Microplastic contamination in water supply and the removal efficiencies of the treatment plants: A case of Surabaya City, Indonesia

Microplastics (MPs) have been recently detected in the Surabaya River, Indonesia, which is used as raw water for water supply. This condition has aroused concern about MP presence in the treated water in Surabaya drinking water treatment plants (DWTPs). This study aimed to investigate the MP abundance and characteristics of the raw and treated water and the removal efficiencies in each treatment unit in two selected Sub-DWTPs (SDWTPs) in Surabaya Water Supply Enterprise. These SDWTPs apply conventional technology comprising aeration, pre-sedimentation, coagulation, flocculation-sedimentation, filtration, and disinfection stages. The MP abundance values in the raw and treated water in SDWTPs I and II were 26.8–35 and 8.5–12.3 particles/L, respectively. The MP was dominated by 93–95% fiber in the raw water and 84–100% in the treated water. The MP dominant size in the raw and treated water was 351–1000 μm, with the percentages of 45–50 and 36–69%, respectively. The dominant polymer types of MPs in the raw water were polyethylene (PE), polypropylene (PP), and low-density polyethylene (LDPE). The total MP removal efficiencies in SDWTPs I and II were 54 and 76%, respectively.