Accumulation and re-release of metallic pollutants during drinking water distribution and health risk assessment

Abstract

Heavy metals easily accumulate and re-release in drinking water distribution systems (DWDS), which greatly affects the safety of drinking water. The changes in eight metals (Al, Fe, Mn, Zn, Cu, Ba, Cr, and As) were investigated from the finished water (water treated by a drinking water treatment process before entering the distribution process) to the tap water of 10 water treatment plants in 5 cities of eastern China. The water quality of tap water was evaluated by measuring the metallic and non-metallic parameters. Correlation and principal component analysis (PCA) were used to reveal links among studied metals and identify the possible sources of metals. To assess the human risks associated with drinking water, the HQ (hazard quotient) values for single elements and HI (hazard index) were used. The metal concentration in the tap water was mostly higher than that in the finished water and almost no samples remained constant with finished water, indicating that the water quality could deteriorate during drinking water distribution in the studied areas. Both the HQ values and HI values for all studied elements were far below 1, indicating that there were negligible non-carcinogenic risks for inhabitants (adults and children) due to water intake. Carcinogenic risk values showed that the As concentration in the studied areas was up to 1.94 × 10⁻⁴ and this value was higher than 1 × 10⁻⁴. Trace amounts of As could accumulate in DWDS. There were obvious variations in the heavy metals between finished water and tap water, and the accumulation and re-release effects of metals in DWDS could not be ignored.