater Treatment Plant

Abstract

The main objective of this study was to investigate the efficacy of using the constructed wetland for purification of secondary effluent from a wastewater treatment plant (WWTP) in the eastern district of Anyang, Henan province, China. A Subsurface Flow Constructed Wetland (SSFCW) system was designed and constructed, consisting of 302 SSFCW units (L×W×H = 30×20×1.4 m for each unit) with a treatment capacity of 105 m3/d. Each unit of the system was planted with equal number of Phragmites australis, Typha orientalis Presl, and Zizania latifolia at the density of 16 plants/m2 . The average values of the Chemical Oxygen Demand (CODCr), Biochemical Oxygen Demand (BOD5), Ammonia Nitrogen (NH3-N), and Total Phosphorus (TP) of the effluent sampled from 4 outlets of the system chosen at random for 17 months consistently met the Class III of Environmental quality standard for surface water in China, even during the cold season. According to the economic analysis, the system may generate an annual profit of around ¥ 1.4 million yuan. The SSFCW system is an cost-effective and profitable technique for the further polish of the secondary effluent from the wastewater treatment plant.