A microbiology-based multi-parametric approach towards assessing biological stability in drinking water distribution networks

Abstract

a b s t r a c tBiological stability of drinking water implies that the concentration of bacterial cells and composition of the microbial community should not change during distribution. In this study, we used a multi-parametric approach that encompasses different aspects of microbial water quality including microbial growth potential, microbial abundance, and microbial community composition, to monitor biological stability in drinking water of the non-chlorinated distribution system of Zü rich. Drinking water was collected directly after treatment from the reservoir and in the network at several locations with varied average hydraulic retention times (6e52 h) over a period of four months, with a single repetition two years later. Total cell concentrations (TCC) measured with flow cytometry remained remarkably stable at 9.5 (AE 0.6) Â 10 4 cells/ml from water in the reservoir throughout most of the distribution network, and during the whole time period. Conventional microbial methods like heterotrophic plate counts, the concentration of adenosine tri-phosphate, total organic carbon and assimilable organic carbon remained also constant.Samples taken two years apart showed more than 80% similarity for the microbial communities analysed with denaturing gradient gel electrophoresis and 454 pyrosequencing.Only the two sampling locations with the longest water retention times were the exceptions and, so far for unknown reasons, recorded a slight but significantly higher TCC (1.3 (AE 0.1) Â 10 5 cells/ml) compared to the other locations. This small change in microbial abundance detected by flow cytometry was also clearly observed in a shift in the microbial community profiles to a higher abundance of members from the Comamonadaceae (60% vs.2% at other locations). Conventional microbial detection methods were not able to detect changes as observed with flow cytometric cell counts and microbial community analysis. Available online at www.sciencedirect.com journal home page: www.elsevier.com/loca te/watres w a t e r r e s e a r c h 4 7 ( 2 0 1 3 ) 3 0 1 5 e3 0 2 5 0043-1354/$ e see front matter ª

Core-satellite populations and seasonality of water meter biofilms in a metropolitan drinking water distribution system

“…Drinking water distribution system microbiota F Ling et al (Lautenschlager et al, 2013;Pinto et al, 2014). Furthermore, it is interesting to note that members of Comamonadaceae have been observed as dominant groups in biofilm and suspended communities of other fast-flowing, low-temperature and oligotrophic aquatic ecosystems including glacier-fed streams and headwater streams (Wilhelm et al, 2013;Besemer et al, 2012), suggesting that DWDS ecosystem shares similarities with other freshwater ecosystems in nature despite its engineered properties.…”

“…Most analyses of the microbiota in drinking water distribution systems (DWDSs) have focused on the suspended community (Lautenschlager et al, 2013;Pinto et al, 2014). Investigations of biofilms are difficult because of limited access and high cost involved in sampling.…”

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