Semester

Spring

Date of Graduation

2022

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Civil and Environmental Engineering

Committee Chair

Emily Garner

Committee Co-Chair

Lian-Shin Lin

Committee Member

Kevin Orner

Abstract

Drinking water distribution systems (DWDS) are critical for protecting public health by ensuring safe water is transported from centralized treatment facilities to consumers. Sediment accumulation in DWDS is a common challenge that water utilities face that may pose some health risks when waterborne pathogens colonize biofilms formed on the sediment surface. Water utilities often establish flushing routines to help mitigate sediment accumulation in their system but the role that sediment plays in contributing to the total microbial loading in the system is unclear. The main objective of this study was to determine if sediment in a DWDS presents a significant source of microbial loading. In addition, changes to sediment and microbial loading that occur with duration after a flushing event were monitored. The influence of other physicochemical parameters on sediment and microbial loading was also investigated.

Water samples were collected at 14 different sites in the Preston County Public Service District #1 DWDS located in Arthurdale, WV. Samples were collected at each site once before and at three time points after routine flushing was performed. Total bacteria and sediment associated bacteria were quantified in all samples via quantitative polymerase chain reaction targeting the universal bacterial 16S rRNA gene. Samples were also tested for various physiochemical parameters such as chlorine, pH, conductivity, temperature, turbidity, total suspended solids, heterotrophic plate count, total organic carbon, iron, manganese, and magnesium.

It was found that sediment associated bacteria can be a significant source of microbial loading in distribution systems, with up to 4 log 16S rRNA gene copies per mL detected on sediment in DWDS samples. However, sediment loading alone was not a strong predictor of high sediment associated bacterial loading in these samples. On two sampling dates, chlorine concentration was negatively correlated with sediment associated bacteria, indicating that maintaining a chlorine residual is important for controlling growth.

These findings help to establish sediment as an important conduit for microbial loading in a DWDS. Since biofilms formed on the surface of sediment can be a possible environment for harmful pathogens, this information is important for water utilities to consider to ensure the best water quality to their consumer.

Embargo Reason

Publication Pending

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