Author ORCID Identifier

https://orcid.org/0009-0009-7676-8829

Semester

Spring

Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Emily Garner

Committee Member

Lian-Shin Lin

Committee Member

Kevin Orner

Abstract

Bacteria can survive treatment and enter drinking water distribution systems (DWDSs), or enter DWDSs through intrusion or maintenance work on the system. DWDSs can also be suitable environments for bacterial regrowth. Many factors can affect the microbial community composition of DWDSs, including various spatiotemporal, hydraulic, and water quality parameters. Although most bacteria within DWDSs are harmless, opportunistic pathogens, such as Legionella pneumophila, Pseudomonas aeruginosa, and Mycobacterium avium, can inhabit DWDSs and premise plumbing and are the leading cause of waterborne disease outbreaks in developed countries. Previous studies have attempted to establish relationships between various parameters and microbial growth, but the effects of spatial and temporal trends on particle-associated microbial communities in chlorinated DWDSs remain poorly understood. The objectives of this study were to 1) examine the microbial community composition within a full-scale chlorinated DWDS, 2) explore relationships between microbial community and various spatiotemporal, hydraulic, and water quality parameters, 3) investigate how sediment may be a driver of these relationships by examining both particle-associated bacteria (PAB) and total bacteria (TB), and 4) assess potential human health implications of bacteria within the DWDS. Bulk water samples were collected from the treatment plant effluent, a storage tank, and 12 other sites in a rural chlorinated DWDS at varying distances from the treatment plant on four sampling dates spanning six months. Microbial analyses were separated into TB and PAB for each sample, and amplicon sequencing targeting the 16S rRNA gene was performed to characterize the microbial community. Gammaproteobacteria dominated the DWDS and hydraulic parameters were drivers of differences in microbial communities between sites. This indicates that hydraulic changes led to the detachment of biofilms and loose deposits, subsequently affecting the microbial community composition at each site. Spatial variations in microbial community were stronger than temporal variations, differing from similar studies and indicating that the highly varied hydraulic conditions within this system may intensify spatial variations. Genera containing pathogenic species were detected, with Legionella and Pseudomonas detected at every site at least once and Mycobacterium detected at most sites. However, only one sample had quantifiable P. aeruginosa through quantitative polymerase chain reaction (qPCR), and no samples had quantifiable L. pneumophila or M. avium, indicating a low human health risk. This study establishes spatial variations in PAB associated with varied hydraulic conditions as an important factor driving microbial community within a chlorinated DWDS.

Embargo Reason

Publication Pending

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