Abstract:

To explore the treatment model for farmland drainage pollutants, this study conducted an experimental investigation from July to September 2023 on the interception and purification effects of ecological drainage ditches, constructed wetlands, and their combined system in the Hetao Irrigation District. The findings demonstrate that various treatment modes in ecological drainage ditches and constructed wetlands effectively remove nitrogen and phosphorus pollutants. Specifically, the reduction efficiency of total nitrogen (TN) and total phosphorus (TP) in ecological drainage ditches treated with skew stem Astragalus membranaceus, yellow sweet clover, alfalfa, bio-ball matrix, and bio-sheet matrix was 21.09% and 23.84%, 12.06% and 26.67%, 20.08% and 34.15%, 23.65% and 20.56%, and 19.92% and 25.83%, respectively. In the emergent and submerged aquatic plant areas, the reduction efficiency of TN and TP was 24.28% and 17.89%, and 26.85% and 10.21%, respectively. The ecological drainage ditches treated with alfalfa and bio-ball matrix showed superior performance in TP and TN removal, respectively. Similarly, emergent and submerged plant areas exhibited better TP and TN removal efficiencies. The combined system of ecological drainage ditch and constructed wetland achieved TN and TP removal rates of 37.55% and 11.47%, respectively, effectively realizing step-by-step interception, adsorption and purification of pollutants. This system significantly enhances the removal and purification of nitrogen and phosphorus pollutants, thus mitigating agricultural non-point source pollution.

Key words: ecological drainage ditch, constructed wetland, pollutants, purification effect, Hetao Irrigation District