The Effectiveness of a Semi-Artificial Wetland in Removing Microbial Indexes and Agricultural Herbicides from Agricultural Drainage Water

Agricultural drainage water is a significant source of return water due to its decentralization, large volume, and poor quality. This study examined the effectiveness of constructed wetlands in improving sugarcane field’s drainage water in the south of Khuzestan province of Iran, located approximately 17 km north of Khorramshahr city at latitude 303,805.94′ N and longitude 480,759.86′ E, by removing agricultural herbicides (atrazine, glyphosate, paraquat, and 2, 4-D) and Total Coliforms (TC) and Fecal Coliforms (FC) from April 2019 to March 2020. A reed length was divided into three equal parts at three consecutive stations, ST1, ST2, and ST3. Natural reeds had a dimension of 3.5 km long, 1.2 km wide, and 0.5 m deep between two consecutive stations. According to the study, natural reeds were effective in removing agricultural herbicides and improving agricultural drainage water quality. ST3, which was the furthest from the entry point, had the largest difference in agricultural herbicides concentrations compared to their initial concentrations, as well as the highest removal efficiency (100%) during all four retention times (1.26, 1.10, 1.30, and 1.60 days). Natural reed at this distance from the entry point significantly reduced TC and FC. The ST3 station had the highest removal efficiency of TC and FC, with average values of 62 and 83%, respectively, while ST1 had the lowest (with values of 9 and 34%). Due to the differences in performance between ST1, ST2 and ST3 stations, ST2 is considered the most efficient and cost-effective station. The Khuzestan province has a water shortage and agricultural drainage water problems. Treating drainage water with environmentally friendly methods, like natural reeds, will prevent contamination of water sources and result in a significant amount of water entering the system.