Effects of a Granular Activated Carbon Bed Coupled with a Membrane Filtration Process on the Treatment Characteristics of Microplastics in Sewer Pipes

The introduction of microplastics (MPs) into water environments can be broadly categorized into non-point sources, including tire fragments, industrial paint, and dust, where the source of pollution is unidentifiable, and point sources, occurring in identifiable locations such as homes or factories. Hazardous substances stemming from these diverse pollutants accumulate in rainwater chambers along combined sewage conduits. Public sewage treatment plants collect MPs in rainfall-runoff and domestic sewage through sewage pipes. This study analyzes the behavior and properties of MPs during the treatment of combined sewage overflow using membrane filtration (MF) coupled with granular activated carbon (GAC). The study encompassed an average total rainfall of 13.5 mm, a duration of 9.1 h, and a rainfall intensity of 3.7 mm/h. The event mean concentrations for habitation ranged from 3.8 to 22.3 mgTOC/L, 0.841 to 2.695 mgT-N/L, 0.024 to 0.157 mgTP/L, 7.037 to 19.302 mgCl/L. Under conditions of GAC bed <4.0 m/h and MF process at 0.5 ㎥/㎡d, the distribution of MPs was 403 MP/L in the influent into sewer pipes and 80 MP/L in the effluent from the GAC-MF system. This indicates that the GAC-MF system achieved an efficiency of more than 80% in removing MPs, making it a highly effective process for MP removal. The GAC-MF system demonstrated superior performance, producing high-quality finished water and positioning itself as a recommended method for MP removal.