Semester

Spring

Date of Graduation

2025

Document Type

Thesis (Campus Access)

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Emily Garner

Committee Co-Chair

John Hando

Committee Member

John Hando

Committee Member

Kevin Orner

Abstract

Properly operated and maintained drinking water distribution system (DWDS) storage tanks play a crucial role in allocating safe drinking water to customers and upholding public health standards. However, varying operational processes and infrequent tank maintenance can result in water quality degradation through the loss of disinfectant residual, bacterial growth, and potential contamination. Low water turnover and stagnation within tanks contributes to elevated water age and disinfectant residual decay potentially altering microbial community composition in DWDSs. Storage tanks have been documented as survival areas for bacterial pathogens as well as hot spots for the formation of disinfection by-products (DBPs) in DWDSs. Sediments accumulate in low flow areas, like storage tanks, and have important implications for the presence of pathogens including Legionella spp., Mycobacterium spp., and Pseudomonas aeruginosa, posing potential public health risks. However, the chemical composition and microbial community associated with DWDS tank sediments remains poorly understood, largely due to difficulty accessing these samples. The objectives of this study were to 1) assess the relationship between DWDS storage tank physical, chemical, and hydraulic characteristics with microbial community composition in water and sediment in representative storage tanks within a chlorinated DWDS, 2) investigate the variation in water quality within individual tanks in relation to different collection depths, and 3) identify infrastructure and management characteristics that influence microorganisms and DBPs in drinking water tanks. Bulk water and sediment samples were collected through local utility collaboration from seven different storage tanks in a chlorinated DWDS. Bulk water samples were collected from each tank from varying depths (top, middle, and bottom) as well as DWDS locations prior to tank storage and after tank storage. Sediment samples were also collected from the bottom of each tank. Amplicon sequencing targeting the V4-V5 region of the 16S rRNA gene was conducted to characterize the microbial community. Alphaproteobacteria dominated DWDS water samples, whereas Gammaproteobacteria dominated sediment. Microbial community composition predominately varied based on tank site, aligning with previous studies highlighting spatial variability as a driver of microbial diversity in DWDSs. Distribution system characteristics and water quality parameters, particularly pipe miles from the treatment plant and total chlorine, also significantly influenced community structure at each tank site, reinforcing the role spatial differences have in shaping microbial communities in DWDS tanks. Genera containing pathogenic species including Stenotrophomonas and Pseudomonas were detected at least once at every site with detection of Acinetobacter at most sites. This study establishes a greater understanding of the microbial community within DWDS storage tanks and the impact that tank conditions and characteristics can have on distribution system water quality.

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