Occurrence and removal of microplastics from wastewater treatment plants in a typical tourist city in China

Wastewater treatment plants (WWTPs) serve as an important source of microplastics into the environment, but the factors affecting the distribution of microplastics remain unknown. To address this knowledge gap, four WWTPs in Guilin City, Guangxi Province, China were selected to analyze the dynamic distribution of microplastics in each wastewater treatment stage, of which, one used A/O process and the other three used A/A/O process. Results showed that the microplastic content in the WWTP influent was 0.70–8.72 items/L, in which 41.2–47.1% were removed during the pretreatment stage. Compared with the influent, the microplastic content in the final effluent decreased by 89.2–93.6%, dropping to 0.07–0.78 items/L. Microplastics in the size range from 500 μm to 5 mm dominated in the influent of each WWTP, and the proportion was even higher in the effluent. Fiber, fragment, and film were the main microplastic types found in the influent, but fibers were predominated in the effluent. Fragments and films were mainly composed of polypropylene (PP) and polyethylene (PE), while fibers had a more diverse compositions including PP, polyethylene terephthalate (PET), and polyacrylonitrile (PAN). Microplastics were also widely present in the sludge, with an abundance of 234.7–6908.3 items/kg dry weight. Correlation analysis showed that the tertiary industry is the main contributor of microplastics to WWTPs in Guilin City, providing direction for the future prevention and control of microplastics. [Display omitted] •MPs in wastewater were reduced by 89.2–93.6% through treatment.•The removal rate of fiber was significantly lower than that of fragment and film.•Fibers could bypass and escape through WWTPs.•MPs may cause environmental risks in the process of sludge resource utilization.