| Microplastic is a new type of environmental pollutants that are difficult to degrade.They exist widely,have large specific surface area and are easy to adsorb toxic substances,which would cause direct or indirect damage to the ecological environment and biological health.Now,they have attracted extensive attention from scholars at home and abroad.At present,researches of microplastics are mainly focus on their ecological distribution,adsorption effecst and toxicity,explorations of their sources and trends are limited and need to be further studied and sorted out.The study on the distribution characteristics and migration rules of microplastics in wastewater provides a theoretical basis for improving the removal efficiency of microplastics in wastewater treatment plants and strengthening the prevention and control management.In this paper,by studying the distribution and removal efficiency of microplastics in the SBR process for wastewater treatment,two representative wastewater treatment plants in Yangzhou were investigated and studied-Yangzhou Tangwang Sewage Treatment Plant(CAST process,mainly treating domestic sewage)and Yangzhou Liuwei Sewage Treatment Plant(A2/O process,mainly treating industrial wastewater).The distribution and migration of microplastics in sewage treatment process were studied,and the difference of microplastics removal rate in different treatment processes was compared.Based on the research results,countermeasures and suggestions for microplastics emission reduction were put forward.The main conclusions of this paper are as follows:(1)The feasibility of Nile red staining method for identification of microplastics was verified,and the optimal dyeing conditions were determined.On this basis,the concentration,morphology and composition of microplastics were detected by the combination of Nile red staining method and infrared spectroscopic analysis method,which could not only efficiently,accurately and quantitatively identify microplastics,but also qualitatively analyze microplastics by spectroscopic analysis.The method is easy to operate and high detection efficiency.(2)The characteristics of microplastics in sewage were revealed.The main components of microplastics in the two sewage treatment plants are PP,PE and PS.In Tangwang Sewage Treatment Plant.the influent microplastics concentration was 7.8 pieces/L and effluent microplastics concentration was 1.4 pieces/L,and the removal rate was 82.05%.In Liuwei Sewage Treatment Plant,the influent microplastics concentration was 17.9 pieces/L.the effluent microplastics concentration was 2.0 pieces/L,and the removal rate was 88.83%.The influent microplastics concentration in Liuwei Sewage Treatment Plant was about 2.29 times that of Tangwang Sewage Treatment Plant.To some extent,this indicates that the content of microplastics in industrial wastewater is higher than that in domestic wastewater.(3)The removal efficiency of microplastics by different treatment processes was studied.The primary treatment efficiency of Tangwang and Liuwei Sewage Treatment Plant is 71.79%and 80.45%.The removal efficiency of secondary treatment was 31.82%and 37.14%,which was close to the removal efficiency of laboratory SBR process(31.25%).The removal rates of tertiary treatment were 6.67%and 9.09%.The research data show that the removal efficiency of microplastics is the highest in the first stage treatment.Microplastics are essentially suspended pollutants,so it can be combined with the process of removing suspended solids,such as the addition of activated carbon filter,air floating pool and other processes to improve the removal rate of microplastics.(4)In Tangwang and Liuwei Sewage Treatment Plants,the daily amount of microplastics discharged through sludge is 3-4 times that of sewage,which indicates that the microplastics in sewage migrate to sludge.Existing studies pay more attention to the discharge of microplastics in sewage,but the discharge of microplastics in sludge can not be ignored.(5)Based on the research results of this paper and domestic and foreign literature,suggestions on improving the wastewater treatment plant process and management opinions on reducing microplastics discharge are put forward,such as choosing the combination of air floatation,carbon filtration and other processes with coagulation and sedimentation.and strengthening the management of industrial wastewater discharge,so as to provide scientific basis for the removal and control of microplastics pollution. |
PDF Full Text Request