Abstract
The microbial monitoring of drinking water production systems is essential to assure water quality and minimize possible risks. However, the comparative impact of microbes from the surrounding aquifer and of those established within drinking water wells on water parameters remains poorly understood. High pressure jetting is a routine method to impede well clogging by fine sediments and also biofilms. In the present study, bacterial communities were investigated in a drinking water production system before, during, and after hydraulic purging. Variations were observed in bacterial communities between different wells of the same production system before maintenance, despite them having practically identical water chemistries. This may have reflected the distinct usage practices of the different wells, and also local aquifer heterogeneity. Hydraulic jetting of one well preferentially purged a subset of the dominating taxa, including lineages related to Diaphorobacter, Nitrospira, Sphingobium, Ralstonia, Alkanindiges, Janthinobacterium, and Pseudomonas spp, suggesting their tendency for growth in well-associated biofilms. Lineages of potential drinking water concern (i.e. Legionellaceae, Pseudomonadaceae, and Acinetobacter spp.) reacted distinctly to hydraulic jetting. Bacterial diversity was markedly reduced in drinking water 2 weeks after the cleaning procedure. The results of the present study provide a better understanding of drinking water wells as a microbial habitat, as well as their role in the microbiology of drinking water systems.
Highlights
The need to protect drinking water from microbiological risks has been recognized for many years and strict regu lations regarding the monitoring and maintenance of public drinking water production systems are in place [39]
The microbiome of drinking water produced from groundwater is primarily influenced by the in flux of microbes from the surrounding aquifer, as well as by biofilms established in the drinking water wells and distri bution network itself
Extensive research has been performed on microbes in drinking water systems, information regarding the ecology of groundwater extraction wells as a microbial habitat is limited
Summary
The need to protect drinking water from microbiological risks has been recognized for many years and strict regu lations regarding the monitoring and maintenance of public drinking water production systems are in place [39]. Natural sediments are assumed to be restricted to patchy, monolayer communities [19], drinking water networks can experience substantial biofilm growth and the related unwanted effects, e.g. corro sion, clogging, or pathogen survival [2, 9, 35] These biofilms are continuously seeded by incoming aquifer microbes, and develop their own niches and specific hydrochemical environments [38]. Hydraulic well restoration by high pressure jetting is a routine maintenance method in porous aquifers that can be used to maintain well productivity in drinking water produc tion by dislodging inorganic and organic deposits in the well casing [7] This purging event offers a unique possibility to access the microbes established in the well vicinity and dis criminate them against the base influx of microbes from the surrounding aquifer. The application of 454 pyrotag sequencing of bacterial 16S rRNA gene amplicons [30] to suspended microbes allowed for an extensive level of detail on the microbiota in this oligotrophic habitat
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