Performance of conventional activated sludge (CAS) and aerobic granular sludge (AGS) reactors for microplastics removal during municipal wastewater treatment

摘要

The contamination of plastics less than 5 mm in aquatic environments is gaining increasing attention, and several studies have identified microplastics in effluents of wastewater treatment plants. However, there has been limited research on the mechanism of microplastics removal during wastewater treatment, which could be critical in selecting an appropriate treatment technology that limits microplastics pollution. In this study, the mechanism of microplastics removal in two treatment processes, the conventional activated sludge process (CAS) and the aerobic granular sludge (AGS) process, was examined and compared using lab-scale reactors. The hypothesis was that AGS will retain more microplastics compared to CAS due to the higher extracellular polymeric substance (EPS) content of AGS. Microplastics were quantified in the influent and effluent wastewater using epifluorescence microscopy, while adsorption to EPS was observed through EPS staining and confocal microscopy. Results of this study showed that AGS removed more microplastics in the 75-90 μm range than CAS. Microplastics were also observed to be attached mostly to the protein component of EPS.