Evaluation of microplastic removal efficiency of wastewater-treatment plants in a developing country, Vietnam

Wastewater-treatment plants (WWTPs) are considered significant point sources of microplastics (MiP) in the receiving waters; MiP release is poorly estimated in developing countries. MiP abundance, recovery efficiency and daily load to receiving waters were explored in treatment stage facilities of four WWTPs in Vietnam, located in Ho Chi Minh City, Thu Dau Mot, and Da Lat. MiP abundance varied from 1860 items m−3 to 125,000 items m−3 in influents and between 140 items m−3 and 813 items m−3 in the final effluents. The MiP-removal efficiency was the highest in the Da Lat wastewater-treatment plant (DL WWTP), a tertiary treatment plant using trickling filters followed by aerated lagoon and maturation ponds for BOD and nitrogen removals. The lowest MiP-removal efficiency was observed in Binh Hung wastewater-treatment plant (BH WWTP), a combined sewer system using conventional activated sludge processes as secondary treatment. The total daily MiP load to the receiving environment varied from 1,840,000 items d−1 at the DL WWTP to 77,127,000 items d−1 at the BH WWTP. Change in MiP abundance, morphology, and removal efficiency were discussed after each stage of the treatment process for the four WWTPs.