Environmental DNA surveillance of biocontamination in a drinking water treatment plant.

A clean and adequate supply of drinking water is essential to life and good health. However, despite the risk of biologically derived contamination of drinking water, monitoring of invertebrate outbreaks has relied primarily on naked-eye inspections that are prone to errors. In this study, we applied environmental DNA (eDNA) metabarcoding as a biomonitoring tool at seven different stages of drinking water treatment, from prefiltration to release from household faucets. While the composition of invertebrate eDNA communities reflected the communities of the source water in earlier stages of the treatment, several predominant invertebrate taxa (e.g., rotifer) were shown to be introduced during purification, but most were eliminated in later treatment stages. In addition, the limit of detection/quantification of PCR assay and read capacity of high-throughput sequencing was assessed with further microcosm experiments to estimate the applicability eDNA metabarcoding to the biocontamination surveillance in drinking water treatment plants (DWTPs). Here we propose a novel eDNA-based approach for sensitive and efficient surveillance of invertebrate outbreaks in DWTPs.