Our nation is in need of sustainable potable water infrastructure because of the looming $183 billion of distribution water infrastructure that must be replaced in the U.S. during the next two decades. Recently approved standards for polyethylene materials in potable water public infrastructure indicate that polyethylene pipes are increasingly being installed for water distribution and plumbing worldwide, although the agents and mechanisms responsible for their physical failure caused by long-term chlorinated water exposure are unknown. Further, contaminant interaction of aged polyethylene has received little scrutiny. Under this award, an interdisciplinary research team will integrate chemistry and engineering to examine the mechanisms that control new and aged high-density polyethylene (HDPE) resin and HDPE water pipe degradation as well as aged polyethylene contaminant interaction. An outreach component will integrate teaching of radical chemistry and polyethylene infrastructure engineering to middle school students through a summer camp at the Science Museum of Southwest Virginia and to high school students in the Montgomery County, VA Public School System.

Project Report

PIs: Dr. Andrea M. Dietrich Dr. James. M. Tanko Civil and Environmental Engineering Chemistry Virginia Tech Virginia Tech Our National Science Foundation research project provided the opportunity to train and educate the next generation of chemists and engineers, including: many middle school students who attended a "Think Radically" summer camp, 1 high school student and 4 undergraduate students who worked during the summer, 2 undergraduates who worked during the school year, and 4 graduate students. In addition to learning about drinking water, polyethylene pipes, and chemistry, the students were able to present their research at conferences and publish their results in technical journals. This work is notable because environmental engineers and chemists worked collaboratively to address a potable water problem facing many in society - including homeowners, plumbers, the drinking water industry and plastic pipe manufacturers: how do polyethylene water pipes perform in disinfected drinking water? Water is critical for life, and water infrastructure (including pipes) are necessary to delivering drinking water to consumers. Polyethylene pipes are increasingly used in water mains and premise plumbing to deliver water to consumers. Virginia Tech researchers Andrea Dietrich, Jim Tanko and their students demonstrated that the polyethylene surface ages faster when exposed to aqueous disinfectants and oxidants in water. When exposed to organic chemicals, including solvents and gasoline components, new and chlorine-exposed polyethylene pipes absorb the chemicals and become contaminated. The properties of organic chemicals are more important than the properties of the polyethylene for predicting contamination, with chemicals that are poorly soluble in water more likely to penetrate the polyethylene pipe. To be sustainable, polyethylene pipes need long life times, to be leak-free, and resistant to degradation and contamination during normal use. Our research demonstrated that chlorine disinfectants and oxygen in drinking water are capable of inducing chemical changes to the surface of the polyethylene material that may lead to shorter service times for the pipes.

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