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Combined Effect of Matrix Dams and Paddy Field Drainage Ditches on Nitrogen and Phosphorus Removal

Jing Cheng , Hao Yang, Haisheng Liu, Fangli Su, Hiba Shaghaleh, Yu Peng, Yousef Alhaj Hmoud

Abstract

Context. Nitrogen and phosphorus contaminants from paddy field drainage flow into the receiving bodies of water, posing a risk of eutrophication. To mitigate this pollution risk, several technologies, including constructed wetlands, ecological revetments, and ecological floating beds, have been introduced in drainage ditches. However, these technologies’ capacity to intercept pollutants need to reconstruct the existing ditch structure. Aims. This study aimed to optimize the interception and purification capabilities of drainage ditches through matrix dams. Methods. A hydrodynamic and water quality numerical model was established using the Mike 21 software, and the comprehensive ability of purifying pollutants by the interception of matrix dams and drainage ditches was evaluated. Key results. We found that the overall average flow rate was reduced by 84% in the paddy field drainage ditch after introducing matrix dams, and pollutant concentrations decreased progressively from upstream to downstream. Total nitrogen concentrations were reduced by exceeding 60%, with a maximum reduction in total dissolved nitrogen concentrations of 84.3%. Conclusions. Results indicate that the combined deployment of drainage ditches and matrix dams is effective in removing nitrogen and phosphorus pollutants from paddy field drainage. Implications. This study can provide a theoretical foundation for the practical implementation of matrix dams.

MF24274  Accepted 21 August 2025

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