| The Taihu Lake Basin has a developed economy,while its significant water pollution makes it one of China’s ten key polluted watersheds to control.Taking the agricultural non-point source pollution control technology and the demonstration project in the Taihu Lake Basin as the object,this research combs and summarizes the achievements of the existing agricultural non-point source pollution control technology during the Eleventh Five-Year Plan to the Thirteen Five-Year Plan,and conducts subsequent follow-up evaluation.Based on studying the removal effect of traditional pollutants,we discuss the long-term law of technology application.Meanwhile,we study the occurrence characteristics and the interception effect by the typical agricultural non-point source pollution control technologies of emerging pollutants(microplastics)in agricultural non-point source pollution in the Taihu Lake Basin.This research provides technical support and storage for the deep treatment of water environmental pollution in the Taihu Lake Basin and the engineering control research of the emerging microplastic pollutant.The main conclusions of the thesis are as follows:(1)The subsequent on-site follow-up evaluation results show that:(1)After treatment of some typical non-point source pollution control technologies in planting industries,the removal rate of TN was 20.0%～70.0%,the removal rate of TP was40.0% ～ 90.0%,the removal rate of COD was 20.0% ～ 50.0%;After treatment of some typical non-point source pollution control technologies in the aquaculture industry,the removal rate of TN was 50.0% ～ 92.0%,the removal rate of TP was65.0%～98.0%,the removal rate of COD was 40.0%～90.0%;The effluent treated by some typical rural domestic sewage pollution control technologies meets the first-level pollutant emission standards of rural domestic sewage treatment facilities,The effluent treated from farmhouse meets the first-level B pollutant emission standards of urban sewage plants.On the whole,Pollution control of planting,aquaculture and rural domestic sewage,the effluent from the initial stage of technology research and development and after 1-2 years of operation all meet the technical assessment requirements.(2)From the actual operation of the site,most of the agricultural non-point source pollution control demonstration projects in the Taihu Lake Basin are running well and well maintained,which greatly reduces the concentration of nitrogen,phosphorus and COD;However,there are still some demonstration sites that are poorly regulated and lack maintenance in later periods,resulting in the shutdown of the projects.Rural domestic sewage in some areas has been transported into the urban sewage treatment plant for treatment.(2)The more intensive human activity and the more developed industries in the Taihu Lake Basin,the higher the content of microplastics in surface rivers and lakes.Strips,flakes,and granules in all microplastic samples accounted for 58.8%,26.5%,and 14.7%,respectively.The morphology of microplastics in all the sampling sites is mainly strips.The content of microplastics with a particle size less than or equal to 2mm is the largest in the microplastic samples,accounting for 83.3%.Large-particle microplastics are prone to be produced in places with large people flow and large usage of plastic products.Among all microplastic samples,PET has the most content,accounting for 42.0%,followed by PP,accounting for 14.0%.(3)In the process of agricultural non-point source pollution control in the Taihu Lake Basin,the microplastics concentration of influent is much higher than that of other water bodies in the Taihu Basin,which is 10.00/(5L).Among them,the concentration of microplastics in the influent of non-point source pollution control technology for aquaculture in Taihu Lake Basin is the highest,with an average of58.33 /(5L);Rural domestic sewage followed,33.00 /(5L);The planting industry is the lowest,14.50 /(5L).The removal rates of micro plastics after treatment by classical planting industry,aquaculture industry and rural domestic sewage non-point source pollution control technology were 47.1%,67.8% and 63.1% respectively.In the process of agricultural non-point source pollution control in Taihu Lake Basin,the main form of influent micro plastic is strip,which is much higher than other forms(sheet and granular).The particle size of micro plastics is mainly less than 2 mm,among which the particle size of micro plastics in non-point source pollution of aquaculture industry is the largest,ranging from 0.01 mm to 2.80 mm,followed by rural domestic sewage(≤2.00 mm),and the lowest(≤0.80 mm)in planting industry;the particle size of microplastics in the effluent of these pollution control technologies is generally smaller than that in the influent.The microplastics are mainly PET,PE and Cellophane in inflow and outflow of non-point source pollution control technology of planting industry;PET,PP and PE in inflow of the non-point source pollution control technology of breeding industry and PET,PE,Cellophane in outflow;composed of PET,PP,PE and Cellophane in inflow and outflow of rural domestic sewage pollution control technology.However,the distribution of microplastics in different regions and different technologies has certain differences. |
