| Microplastics,an emerging contaminant,are pervasive in natural environmental media and organisms.Microplastics are potentially damaging to ecology and species due to their toxicity and coupled pollution with other pollutants.As a result,researchers are increasingly concerned about the problem of environmental pollution caused by microplastics.The Gulf has significant economic significance,and the safety of its products is particularly crucial.Wastewater treatment plants are an important sink and source of microplastics,industry is often mentioned as a source of microplastic pollution,some factory effluent will be further treated by sewage treatment plants,but a significant portion of factory effluent is treated by the internal sewage treatment system of factories and then directly discharged to the sea,and exploring the characteristics of microplastics in coastal sewage treatment plants and factories can provide a scientific basis for the research on the source-sink characteristics,migration,prevention and control of marine microplastics.The seasonal variation of microplastic pollution in the natural environment may be related to the seasonal change of microplastic emission in sewage treatment plants,so the seasonal changes of microplastics in sewage treatment plants are explored,which provides necessary data support for explaining the seasonal changes of microplastic pollution levels in natural environments.In this paper,sewage treatment plants and factories along the coast of Laizhou Bay and Jiaozhou Bay,typical bays in Shandong Province,were selected as research objects,the abundance and characteristic distribution of microplastics in municipal wastewater treatment plants and mixed wastewater treatment plants were studied,the differences in drought and rainy seasons of microplastics in sewage treatment plants were compared and analyzed,and the microplastic pollution in five different types of coastal factories was investigated.The main results achieved are as follows:1.We collected influent and effluent samples from municipal wastewater treatment plants and mixed wastewater treatment plants to analyze the characteristics of microplastic in different wastewater treatment plants.The main conclusions were as follows:(1)In municipal wastewater treatment plants and mixed wastewater treatment plants,the average abundance of microplastics in the influent water was 80.77 pieces per liter and 108.89 pieces per liter,respectively,while the average abundance in the effluent water was 19.05 pieces per liter and 22.97 pieces per liter.Compared with municipal wastewater treatment plants,the abundance of microplastics in wastewater from mixed wastewater treatment plants was higher,and the fluctuation range of microplastic abundance in wastewater from mixed wastewater treatment plants was greater due to the combination of the proportion of industrial wastewater and the type of industrial wastewater.Due to the complex source of mixed wastewater treatment plant influent,wastewater treatment plants can stabilize microplastic removal efficiency by modulating the wastewater treatment process.(2)Microplastic sizes in the influent of municipal wastewater treatment plants and mixed wastewater treatment facilities were significantly different,with greater microplastic sizes in the latter.The distribution of the other primary traits showed no appreciable variation,with fibrous,blue,PE,and PET as the dominant features.(3)Municipal wastewater treatment plants had an average microplastic removal rate of71.90%,while mixed wastewater treatment facilities had an average microplastic removal rate of 73.71%,both of which were efficient in removing microplastics from wastewater.2.To evaluate and assess the features of microplastics in wastewater treatment plants in various seasons,influent,effluent,and sludge samples were taken from wastewater treatment plants in two different seasons.The main results achieved are as follows:(1)In the influent water during the dry and rainy seasons,there were 102.52 pieces/L and 361.78 pieces/L of microplastics,respectively,and there were 15.30 pieces/L and 52.89pieces/L of microplastics in the effluent water.The amount of microplastics in both the influent and effluent water was significantly higher in the rainy season.There were significant differences between the distribution of microplastic color and size characteristics between the dry and rainy seasons,There are also significant dry and rainy season differences in the distribution of color and size characteristics of microplastics,with blue,≤ 300 μm predominating in the dry season and transparent,500-1000 μm predominating in the rainy season,which may be related to climatic conditions and human lifestyle changes.The seasonal fluctuations in the amount of microplastics in wastewater treatment plants’ effluent are one of the factors that contribute to the seasonal variations in the amount of microplastics in the marine environment.Wastewater treatment plants are significant point sources of marine microplastics.(2)In the sludge from the dry and rainy seasons,there were 36.00 pieces/g(d.w.)and47.97 pieces/g(d.w.),respectively,of microplastics.The abundance and characteristic distribution of microplastics in sludge did not differ significantly between the dry and wet seasons,the amount of microplastics per unit mass of sludge had some limits,and the sludge system was vulnerable to the sludge treatment process and the removal effect of various microplastic types.3.To examine the characteristics of microplastics in various industries,we collected influent and effluent samples from 11 representative industries in Shandong coastal textile and dyeing factories,paper and plastic manufacturing plants,gold mining plants,chemical plants,and shipbuilding industries.The main conclusions were as follows:(1)Due to the high volume of microplastics produced by industrial production processes that are discharged into industrial wastewater and the average removal rate of 59.86% for microplastics by industrial internal wastewater treatment systems,there are a lot of microplastics in industrial effluent.The characteristics of this microplastic content were highly compatible with those of marine microplastic pollution,and coastal industrial wastewater sources had a significant contribution to this problem.It is advised to increase the industrial internal wastewater treatment systems’ capacity to remove microplastics and decrease the release of microplastics from industrial sources from the standpoint of microplastics prevention and management.(2)In terms of microplastic pollution,textile dyeing and printing plants were the most problematic industrial types.The wastewater produced by these industries accounted for 20%of the volume of global wastewater,necessitating further strengthening of the control of microplastic pollution in textile dyeing and printing plants.(3)Compared the distribution of microplastic characteristics in different industrial wastewater and wastewater treatment plants,microplastics in influent from different industrial sources were similar in shape and composition,fiber was the dominant feature,PE and PET were the main components,and there were industry differences in size and color.The size of microplastics in plant wastewater is significantly bigger,and industrial effluents may introduce larger-sized microplastics into mixed wastewater treatment plants. |
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