Microplastics are effective carriers of bisphenol A and facilitate its escape from wastewater treatment systems

Microplastics (MPs) pollution is a major issue in aquatic environments. Wastewater treatment plants are significant point sources of MPs, which may also be carriers of organic pollutants. We analyzed MP number, shape, color, and polymer type distribution in sewage wastewater treatment plants. The potential of MPs to act as carriers for typical organic pollutants in sewage, such as bisphenol A (BPA), was also assessed. The predominant MPs in the influent were fibers, primarily transparent and black in color, and composed of polyethylene, polypropylene, and polystyrene. During wastewater treatment, the concentration of MPs decreased from 10.89 items per L in the influent to 0.89 items per L in the treated effluent, with significant differences in treatment efficiency at different stages. In the simulated wastewater, the three predominant MPs exhibited certain adsorption capacities for bisphenol A. Changing the temperature and pH within the range expected for wastewater could interfere with the interactions between MPs and bisphenol A, with a limited impact on adsorption. The results show that although wastewater treatment plants intercept a significant amount of MP, a considerable number of them enter the aquatic environment daily because of the high volume of wastewater discharge. These MPs, which carry pollutants such as bisphenol A, may threaten the health of fish and other aquatic organisms. However, by scientifically adjusting operational parameters, wastewater treatment plants could become "controllable sources" of MP compound pollutants.