In the wake of the Flint, Michigan water crisis, the scale and dangers of lead contamination in America’s aging water infrastructure have been exposed to the mainstream. Now, a promising new technique for identifying these hazardous pipes without the need for costly and disruptive excavation has been developed by a team of researchers at Drexel University.’
The patented method, pioneered by Ivan Bartoli, PhD, professor of civil, architectural and environmental engineering; Charles Haas, PhD, LD Betz Professor of Environmental Engineering; and Kurt Sjoblom, PhD, owner of Seaflower LLC, uses sound waves to determine the material composition of water pipes buried underground. By striking an accessible portion of the pipe, such as the curb stop valve, and analyzing the way the resulting stress waves propagate through the pipe and surrounding soil, the researchers can distinguish between lead, copper, steel and plastic pipes with a high degree of accuracy.
Lead poisoning can cause a range of serious symptoms, from irritability and fatigue to seizures and organ damage. Even low levels of exposure can interfere with children’s brain development, leading to learning and behavioral problems.
“Lead pipes, which are common in older cities, can leach lead into drinking water, posing serious health risk,” explained Haas. “No level of exposure is safe, and removing lead pipes is an urgent need.”
Despite the well-known dangers of lead, many cities have struggled to address the problem of lead service lines due to the high costs and logistical challenges of identifying and replacing them. In cities with older infrastructure like Philadelphia, Boston, and Washington, D.C., inconsistent record keeping may make locations of lead pipes a mystery, highlighting the need for the Drexel-led technique.
“Since visual line inspection or water sampling are the current methods for line material testing, the former is time and effort consuming, and the latter is costly and unreliable,” said Bartoli. “There is a current need to rapidly and cost-effectively identify the service line material supplying water to homeowners and residents in urban areas.”
The Drexel team’s acoustic method offers a promising solution. When a pipe is struck, stress waves are generated and travel along the length of the pipe. The speed at which these waves propagate depends on the pipe’s material properties. By measuring the time it takes for the waves to reach a series of sensors placed along the pipe, the researchers can calculate the wave velocity and generate a dispersion curve — a graphical representation of how the velocity varies with frequency.
The team’s research progressed in stages, starting with laboratory tests on exposed pipes filled with water. They then moved on to testing pipes buried in sand, and finally, in real soil conditions. To collect the necessary data in the field, the researchers use a portable setup consisting of an instrumented hammer to strike the pipe and an array of highly sensitive accelerometers to detect the resulting vibrations. The signals from these sensors are then processed using advanced signal processing algorithms and machine learning models to extract the key features that distinguish each pipe material.
To validate their new method, the researchers partnered with several water utilities to field test the technology in real-world conditions. The results have been promising, with a success rate of around 80% in identifying non-lead pipes and 70% in identifying lead pipes specifically.
“Based on the feedback from water utility companies, my understanding is that if we can get to 85% certainty in determining that a pipe contains lead, that would be very useful for them,” added Bartoli. “We are continuing to evolve our approach, and further patent applications may be forthcoming,” added Haas.
Haas shared the team’s plans for further testing and commercialization: “In the US, we have re-engaged with the Philadelphia Water Department and will do more testing for them over the coming months. We’ve also worked with the Wrightsville Municipal Authority in York County, PA, to confirm their records of lead pipe locations.”
In the UK, we are working on the logistics for testing at a facility with buried pipes of known materials, which they will treat as a blind test for us before moving forward. We’re looking forward to the challenge.”
The implications of this research are significant. With new EPA regulations mandating the replacement of all lead service lines in the coming years and billions of dollars in federal infrastructure funding available to support this effort, water utilities are in urgent need of better tools to locate and prioritize lead pipe replacements. The Drexel team’s patented acoustic pipe identification method represents a major step forward in this fight against lead contamination in drinking water, promising to help secure safer, healthier water for communities across the country and beyond.
