Study On The Treatment Effect Of Riverside Filter Belt On Farmland Non-point Source Pollution

Agricultural non-point source pollution is one of main causes of river pollution in China,and it needs to be controlled to ensure the safety of river water quality.The riparian zone can effectively block non-point source pollutants from entering the river.Therefore,this paper designs a riverside filter belt,and studies the adsorption kinetics of packing of filter belt on Chemical oxygen demand(COD),total nitrogen(TN),total phosphorus(TP),ammonia nitrogen(NH4+-N)and nitrate nitrogen(NO3--N).Through the simulation experiment,the removal effect of the filter belt on the pollutants in simulated runoff is studied.Then,according to the actual situation of the riparian zone in the upstream of the Miyun Reservoir,a design project for the demonstration project of non-point source pollution control in the riparian zone was proposed.This paper studied the adsorption kinetics of three kinds of fillers in filter belt,and the result showed that the adsorption of COD and ammonia nitrogen by anthracite,ceramsite and zeolite was mainly affected by diffusion.Anthracite has the best adsorption effect on TP,and its adsorption capacity is 0.065 mg/g;Zeolite has the best adsorption capacity for ammonia nitrogen and TN,with 0.095and 0.106 mg/g,respectively;ceramsite has the best adsorption effect on COD,and its adsorption capacity is 0.871 mg/g.This paper studied the purification effect of filter belt on non-point source pollutants in farmland.The results showed that the flow has a certain effect on the removal effect.The reduction rate of nitrate nitrogen and TN is the highest under high flow rate,the reduction rate of COD and ammonia nitrogen is the highest under medium flow rate,the reduction rate of TP is the highest under small flow rate.When the influent concentration is high,the filter belt has a better effect on reducing COD,TP,nitrate nitrogen and TN,and the effect of reducing ammonia nitrogen is better when the concentration is low.The filler ratio also affects the reduction rate of pollutants by the filter belt,when the ratio of anthracite,ceramsite and zeolite is 3:5:2,the filter belt has the highest reduction rate of TP,ammonia nitrogen and TN.When the ratio of anthracite,ceramsite and zeolite is 5:12:3,the filter belt has the highest reduction rate of COD and nitrate nitrogen.The concentration reduction rates of COD,TP,ammonia nitrogen,nitrate nitrogen and TN by the filter belt are 26%?28%,82%?95%,72%?90%,2%?12%and 25%?38%respectively under different packing ratios.According to the actual situation of the river's riparian zone in the upstream of Miyun Reservoir,based on the analysis of the basic conditions and water quality restoration targets of Xikouwai small watershed at the demonstration area,this paper designed a demonstration project for the riverside filter belt in Xikouwai small watershed.A total of nine first-level filter belts were designed,with a total length of 3000 meters,and two three-level filter belts were designed,with a total length of 400 meters.The blocking effect of filter belt on non-point source pollution of farmland and runoff pollution can provide guarantee for the safety of river water quality.