Study On Iron Carbon Microelectrolysis Intensification-Ecological Field Bund Technology Controlling The Agricultural Non-Point Source Pollution In Chongqing Section Of The Three Gorges Reservoir Region

With the advancement of environmental protection work in China,point source pollution has been effectively controlled and the proportion of non-point source pollution has become larger and larger.Therefore,non-point source pollution control has become a hot issue in China water environment governance.In rural areas,non-point source pollution mainly includes:farmland runoff,village rainwater surface runoff,etc.and agricultural non-point source pollution caused by farmland runoff is a key issue in rural ecological environment governance.As a source control technology for non-point source pollution of farmland,field bund has gradually received attention.Aiming at the problem of agricultural non-point source pollution in the Chongqing section of the Three Gorges Reservoir,this study adopted material characterization methods,simulated column dynamic studies,molecular biological detection methods and lateral seepage operation simulation studies to discuss the matrix properties,key parameters,microbial composition and lateral infiltration treatment effects of ecological field bund.The purpose is to determine the key structural parameters of ecological field bund and clarify its treatment effects and characteristics,and then put forward the engineering design plan of ecological field bund in the Chongqing section of The Three Gorges Reservoir Region.The following results were obtained through the study of the properties of the ecological ridge formation matrix.The soil is sandy loam with a rough surface and a p H of 6.1,which is slightly acidic.The charcoal has a porous structure with a particle size of 1?2 mm,in which the content of C element is81.29%.The particle size of iron is 0.4?0.6 mm and the main component is iron.These help to adsorb pollutants,form micro-batteries and provide a living space for microorganisms,thereby enhancing the effect of reducing pollutants.The following results were obtained through the dynamic study on the simulated field of ecological field bund.The ratio of carbon to iron and the thickness of the iron-carbon layer have a greater effect on nitrogen reduction.The removal rate of TN and NO₃^--N increased with the increase of carbon-to-iron ratio.The removal rate of TN and NH₄⁺-N increases with the thickness of the carbon-iron layer.Combined with the cost of the filler,it was determined that the optimal carbon-to-iron ratio was 2:1 and the optimal carbon-iron layer thickness was 20 cm.Flow and pollution load also have a certain effect on the reduction effect of ecological field bund.At three inlet flow rates of 0.5,1.0,and 1.5 m L/min,the TP removal rate exceeded 98%and the removal rates of COD,TN,and NH₄⁺-N decreased slightly with the increase of the inlet flow rate,and the removal rates were 87.04?93.22%,76.18%?86.31%and 84.86%?88.21%,respectively.Under the three pollution loads,the TP and NH₄⁺-N effluent concentrations are relatively stable,and the reduction rates are above 84%and 98%,respectively.The COD and TN increase slightly with the increase of the pollution load and the removal rates are 82.0%?89.1%and 73.6%?83.9%,respectively.According to molecular biology tests,the substrate contains Proteus bacteria?29.98%?,Chlorella bacteria?19.61%?and Bacteroides bacteria?1.67%?.These bacteria are important for the removal of nitrogen and organic matter.Through the simulation study on the lateral seepage operation of the ecological field bund,the treatment effect of the ecological field bund on the simulated farmland runoff was verified.The results show that the reduction rates of COD,TP,TN and NH₄⁺-N are all over 80%and the removal effect is better.Based on the removal effect of the lateral seepage operation of the ecological field bund,for the typical farmland in the Chongqing section of the Three Gorges Reservoir Region,an ecological field bund of 4000 m2 gently sloping farmland and an ecological ridge of 1200 m2 terraced fields are designed.The removal rate of COD,TN and NH₄⁺-N is expected to be over 80%,the removal rate of TP can reach more than 90%,and the service life is 3?4 years.