Electronic Theses and Dissertations

Date

2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Civil Engineering

Committee Chair

Maryam Salehi

Committee Member

Charles Camp

Committee Member

Claudio Meier

Committee Member

Maryam Salehi

Committee Member

Paul J Palazolo

Committee Member

Shawn Brown

Abstract

The chemical and microbiological quality of water can deteriorate as it is conveyed through plumbing materials into and within buildings, posing significant public health risks. Potable water plumbing systems have the potential to release heavy metals and promote microbial growth in tap water. Prolonged water stagnation within building plumbing creates a reductive environment, which promotes the release of heavy metals from corroded, metallic potable water plumbing fixtures into the potable water. While the increased installation of plastic potable water pipes was intended to address corrosion issues associated with metallic pipes, plastic pipes are also susceptible to degradation and microbial growth. These processes can affect their heavy metal transport characteristics and consequently impact the safety of tap water. Thus, in this dissertation, water chemistry, polymer sciences, surface science, and environmental engineering principles were applied to address several knowledge gaps regarding the physical and chemical processes that affect heavy metal release from metallic and plastic potable water pipes. The first chapter presents an overview of the research background, identifies knowledge gaps, and outlines the structure of the dissertation. The second chapter focuses on the impacts of non-routine extended school closure (due to the unprecedented COVID-19 pandemic) on heavy metals release into the tap water. Moreover, the potential sources of Pb release into schools' tap water were identified, and an effective remediation plan was developed. This investigation found that lead-containing fixtures, connecting plumbing, and interior plumbing are sources contributing to lead release into the water at the studied schools. The third chapter explored how biofilm and water pH influence the lead release from crosslinked polyethylene-A (PEX-A) and high-density polyethylene (HDPE) drinking water pipes, compared to copper pipes under both flowing and stagnant conditions. At a lower water pH of 5.0, the release of Pb from plastic pipes into the contact water increased compared to pH vi 6.0 and 7.8. The release kinetic experiments revealed that at pH 5.0, the presence of biofilm resulted in a significant increase in lead release from plastic and copper pipes under flowing conditions compared to stagnant conditions. The fourth chapter examined the effects of accelerated chemical aging on surface morphology and chemistry of PEX-A pipes and evaluated its impact on the release of heavy metals (Pb, Cu, and Zn) from metal-accumulated pipes. Additionally, the impact of aging on the chlorine decay behavior of PEX-A pipes was studied under different water temperatures. The surface chemistry analysis revealed the formation of several oxidized carbon functional groups on the pipe’s surface after accelerated aging. The metal release experiment showed that, at pH 6.0, the new pipe released greater levels of Pb, Cu, and Zn compared to the aged pipes over 5 days of contacting metal-free water. Moreover, a significant reduction in total chlorine residual concentration was found in both new and aged pipes when exposed to hot water (T= 50 °C) compared to water at room temperature. Aged pipes showed a significant reduction in total chlorine residual concentration, with a higher rate of chlorine decay observed in aged pipes compared to new ones. The fifth chapter concludes the dissertation and offers recommendations for future research in relevant areas.

Comments

Data is provided by the student.

Library Comment

Dissertation or thesis originally submitted to ProQuest.

Notes

Embargoed until 11-04-2026

Download

Available for download on Wednesday, November 04, 2026

Share

COinS