From source to distribution channel: A baseline study of microplastic occurrence in drinking water in Ogun State, Nigeria

Abstract

Microplastics (MPs) are emerging contaminants known to have contaminated not only surface and groundwater but also drinking water treatment plants (DWTPs) and tap water. Little is known about the occurrence of MPs in DWTPs in Africa, particularly in developing countries like Nigeria. To address this knowledge gap, this study investigated the prevalence and estimated daily intake of MPs in raw water, DWTPs, and tap water in a semi-urban area in Ogun State, Nigeria. Using Rose Bengal staining and optical microscopy, MPs in water samples were identified and characterised using standard methods. The abundances of MPs were 16.13 ± 3.83 particles/L in raw water, 10.74 ± 3.76 particles/L in treated water, and 12.43 ± 3.92 particles/L in tap water. Most of the MPs found in the water samples were classified as fibres, followed by fragments, with a size of < 1 mm. This study showed that the drinking water treatment plant reduced microplastics from raw water by 40%, however, there was an increase in the abundance of MPs in tap water. Residents estimated daily consumption of MPs from tap water varied between 0.31 and 0.44 particles for adults and between 1.2 and 1.69 particles for children. This study addresses a critical gap in understanding microplastic pollution in the water distribution systems and DWTPs. The results also indicated that MPs were not effectively removed, requiring a more sophisticated treatment method to lower human exposure to MPs through drinking water from DWTPs.

Keywords: Drinking water treatment plants; Estimated daily intake of microplastics; Microplastics; Raw water; Tap water.