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dc.contributor.authorRushing, Jason Clarken_US
dc.description.abstractWhen severe copper pitting problems impacted customers at a large utility, studies were begun to attempt to diagnose the problem and identify potential solutions. A series of tests were conducted to characterize the nature of pitting. Desktop comparisons of pinhole leak frequency and treatment practices at nearly utilities were also documented to identify treatment factors that might be influencing the initiation and propagation of leaks.

Factors identified included the presence of relatively high levels of free chlorine and aluminum in the distribution system. Experiments were conducted to examine the effect of these constituents on copper pitting under stagnant and flow conditions. That led to discovery of a synergistic redox reaction between chlorine, aluminum solids, and copper metal as evidenced by increased chlorine decay rates, non-uniform corrosion, and rising corrosion potentials.

Temperature changes had been suspected to increase copper pitting frequency and copper release to drinking water. Experiments examined the effect of temperature gradients on copper pipe corrosion during stagnant conditions. The pipe orientation in relation to the temperature gradient determined whether convective mixing would occur, which influenced temperature gradients within the pipe. This work is the first to demonstrate that temperature gradients lead to thermogalvanic currents, influences copper leaching and scale type.

Iron release from corroding water mains is another concern of many water utilities, but little is known about chemistry factors that influence the problem. In laboratory experiments, higher levels of silica caused more iron release to the water and decreased the size of suspended iron particles. Silica levels also changed during the experiment: it decreased through incorporation into a dense scale, and increased by release from cast iron during corrosion. Silica slightly decreased iron corrosion rates near the end of this 6-month test.

dc.publisherVirginia Techen_US
dc.rightsI hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Virginia Tech or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report.en_US
dc.subjectby-product releaseen_US
dc.titleAdvancing the Understanding of Water Distribution System Corrosion: Effects of Chlorine and Aluminum on Copper Pitting, Temperature Gradients on Copper Corrosion, and Silica on Iron Releaseen_US
dc.contributor.departmentEnvironmental Engineeringen_US
dc.description.degreeMaster of Scienceen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineEnvironmental Planningen_US
dc.contributor.committeechairEdwards, Marc A.en_US
dc.contributor.committeememberNovak, John T.en_US
dc.contributor.committeememberVikesland, Peter J.en_US

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