Microplastics in drinking water. Efficiency of treatment and distribution of a drinking water cycle

Abstract

It is known that there are many sources of microplastics (MPs) contamination in reservoir water catchment areas. In addition, sampling, analysis, and determination techniques are not standardized, making not only sampling complicated, but also the comparison and extrapolation of the data obtained with other studies. This is further magnified in the determination in drinking water matrices. Furthermore, among the legislative aspects, introduces for the first time at the watch list about pollutant to be consider. Therefore, the objective of this study is to know the presence of MPs in the drinking water distribution cycle (natural reservoir (S1), outflow of the drinking water treatment plant (S2), city's reservoir (S3) and a municipal control point of the supply network (S4)), for this purpose a method for the analysis and determination of MPs in drinking water is set up and proposed. In order to carry out the study, several samples were taken at different points of the drinking water distribution pathway. Based on the shape of the particles, the result shows the predominance of fragments over fibers and bulk. A difference is observed between these forms between incoming (S1) and outgoing samples (S2 to S4); while in S1 it seems that fiber predominates over bulk, in S2 bulk predominate and in less concentration fibers. In S3 and S4 the tendency is similar to the S2, there is a predominance of fragment followed by bulk and finally fibers. Regarding the abundance of these polymers, it was 1550 ± 891 MP/m³ at S1, 115 ± 35 MP/m³ at S2, 435 ± 120 MP/m³ at S3 and 450 ± 221 MP/m³ in S4. These results show that is able to establish an average efficiency of the 92 ± 2 % removal of MPs in the purification processes. Likewise, regarding the typology of polymers, the most representative were PTFE, PE and PS. The amount of MPs is higher at the DWTP inlet than at the outflow, indicating that the treatment may reduce them, even if not specifically designed to do so. This study, conducted in a DWTP with conventional treatment, suggests these findings could apply to other similar plants. An increase in MPs has been noted from the DWTP outlet to the storage tanks and the city's distribution network, possibly due to material carryover and pipe wear.