Type of Document Master's Thesis Author Rushing, Jason Clark URN etd-07292002-124850 Title Advancing the Understanding of Water Distribution System Corrosion: Effects of Chlorine and Aluminum on Copper Pitting, Temperature Gradients on Copper Corrosion, and Silica on Iron Release Degree Master of Science Department Environmental Engineering Advisory Committee
Advisor Name Title Edwards, Marc A. Committee Chair Novak, John T. Committee Member Vikesland, Peter J. Committee Member Keywords
- by-product release
Date of Defense 2002-07-24 Availability unrestricted 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.
Filename Size Approximate Download Time (Hours:Minutes:Seconds)
28.8 Modem 56K Modem ISDN (64 Kb) ISDN (128 Kb) Higher-speed Access RushingETD.pdf 1.61 Mb 00:07:27 00:03:49 00:03:21 00:01:40 00:00:08
If you have questions or technical problems, please Contact DLA.