Research On Removal Of Mixed Pesticide By Iron-carbon Micro-electrolysis Coupled With Constructed Wetland System

The purpose of this thesis is to construct a mixed solution of organochlorine pesticides Chlorothalonil,a-endosulfan and ?-endosulfan,organophosphorus pesticide chlorpyrifos and pyrethroid pesticide deltamethrin in the iron-carbon micro-electrolysis coupled with constructed wetland system.?1?With the goal of removing the phosphate,COD and ammonia nitrogen in the wastewater and the improvement of biodegradability by iron-carbon filler,the single factor analysis method is used to optimize the preparation method of iron-carbon filler,and the preparation of iron-carbon filler is screened out.Screening the best ratio of iron powder and carbon powder for preparing iron carbon filler,the optimum content of kaolin,the best calcination temperature and the most suitable calcination time,and characterize its performance.?2?Construct two iron-carbon micro-electrolysis coupled with constructed wetland systems with identical conditions,select windmill grass and canna indica as wetland plants,and investigate the removal effect of phosphate,COD and ammonia nitrogen in different hydraulic retention time.The optimal wetland plants and hydraulic retention time required for the operation of the system were screened out,and subsequent studies on the removal of mixed pesticides were carried out.?3?The experiment uses artificial water distribution,and the mixed pesticides composed of organochlorine pesticide chlorothalonil,a-endosulfan and ?-endosulfan,organophosphorus pesticide chlorpyrifos and pyrethroid pesticide deltamethrin as the research object,comparative analysis of iron-carbon micro-electrolysis coupled with constructed wetland system and The removal capacity of mixed pesticides in traditional constructed wetland systems;and the comparative analysis of the removal effects of phosphate,COD and ammonia nitrogen by iron-carbon micro-electrolysis coupled with constructed wetland system and traditional constructed wetland system,at the end of each concentration phase of mixed pesticides,The cumulative concentrations of chlorothalonil,chlorpyrifos,endosulfan and deltamethrin in the plant tissues of the iron-carbon micro-electrolysis coupled with constructed wetland system and the traditional constructed wetland system,and the recovery period after the end of each dosing phase were respectively tested.Phosphate,COD and ammonia nitrogen removal.?4?To investigate the effects of mixed pesticides on the microbial community and the activities of urease,dehydrogenase,alkaline phosphatase,neutral phosphatase and acid phosphatase in the iron-carbon micro-electrolysis coupled with constructed wetland system,and combine with the the iron-carbon characteristics to research the removal mechanism of the system for mixed pesticides wastewater.Through this research,we can get the following conclusions:?1?In the preparation of iron-carbon filler,according to the removal of phosphate,COD,ammonia nitrogen and the improvement of biodegradability of wastewater,the best quality ratio of iron powder and carbon powder for making iron-carbon ceramics is 2:3.The optimum content of kaolin is 30%,the optimum calcination temperature is 900 ?,and the best calcination time is 4h.The prepared iron-carbon filler is a mesoporous material having sufficient compressive strength and relatively small specific surface area,and the adsorption capacity is relatively limited.?2?Under the same hydraulic retention time,the removal of phosphate,COD and ammonia nitrogen by the iron-carbon micro-electrolytic coupled constructed wetland system of planting canna was significantly better than the system of planting windmill grass.Therefore,the selection of canna as the wetland plant for subsequent experiments.The average removal rate of phosphate,COD and ammonia nitrogen in the system with 2 days of hydraulic growth was 16.59%,26.43%and 26.55%higher than the hydraulic retention time of 1 day,respectively,indicating that the system has a hydraulic retention time of 2 days.The removal of phosphate,COD and ammonia nitrogen is far superior to the one with a hydraulic retention time of one day.When the system hydraulic retention time is 3 days,the average removal rate of phosphate,COD and ammonia nitrogen is 4.10%,5.86%and 5.52%higher than the hydraulic retention time of 2 days,respectively,indicating that the system has phosphate retention time and COD for 3 days.The removal effect of ammonia nitrogen was slightly better than that of the hydraulic retention time of 2 days.Considering the factors of operation time and economic cost,the hydraulic retention time of the subsequent experiments was selected as 2 days.?3?When adding low-concentration mixed pesticides to the iron-carbon micro-electrolysis coupled with constructed wetland system and the traditional constructed wetland system,the iron-carbon micro-electrolysis coupled with constructed wetland system for chlorothalonil,?-endosulfan,?-endosulfan,The average removal rate of chlorpyrifos and deltamethrin was 6.38%,3.08%,5.60%,7.62%,6.30%higher than that of traditional constructed wetland systems,respectively.The average of phosphate,COD and ammonia nitrogen in the iron-carbon micro-electrolysis coupled with constructed wetland system.The removal rate was 31.14%,28.15%,and 37.22%higher than that of the traditional constructed wetland system.When the medium concentration of mixed pesticide was added to the two systems,the iron-carbon micro-electrolysis coupled with constructed wetland system to chlorothalonil and a-endosulfan The average removal rates of ?-endosulfan,chlorpyrifos and deltamethrin were 7.85%,6₃2%,8.77%,8.39%,and 11.88%,respectively,compared with the traditional constructed wetland system.The iron-carbon micro-electrolysis coupled with constructed wetland system was phosphate,The average removal rates of COD and ammonia nitrogen were 33.74%,33.42%,and 40.20%higher than those of traditional constructed wetland systems respectively.When adding high concentrations of mixed pesticides to two systems,the iron-carbon micro-electrolysis coupled with constructed wetland system to chlorothalonil,a-endosulfan,P-endosulfan,poison The average removal rate of dead cockroaches and deltamethrin was 9.38%,6.32%,8.77%,8.39%,11.88%higher than that of traditional constructed wetland systems,respectively.The average of phosphate,COD and ammonia nitrogen in the iron-carbon micro-electrolysis coupled with constructed wetland system.The removal rates were 40.24%,37.34%,and 43.31%higher than those of traditional constructed wetland systems,respectively.It is indicated that the removal effect of phosphate,COD and ammonia nitrogen by iron-carbon micro-electrolysis coupled with constructed wetland system is much better than that of traditional constructed wetland system,and the ability of iron-carbon micro-electrolysis coupled with constructed wetland system to resist the impact of mixed pesticides,the stability and the recovery of the system are better than the traditional constructed wetland system,the iron-carbon micro-electrolysis coupled with constructed wetland system has better continuous processing capacity for pollutants.?4?The iron carbon filler has no strong adsorption capacity for mixed pesticides,but it can provide guarantee for the continuous operation of the constructed wetland system,and decompose organic pollutants such as mixed pesticides through the microelectrolysis field,thereby improving the biodegradability of the mixed pesticides.The iron-carbon microelectrolysis coupled with the microorganisms in the constructed wetland system provides an attachment site,which is beneficial to the subsequent biodegradation of organic pollutants such as mixed pesticides,and maintains the efficient and stable operation of the system.And the iron carbon filler is beneficial to improve the removal effect of the system on phosphate.Before and after the mixed pesticides were added,the microbial community structure of the iron-carbon layer and the zeolite layer in the iron-carbon micro-electrolysis coupled with constructed wetland system changed significantly.Among them,the relative abundance of the iron-carbon layer was significantly changed by Proteobacteria and Enterobacter.Their relative abundance increased by 10.7%and 16.6%respectively.The relative abundance of zeolite layer was significantly changed by Acinetobacter and Enterobacter,and the relative abundance of Acinetobacter was reduced by 39.6%.The relative abundanc.e of Enterobacter increased by 42.5%.Chlorothalon il mainly relies on the degrad ation of Enterobacter,Pseudomonas,C.pallidum and Flavobacterium in the iron-carbon layerr.The chlorothalonil mainly relies on Enterobacter to degrade in the zeolite layer.Endosulfan in the iron-carbon layer mainly relies on Enterobacter,Pseudomonas,Bacillus,Flavobacterium,Acinetobacter and Bacillus;en dosulfan is main ly degraded in the zeolite layer by Enterobacter;Chlorpyrifos in the ion-carbon layer mainly depends on Entero;bacter,Acinetobacter,Flavobacterium and Pseudomonas,and Aeromonas is degraded.Chlorpyrifos is mainly degraded in the zeo lite layer by Enterobacter;deltameth rin It mainly relies on the Pseudomonas of the iron-carbon layer,which is degr aded by Bacillus,and the degradation of deltamethrin by the microo rganisms in the zeolite layer is very limited.The ammonia nitrogen in the system is mainly removed by the sph ingomonas and the genus Mycelium of the genus Taueus,Nitrospira,Hydrogenosporum and zeolite layers of the iron-carbon layer.The activity of urease,dehydrogenas.e,alkaline phosphatase,neutral ph osphatase and alkaline phosphatase in the zeolite layer in the system is higher than that of the iron-carbon layer,and urease and detachm ent in the system after adding the mixed pesticide The activities of five substrate enzymes,hydrogenase,alkaline phosphatase,neutral pho sphatase and alkaline ph osphatase,showed a decrease,which indicated that the addition of mixed pesticides had a greater impact and impact on the system matrix enzyme activity.