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University Gazette

The University of North Carolina at Chapel Hill

Sobsey’s simpler water test is ‘a driver for change’

sobsey_mark_450According to a 2012 UNC study, 1.8 billion people around the world use unsafe water.

But a test from the lab of Mark Sobsey in the Gillings School of Global Public Health is helping to combat the problem by making water testing simpler and more accessible to the low-resource areas that need it most.

The Compartment Bag Test (CBT) is performed with a container similar to a sandwich bag and can be done anywhere, without access to a laboratory, special equipment, or even electricity. It uses the same testing principles that have been used commonly for years, but its portability, affordability and simplicity makes water testing accessible to nearly anyone.

“Those of us who worked in developing countries saw the substantial need for a low-cost test for microbial water-quality analysis,” said Sobsey, Distinguished Kenan Professor of Environmental Sciences and Engineering. “I started to wonder if I could do this in a plastic bag.”

The CBT, which Sobsey and a graduate student developed in 2007, has just a handful of parts: a 100-milliliter bottle to collect the water sample, a single-serving bag of bacterial medium to grow the bacteria of interest, a small plastic bag divided into five internal compartments and a plastic clip to seal off the bag.

The test serves the same purpose as tried-and-true test tubes, but without the hassle of the tubes and their caps, the pipettes, the racks or the autoclave needed for sterilization. The bag’s compartments and the sealing clip keep the individual samples from cross-contaminating, and the last step, incubation, takes just 24 hours.

Samples that remain the yellow-brown color of the water mixed with bacterial medium are negative for contamination. If the water turns blue or blue-green, it’s contaminated. How many of the five sections turn positive or negative determines the safety of the water.

“Many have asked why we need another test, when the ones we have work fine. In developing countries and other low-resource areas, they might not have labs, and it’s hard to take pipettes, culture tubes and tube racks into the field,”

Sobsey said. “This compartment bag system makes testing convenient so more people can know what they are drinking and do something about it.”

‘A driver for change’ worldwide

In 2010, Sobsey was invited to share his research at the inaugural LAUNCH event, a NASA initiative that identifies and supports 10 innovators who are working on solutions to the world’s problems.

Shortly after, the U.S. Agency for International Development piloted the CBTs, matching them against standard tests in a demographic health survey in Peru where the CBT was used in 665 households. The summer of 2013, the agency took CBTs to Liberia. In both countries, the CBTs returned results as accurate as standard testing.

The tests have now been used in more than two dozen countries. Alice Wang, a doctoral student in Sobsey’s lab, recently took them into 50 homes in Tanzania where she tested for contamination and surveyed the families on how they felt about their water.

“In virtually all of these places,” Sobsey said, “it’s been a driver for change.”

As Sobsey and his students realized there was demand for the product – from other countries, academic colleagues and agencies – they founded Aquagenx, a company that now makes the CBT available commercially ( They have developed instructions and outreach materials on how to treat contaminated water with common steps such as boiling, chlorination and pasteurization in the sunlight.

“In many developing countries, where people are gathering water and bringing it home, the water might not come from a clean source to begin with,” Sobsey said. “Their fingers might have harmful bacteria because of poor hygiene, and they touch the water dipping a cup into the container.”

There are many possible paths to contamination that can make people very sick, he said, and the next step is action.

“Whoever is responsive for that water, whether it’s in the government or at the household level, if they find bad water, then the outcome should be to investigate why it’s contaminated and take immediate measures to make the water safe,” Sobsey said.

While the portability and affordability of the tests makes them well suited for lower-resource areas, Sobsey said developed countries would find them useful in times of crisis.

“Something like this could have been employed immediately after Hurricane Katrina to more quickly determine if the water was safe to drink, have in the house or even walk through,” he said. “Official testing took much longer to put in place. If we were to see a disaster like this again, you could take this test right to the water, test and let people know overnight.”

Water_in_Our_World_graphic_NB300Working global to local

Sobsey’s work spans from global to local communities, because he is passionate that everyone should have access to clean water, no matter where they live.

Surveys show that about one in every six people in North Carolina is responsible for his or her own water. Sobsey is one of them. His home, outside the city limits of Chapel Hill, is served by well water.

“Most consumers will say that they think their water is safe, or they don’t know. You can pay the county to test it, but that costs money so people do this rarely or never,” Sobsey said. “But your septic waste system could fail and that failure could be hidden.”

With easy access to the CBT, people can test their water whenever necessary.

Cities, towns, counties and individuals across the state have for years contacted Sobsey’s lab and asked for help determining the safety of their water supplies. Sometimes it’s because they want to make sure they are in line with state regulations on microbes in reclaimed water. Other times, it’s in an emergency.

“We’re periodically called out to investigate suspected water-borne outbreaks or contamination in a city water supply. Often a town has chronic problems and they can’t figure it out,” Sobsey said.

Such requests allow the scientist and his students to serve the state, particularly underserved communities and rural households. It’s also an opportunity for valuable research for his graduate students, who like Sobsey, are eager to solve water issues.

“When I was starting out, there was little known about the risks of viruses in water,” he said. “The methods of testing were so poorly developed that there was a clear opportunity for me to make a difference.”

After 39 years at the Gillings School and continued breakthroughs in his research, Sobsey looks forward to making even more of an impact, especially in developing countries where simple solutions could save lives.

“In places where people’s needs are largely unmet, we have to bring simple water-quality testing,” he said. “We need to bring them tools for water-quality analysis, and the tools to treat water, so that everyone has access to safe water – and everyone knows that their water is safe.”