Abstract: Industrial and agricultural wastes have a promising application in the removal of pollutants from livestock farming wastewater. In this study, three industrial and agricultural wastes, including magnesium slag, iron slag, and biochar, were selected to mix in a volume ratio of 1∶1∶1. The composite materials were then mixed with surface soil with the volume ratios of 0.75%, 2%, 5% and 10% to conduct soil column transport experiments under steady-state saturation conditions. The results showed that the removal rate of pollutants from swine wastewater was positively correlated with the amount of mixed material, with the highest removal rate in the columns filling with 5%-10% mixed material. The removal rate of total nitrogen (TN) was 29.89% and the cumulative removal amount was 21.95 mg·kg^-1. The removal rate of total phosphorus (TP) was 57.49% and the cumulative removal amount was 15.03 mg·kg^-1. The removal rate of chemical oxygen demand (COD) was 18.08% and the cumulative removal amount was 363.11 mg·kg^-1. The removal rate of biochemical oxygen demand (BOD₅) was 38.52% and the cumulative removal amount was 6.59 mg·kg^-1. The removal rate of turbidity reached 19.22% and the cumulative removal amount was 210.78 NTU. Our results demonstrated that soil mixing with 5%-10% of composite materials can effectively remove more than 20% of pollutants from wastewater. Our results can provide scientific basis for the interception and deterrence strategy of surface pollution mainly from livestock farming wastewater.

Key words: industrial and agricultural wastes, livestock farming wastewater, dynamic transport, soil filtration, COD removal