Microbial diversity, ecological networks and functional traits associated to materials used in drinking water distribution systems

Abstract

Drinking water distribution systems host complex microbial communities as biofilms that interact continuously with delivered water. Understanding the diversity, behavioural and functional characteristics will be a requisite for developing future monitoring strategies and protection against water-borne health risks. To improve understanding, this study investigates mobilisation and accumulation behaviour, microbial community structure and functional variations of biofilms developing on different pipe materials from within an operational network. Samples were collected from four pipes during a repeated flushing operation three months after an initial visit that used hydraulic forces to mobilise regenerating biofilms yet without impacting the upstream network. To minimise confounding factors, test sections were chosen with comparable daily hydraulic regimes, physical dimensions, and all connected straight of a common trunk main and within close proximity, hence similar water chemistry, pressure and age. Taxonomical results showed differences in colonising communities between pipe materials, with several genera, including the bacteria Pseudomonas and the fungi Cladosporium, present in every sample. Diverse bacterial communities dominated compared to more homogeneous fungal, or mycobiome, community distribution. The analysis of bacterial/fungal networks based on relative abundance of operational taxonomic units (OTUs) indicated microbial communities from cast iron pipes were more stable than communities from the non-ferrous pipe materials. Novel analysis of functional traits between all samples were found to be mainly associated to mobile genetic elements that play roles in determining links between cells, including phages, prophages, transposable elements, and plasmids. The use of functional traits can be considered for development in future surveillance methods, capable of delivering network condition information beyond that of limited conventional faecal indicator tests, that will help protect water quality and public health.

Influence of phosphate dosing on biofilms development on lead in chlorinated drinking water bioreactors

“…This is in agreement with other studies where fungal communities in drinking water biofilms tended to be less diverse and more stable over time 73 when compared with bacteria. From this study, we can confirm that fungi formed part of mix-species consortia with bacteria in biofilms, being an important component of the microbial communities of lead and PVC materials in DWDS 73,74 . Despite fungi are not usually included in drinking water regulations, the monitoring of these organisms should be considered by water utilities due to their involvement in processes that can deteriorate water quality.…”

“…Bacteria belonging to the genera Sphingomonas, Afipia and Acidovorax, and fungal genera such as Exophiala, Cadophora and Fusarium, were detected in all the conditions and materials studied. It can be suggested that these microorganisms form a core community and play a key role in biofilm formation, as proposed by other researchers studying mixed-species biofilms [72][73][74][75][76][77] . In these studies, bacteria belonging to the genera Acinetobacter, Burkholderia, Methylobacterium, Mycobacterium, Sphingomonas and Staphylococcus played an important role in the formation of biofilms an aggregates [78][79][80][81] .…”

“…For fungal characterisation, the ribosomal internal transcribed spacer regions ITS1-2 were targeted. Sequence data was processed by MR DNA using as described in Douterelo et al 74 . The number of shared genera between samples and the Venn diagrams was calculated using the web tool provided by the Bioinformatics & Evolutionary Genomics group at the University of Gent (http://bioinformatics.psb.ugent.be/webtools/Venn/).…”

Factors Shaping Young and Mature Bacterial Biofilm Communities in Two Drinking Water Distribution Networks

“…More than 98% of the total biomass present in DWDS have been found to be present as biofilms and loose deposits in an unchlorinated DWDS as quantified by adenosine triphosphate (ATP) analysis and DNA-pyrosequencing (Liu et al 2014). There is limited access to operating water main pipes and hence, most prior studies have been conducted on premise plumbing systems including i) mature pipe biofilms in buildings designated to be demolished (Henne et al 2012), ii) biofilms within replaced water meters (Ling et al 2016), and iii) young sentinel biofilms growing on carrier coupons in model systems (Douterelo et al 2014) or fire hydrant outlets (Douterelo et al 2020).…”

Impact of coagulation–ultrafiltration on long-term pipe biofilm dynamics in a full-scale chloraminated drinking water distribution system

“…To address this difficulty, studies have investigated different types of biofilms in the DWDS that are more accessible, including biofilm on water meters 8 and coupons recovered from pilot-and full-scale systems, 9,10 as well as estimations of the biofilm community by sampling water at different locations in the DWDS. 11,12 Grab samples of pipe biofilm, obtained for research purposes or during pipe maintenance, have also been investigated. 1,8,[13][14][15] Maintaining disinfectant residuals such as chloramine to repress growth of problematic organisms in the DWDS is common practice.…”