Tracking microplastics contamination in drinking water in Zahedan, Iran: From source to consumption taps

Microplastics (MPs) that pollute drinking water are inherently toxic, act as an adsorbent of hazardous pollutants, and threaten human health. So, the fate of microplastics in drinking water from the source to consumption taps (CTs) was assessed in spring and winter in Zahedan city in Iran. Sampling was performed from 4 reservoirs (raw water), before and after two water treatment plants (WTPs), and 10 CTs. The reservoirs were sampled using a plankton net (pore size = 100 μm), and the remaining samples were taken using a sampling device (containing a stainless steel membrane as a filter with pore size = 5 μm). The combination of density separation techniques, digestion, observation, Micro-Raman and FTIR, and SEM analysis was performed to recognize MPs. The average number of MPs in raw water varied between 15.4 and 44.7 MP/m³ (winter) and 22-51.8 MP/m³ (spring). The results before and after the treatment plant showed that about 64 % and 75 % of particles were eliminated in WTP₁ and WTP₂, respectively. The average number of MPs in CTs was more than treatment water (CT_a = 85-390 MP/m³ and CT_b = 75-400 MP/m³), which is a probable confirmation of secondary contamination (abrasion from pipes, installations, and sealing materials). The dominant type of polymer detected in raw water, treated water, and consumption taps were PS. The estimated daily intake for children and adults was about 0.16-15 MP/kg/bw/year and 0.07-5.7 MP/kg/bw/year, respectively. The surface morphology of MPs showed that the particles were affected by continuous weathering, mechanical breakage, and oxidation. MPs threaten the environment and human health due to the adsorption and transport of hazardous pollution and their intrinsic toxicity, so a solution must be thought of to prevent the pollution of drinking water by MPs.