The efficacy of plants and their growing matrix in improving purification of farmland receding water in constructed wetlands

Abstract

【Objective】 Nonpoint source pollution poses a significant threat to the surface water environment, particularly in agricultural systems. Reconstructed wetlands are an environmentally friendly method to mitigate nonpoint source pollution. This paper investigates the efficacy of plants and their growing medium in removing pollutants from farmland receding water. 【Method】 The experiment was conducted in a subsurface-flow wetland and an ecology surface flow wetland at Bapaigan region along the bank of Duliujian River. We measured the impact of aquatic plant species, planting density, matrix materials and filling rate, and hydraulic retention time of water in the wetland on purification of the water. 【Result】 Among all treatments we compared, the combination of plant species of Scirpus tabernaemontani+ Iris tectorum and matrix of zeolite+ volcanic rock was most effective to purify the receding water, as they nurtured a microbial community which increased denitrification and dephosphorization. Keeping the hydraulic retention time 3 day and running 10 consecutive cycles can remove ammonia nitrogen, total phosphorus and chemical oxygen demand (COD) contents by 95.74%, 49.94% and 89.03%, respectively. 【Conclusion】 Following the implementation of the Bapaigan constructed wetland, the plants, substrate medium and their associated microbiome were effective to remove the pollutants from the receding water, with the effluent water quality reaching Class V standard for surface water. These findings have important implications for remediating farmland runoff using constructed wetlands in north China.

Keywords

• plant
• matrix
• farmland receding water
• constructed wetland
• microorganism