Microbial Community Dynamics of an Urban Drinking Water Distribution System Subjected to Phases of Chloramination and Chlorination Treatments

Abstract

Water utilities in parts of the U.S. control microbial regrowth in drinking water distribution systems (DWDS) by alternating postdisinfection methods between chlorination and chloramination. To examine how this strategy influences drinking water microbial communities, an urban DWDS (population Х 40,000) with groundwater as the source water was studied for approximately 2 years. Water samples were collected at five locations in the network at different seasons and analyzed for their chemical and physical characteristics and for their microbial community composition and structure by examining the 16S rRNA gene via terminal restriction fragment length polymorphism and DNA pyrosequencing technology. Nonmetric multidimension scaling and canonical correspondence analysis of microbial community profiles could explain >57% of the variation. Clustering of samples based on disinfection types (free chlorine versus combined chlorine) and sampling time was observed to correlate to the shifts in microbial communities. Sampling location and water age (<21.2 h) had no apparent effects on the microbial compositions of samples from most time points. Microbial community analysis revealed that among major core populations, Cyanobacteria, Methylobacteriaceae, Sphingomonadaceae, and Xanthomonadaceae were more abundant in chlorinated water, and Methylophilaceae, Methylococcaceae, and Pseudomonadaceae were more abundant in chloraminated water. No correlation was observed with minor populations that were detected frequently (<0.1% of total pyrosequences), which were likely present in source water and survived through the treatment process. Transient microbial populations including Flavobacteriaceae and Clostridiaceae were also observed. Overall, reversible shifts in microbial communities were especially pronounced with chloramination, suggesting stronger selection of microbial populations from chloramines than chlorine.

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

“…We hypothesize that seasonal water temperature fluctuation is the likely reason (Supplementary Figure S1B); however, further Drinking water distribution system microbiota F Ling et al studies are needed for better elucidation. Other engineering factors examined in this study did not appear to affect the biofilm communities as significantly, although disinfectant type had been reported previously to affect the structure of suspended communities in the DWDS ecosystem (Hwang et al, 2012b;Wang et al, 2014). A plausible explanation for this observation is that the biofilms in DWDS, because of the long-term community assemblage discussed above and reduced disinfectant penetration yielded by the polymeric biofilm matrix (Chen and Stewart, 1996), are likely resistant to certain perturbations.…”

“…Owing to a robust water treatment process, the product water supplied into the DWDS generally maintained stable water chemistry (Hwang et al, 2012b). Water quality monitoring across multiple sites in the distribution system also showed stable pH and turbidity (Table 2).…”

“…To maintain water quality integrity in the DWDS, the water utility applies residual disinfectants in accordance with compliance standards. The water treatment processes were described in detail previously (Hwang et al, 2012b).…”

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

“…However, a remarkably high abundance of candidate phyla was discovered in the present study. Candidate phyla and difficult-to-classify sequences were already observed previously in some chlorinated drinking water systems in high and low abundances (Eichler et al, 2006;Henne et al, 2012a;Hong et al, 2010;Revetta et al, 2010;Hwang et al, 2012). Nevertheless, up to now different methodologies with variations in their sensitivity have been used to study the microbial community composition of drinking water.…”

Using Amplicon Sequencing To Characterize and Monitor Bacterial Diversity in Drinking Water Distribution Systems

“…Metagenomics has been successfully used to investigate bacterial communities present in end-use tap water, experimental drinking water systems, and bacterial biofilms within pipes (6)(7)(8)(9)(10). However, very few studies have explored bacterial communities throughout full-scale DWDSs or investigated community variations between different systems.…”