Microplastic characterization and removal efficiency in wastewater treatment plants with diverse influent sources in Uganda

Wastewater treatment plants (WWTPs) are significant sources of microplastic (MP) pollution due to widespread plastic use and their limited ability to remove contaminants. This study examined MP levels, characteristics, and removal efficiency in both raw and processed wastewater from Lubigi WWTP, which handles both piped sewage and fecal sludge from private cesspools such as pit latrines and septic tanks, through waste stabilization ponds. The second facility, Bugolobi WWTP, mainly treats domestic wastewater from septic tanks and surface runoff via city drainage, using physical, chemical, and biological treatment methods. Influent MP concentrations were 5,290 ± 605 particles per liter at Lubigi and 14,280 ± 1,057 particles per liter at Bugolobi; effluent levels were 760 ± 69 and 1,160 ± 158 particles per liter, with removal efficiencies of 74 ± 23% and 83 ± 2.8%, respectively. Beads and fragments predominated in influents, whereas films increased in effluents. Larger particles (150–250 µm) were more common in influents, while smaller particles (< 150 µm) mainly appeared in effluents. The primary polymers identified were polyethylene terephthalate (67%) and polyamide (33%). These findings emphasize the need to enhance MP removal processes in Ugandan WWTPs.