Blacksburg, VA -- Many factors influence the quality of drinking water, and a relatively new problem is causing concern. The corrosion of metallic plumbing materials, once thought to last for centuries, is producing some extraordinary costs and environmental problems to consumers and to industry.
The American Water Works Association (AWWA) estimates that it will cost U.S. water utilities $325 billion during the next 20 years to replace losses due to corrosion and the need to upgrade water distribution systems. Nationally, corrosion of metals is believed to consume 4 percent of the gross domestic product.
Despite these costs, surprisingly little research has been conducted in this area. One of the pioneers is Marc Edwards, recipient of the National Science Foundation Presidential Fellowship for his work in environmental engineering. Edwards points to some relatively new water treatment steps that remove natural organic inhibitors of copper corrosion as a cause for this deterioration.
The environmental impacts from the deteriorated plumbing include holes in pipes formed through corrosion, which allow contaminants into drinking water systems, the loss of the water resource itself, and cause property damage. More recently, leaching of lead and copper from plumbing materials into drinking water has received widespread attention due to health concerns, and forthcoming regulations will severely limit the quantities of corrosion by-products that appear in sewage discharge and sludge.
"The proposed regulations are difficult to meet," Edwards, an associate professor of civil and environmental engineering at Virginia Tech, says. "For example, consideration of the proposed limits on copper have prompted serious discussion of banning its use in the future as a plumbing material and possible replumbing of existing homes in some cases. This decision does not seem practical, since it would cost each homeowner several thousand dollars, and copper has many important benefits as a plumbing material when compared to proposed alternatives."
Edwards' research is aimed at gaining a better understanding of how to mitigate excessive corrosion problems and the associated release of metals to water. "Preliminary experiments illustrate that a wide range of factors are involved, including natural organic matter (NOM), pH, alkalinity, sulfides and other dissolved materials in water," he reports. "In some cases, particularly bad combinations of these components can cause a new copper pipe to leak in as little as two weeks, compared to the normally expected pipe lifetimes of hundreds or thousands of years."
His work is leading to the ability to predict water qualities that are susceptible to problems and to the development of specific steps that may mitigate problems when they occur. In fact, Edwards has developed a software program to help guide utilities when considering options for corrosion control.
The Virginia Tech researcher has also developed some innovative corrosion testing techniques. Conventional corrosion testing is time consuming and expensive since it requires months or years of exposure before reliable results are obtained. Edwards designed a test that circumvents some of these limitations. By apply a corrosion accelerating current to the metal, he can force a rapid aging process to take place, producing pipe samples in five days that are similar to those obtained after months or years of conventional testing. In some cases, results can be obtained at a fraction of conventional test costs.
Edwards has built much of his reputation as a researcher in the area of corrosion, and he now devotes about half of his time to this endeavor and the other half to conventional studies of drinking water treatment. At present, only a handful of academics in the U.S. are working on the drinking water corrosion issue, which requires expertise in materials, water chemistry and microbiology.
As an engineer, Edwards is attempting to merge the science with the technology to help water utilities, plumbers, homeowners, and pipe manufacturers obtain practical solutions to this costly problem. "I believe that our corrosion research at Virginia Tech will significantly advance the breadth and practical application of environmental engineering," he says.
Balancing science and technology is a natural choice for Edwards. As an undergraduate, he earned his degree in biophysics from the University of Buffalo. While he contemplated potential careers in veterinary medicine and geophysics, Edwards also decided to apply to four environmental engineering graduate schools. After a visit, he ultimately accepted a fellowship at the University of Washington at Seattle. While he was in graduate school, he and his advisor Mark Benjamin patented a new process for treating metal bearing waste waters, which to date has received more than $2 1/2 million in research and commercialization funding.
Edwards' current research on corrosion, funded by both private and public interests, exceeds $600,000, and is helping to support four doctoral candidates and five master's students at the University of Colorado and Virginia Tech. Since 1992, students in Edwards' group have won 12 nationally recognized awards for undergraduate and graduate research in environmental engineering.
The above story is based on materials provided by Virginia Tech. Note: Materials may be edited for content and length.
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