[Characterization of Microplastic Removal Rate Variation in the Whole Process of Urban Wastewater Plant with Conventional Oxidation Ditch Process].

Wastewater treatment plants （WWTPs） are considered to be the major source of microplastics entering natural water bodies， and research on microplastics in developing countries is still in its infancy. Taking Handan， a typical city in northern China， as the object， the characteristics of the removal rate of microplastics in the whole process of the first phase of a sewage treatment plant and the expansion project were studied. The results showed that： ① The shape of the wastewater microplastics was mainly fibrous microplastics， and the size of the wastewater microplastics was less than 0.5 mm. ② Among all levels of treatment， secondary treatment played a key role in the removal of microplastics. ③ The total removal rate of the first phase project and the expansion project in summer reached 90.20% and 84.75%， and the total removal rate in winter reached 93.75% and 82.50%， respectively. Despite such high removal efficiency， large amounts of microplastics were discharged into the final waters due to the large daily processing capacity. The purpose of this study is to provide theoretical guidance for the operation management of wastewater treatment plants to improve the removal rate of microplastics.