Date of Award

2022

Document Type

Open Access Dissertation

Degree Name

Doctor of Philosophy in Civil Engineering (PhD)

Administrative Home Department

Department of Civil, Environmental, and Geospatial Engineering

Advisor 1

Brian Barkdoll

Committee Member 1

David Watkins

Committee Member 2

Melanie Watkins

Committee Member 3

Robert Handler

Abstract

Since many water distribution systems (WDSs) experience saltwater intrusion, system behavior during saltwater intrusion is important. An alternative to the currently accepted WDS decontamination method of hydrant flushing is needed since during the current procedure all contaminated water is discharged to the surroundings which imposes environmental impacts. Hence, this research was conducted to study salt spread in different WDSs and to seek an alternative to hydrant flushing as a way of WDS decontamination. First, salt contamination was modelled in real water system models to document the salt spread. It was found that (1) if salt enters as a short pulse, it may contaminate different parts at different times; (2) in a multi-reservoir system if any reservoir remains fresh during a salt contamination event, contamination might take a longer time to reach the system edges; and (3) for all system types, time to clear the system from salt contamination is linearly correlated to the rate of salt entry at the source. Second, the performance of a containment pond was evaluated as an alternative to hydrant flushing, in which a pond lined with impermeable material will be constructed in a suitable place. Network modeling was performed, and it was found that (1) a containment pond can be a better option for WDS decontamination from an environmental viewpoint; (2) flushing only into the containment pond cannot clear all areas of the system; and (3) for some systems, some pond locations might be better from an economic perspective, while other locations will be better environmentally. A containment pond also has some environmental impact since the pond requires initial construction. Also, the decontamination time depends on the decontamination option chosen. Finally, a life cycle assessment study was performed using SimaPro for both the decontamination options and the impacts were assessed using IMPACT 2002+. The results show that (1) a containment pond can reduce the environmental impact caused during hydrant flushing alone; (2) using a containment pond can be more effective in an urban area; and (3) the time needed for the decontamination and the area exposed to contaminated water significantly affect environmental impact.

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