Ma Development Of New Ecological Interception Ditch And Its Application In Non-point Source Pollution Control

Due to the unreasonable use of chemical fertilizers and pesticides,farmland non-point source pollution has become an important cause of water quality deterioration in China.Ditches are often the source and sink of surface runoff.Ordinary drainage ditches do not have the function of removing pollutants,and even become the source of pollutant flow.Ecological ditches are an important way to solve this problem,but traditional ecological interception ditches have seasonal problems.Therefore,this study changed the farmland drainage ditch into an ecological interception ditch,and set up a plant layer and a filler layer on the original basis.Several materials with good effect of nitrogen and phosphorus removal were selected by filter column experiment,and the most suitable ratio was selected.Ecological ditch simulation experiments were carried out indoors to compare the effects of different ditches on removing pollutants in static and dynamic flow processes,and to evaluate the removal ability of new ecological interception ditches under different hydraulic conditions and different slopes.The field engineering demonstration was carried out,and the new ecological interception ditch was used to treat the aquaculture wastewater,and the actual operation effect of the ditch was monitored.The main results of this study are as follows:（1）In the adsorption experiment,the adsorption effect of the filler was comprehensively investigated.Iron-modified biochar,limestone and zeolite were selected as the main fillers of the ditch.The three fillers were combined and the ratio of the fillers in the ditch was finally determined.The weight ratio was iron-modified biochar:zeolite:limestone=2:2:1.In the filter column adsorption experiment,the removal rate of NH₄⁺-N by the filler under this ratio reached 92.40%,and the removal rate of TP reached 85.60%..（2）By building a simulation device for ecological interception ditches and ordinary soil ditches indoors,the removal effects of the two ditches on pollutants under dynamic and flowing conditions were studied.The results showed that the removal efficiency of NH₄⁺-N,NO₃^--N,total nitrogen（TN）and TP in the new ecological interception ditch was significantly better than that in the ordinary ditch under two different conditions.In addition,the new ecological interception ditches are grouped to explore the influence of different inlet flow rates on the pollution removal capacity of ditches and the pollution control capacity of ditches with different slopes.It is found that the ecological interception ditch still has good decontamination ability under three kinds of inlet flow conditions.In general,the greater the flow,the higher the concentration of effluent pollutants.With the increase of influent time,the indexes of effluent increased to varying degrees,among which the increase of effluent NO₃^--N concentration was the most obvious,but there was also at least66.70%removal rate.The slope also has little effect on the effluent quality of the new ecological interception ditch.With the increase of slope,the removal rate of all indicators except TP decreases.（3）A new ecological interception ditch was built next to the bullfrog farm in Wazitang,De’an County,Jiujiang City,Jiangxi Province to explore the actual application effect of the ditch.Four groups of permeable interception dams were set up in the ditch to strengthen the ability of the ditch to intercept pollutants.The highest removal rate of TN can reach41.31%,the highest removal rate of NH₄⁺-N can reach 65.30%,the highest removal rate of TP can reach 35.15%,and the average removal rate of chemical oxygen demand（COD）is16.53%.