Microplastic Removal Efficiency of Four Wastewater Treatment Processes in Kunming: Mechanisms and Optimal Process Selection

With the mass production and use of plastic products, Microplastic (MP) pollution is worsening due to widespread plastic use. Urban wastewater treatment plants (WWTPs) fail to fully remove MPs, making their effluents a key source of aquatic MP pollution. This study compared MP removal efficiencies across four Kunming WWTPs using different processes (AAO-V, BIOCOS-D, AAO-MBR, AAO-D filters) to identify optimal treatments for future plants. Removal efficiencies ranked: AAO-MBR (99.9%) > BIOCOS-D (96.1%) > AAO-D (92.1%) > AAO-V (88.6%). AAO-MBR showed the highest efficiency, with biofilm filtration and adsorption as the main removal mechanisms. Future WWTP design should prioritize high MP removal efficiency alongside nitrogen and phosphorus removal, with AAO-MBR recommended as the optimal process. The removal rate of MPs should be properly considered along with those of nitrogen and phosphorus when developing future wastewater plants, and processes with high MP removal rates should be selected when possible.