Alternative for HPC22 after repairs in the drinking water distribution system

“There is a risk of contamination by (pathogenic) microorganisms from the outside environment into the drinkingwater during maintenance or pipe breaches in the drinking water distribution system (DWDS) and, consequently,the drinking water distributed to consumers may result in possible detrimental effects on public health. Tradi-tional time-consuming microbiological testing is, therefore, performed to confir drinking water is not micro-bially contaminated. This is done by culturing methods of the faecal indicators Escherichia coli, intestinalenterococci and the technical parameters coliform bacteria and heterotrophic plate counts at 22 ◦C (HPC22). Inthis study, fast methods (adenosine triphosphate (ATP), flo cytometry, enzyme activity and qPCR) werecompared as an alternative for HPC22. Using dilution series and fiel samples, ATP (ATPtotal-lab and ATPcell-mob) and enzymatic activity (ALP-2) methods proved to be the more reliable and sensitive than flo cytometry and qPCR methods for detecting microbiological contaminations in drinking water. Significan (p < 0.05) and relatively strong correlations (R2 = 0.61–0.76) were obtained between HPC22 and both ATP methods, enzymeactivity and qPCR parameters, but relations with flo cytometry were weak (R2 = 0.24 – 0.52). The samples taken after repairs or a calamity from the DWDS showed in general limited variation in the HPC22 count andwere in most cases below the guidance level of 1,000 CFU/mL. We recommend that the best performing alter-native methods, i.e. ATPtotal-lab and ATPcell-mob and ALP-2, should be included next to HPC22 in additional file studies to further test and compare these methods to be able to decide which fast method can replace HPC22 analysis after maintenance work in the DWDS." (Citation: Waals, M. van der, Bel, N. van, Charante, F. van, et.al. - Alternative for HPC22 after repairs in the drinking water distribution system - Water Research 265(2024)art. no. 122264 - DOI: 10.1016/j.watres.2024.122264 - (Open Access)) © 2024 The Author(s). Published by Elsevier Ltd. This article is available under the Creative Commons CC-BY-NC-ND license