Removal of Multiple Contaminants from Agricultural Water Using Versatile Filtration

Abstract

Agricultural runoff contains a mixture of particulate and dissolved contaminants that are difficult to remove simultaneously using conventional filtration media. Here, we developed multifunctional reactive filter media by functionalizing sand with Fe-, Al-, and Mg-based phases, with Mg recovered from mine tailings through acid dissolution. Seven modified media were compared with unmodified sand using real agricultural runoff in column filtration experiments. The modified media consistently outperformed unmodified sand. Phosphorus removal reached 99%, producing effluent concentrations below 0.5 mg P L⁻¹, whereas total organic carbon and turbidity removals reached 89% and 95%, respectively. The media also retained dissolved metals. Among the tested materials, the S-Mg-Al-Fe medium achieved the highest overall performance, with an initial nitrate removal of approximately 74% and >99% glyphosate removal. Repeated filtration experiments showed sustained treatment performance over 20 filtration cycles, whereas pH-dependent tests and surface characterization revealed a chemically heterogeneous interface, suggesting the contribution of complementary contaminant-retention mechanisms. These findings demonstrate that multicomponent surface functionalization can transform conventional sand into a multifunctional filtration medium capable of simultaneously removing diverse contaminants from agricultural waters. The study further illustrates how mine-derived materials can be integrated into decentralized treatment technologies, linking water quality improvement with resource recovery.