Investigation On Distribution Characteristics And Treatment Strategies Of Microplastics Pollution In Typical Water Environment Of Hefei City

Plastic products are widely used because of their excellent performance and low cost.After discarded,plastics often lack proper recycling and management leading to increasing gradually of the concentration level of microplastics in the natural environment.This situation has affected the sustainable development of the ecological environment to a certain extent.In recent years,a growing number of studies has proved the potential threat of microplastics to human health.Based on the imminent treatment of microplastics pollution in urban water environment,it is necessary to study the distribution characteristics and potential risks of microplastics in divers urban water environment.Taking Hefei as an example,this work investigated the pollution of microplastics in its urban river（Nanfei River）and wastewater treatment plant,and selected a kind of commonly used industrial bacteriostatic agent（methylparaben）as the research object to investigate the adsorption and enrichment ability of microplastics.Finally,combined with the above research results,the precautions of microplastic pollution control in urban water environment were put forward.The main conclusions were as follows:（1）The concentrations of microplastics in the upstream and downstream of the Nanfei River,tributaries and main streams showed significant differences（P<0.05）.The concentration ranged from 0.80 to 27.00 items/L（the average concentration was 10.92±8.47items/L）.The main shapes,colors,and sizes of microplastics were pellets,white,and 50～333μm,respectively.PE and PP are the main polymer types in the microplastics sampled.The ecological risk assessment based on polymer type showed that the microplastic pollution in Nanfei River was at an upper medium risk level,while the ecological risk assessment based on concentration showed a low risk level.Wastewater treatment plants were the most critical way for microplastics to enter the water environment,and could significantly affect the level of microplastics in surrounding rivers.Conventional environmental management measures can effectively control microplastic pollution to a large extent,reducing the possibility of microplastics entering from upstream or tributaries to downstream,thereby reducing the level of microplastic pollution in sections.（2）The concentrations of microplastics in the raw water of the three wastewater treatment plants around Nanfei river were 76.6±2.5,67.3±4.0,98.7±7.7 items/L,and the effluent concentrations were 14.8±0.6,17.2±0.6,23.0±0.4 items/L,which means that the highest removal rate could reach 80.68%.The primary treatment showed a more prominent microplastic removal ability than the secondary treatment and the tertiary treatment.Although the microplastics in the three wastewater treatment plants were mainly PE,PP,and PS,the diversity of microplastics in the two wastewater treatment plants deviated from the city center is higher than that of the wastewater treatment plant in the city center.In addition,the level of potential risk to the urban water environment from the wastewater treatment plant in suburban areas is much higher than that of wastewater treatment plants in urban areas.（3）The study on the synergistic effect of microplastics and methylparaben indicated that microplastics can adsorb methylparaben.PVC,PET,PE and PS were mainly physical adsorption,including electrostatic interaction,hydrogen bond formation and π-π bond formation.The adsorption rate was jointly controlled by internal diffusion and external diffusion.High salinity,high pH and metal ions would inhibit the adsorption,while low size and low pH could promote the adsorption.Among them,PVC has stronger adsorption capacity because of halogen in its molecules,and the theoretical maximum adsorption capacity was 1.269,1.038,0.769 and 0.656 mg/g respectively.（4）At present,there are promising microplastic pollution control policies and technical environment around the world.In this regard,the governance idea could be proposed that reducing the production and use of plastic products supplemented by developing biodegradation technology and improving the removal efficiency of microplastics in wastewater treatment plants to alleviate microplastic pollution in urban water environment.The related research results of this study can provide reference for other cities in microplastics pollution research and governance system construction,contributing to China’s ecological civilization construction.