Dec. 30, 2013


Dr. Mark Sobsey, with the compartment bag test (CBT) he helped develop. Photo by Dan Sears.

A simple water quality test that detects the presence of E. coli is a runner-up winner of the United States Agency for International Development (USAID) Science and Technology Pioneers Prize.  

One of the developers of the device, the compartment bag test (CBT), is Mark Sobsey, PhD, Kenan Distinguished Professor of environmental sciences and engineering at the University of North Carolina at Chapel Hill’s Gillings School of Global Public Health. Sobsey and three colleagues founded the social enterprise Aquagenx through a business incubation program at UNC to produce and market the test kits.

Offered for the first time this year by the USAID Office of Science and Technology, the Pioneer prize recognizes excellence in the use of science and technology to solve development challenges.

The portable, self-contained CBT detects E. coli, which can be deadly to young children and the elderly. When found in water, these intestinal bacteria indicate the source is contaminated by sewage or animal waste, signaling an alert that other disease-causing organisms may be also lurking.

Laboratory tests for E. coli require electricity, refrigeration, refrigerated transport, and trained technicians. The CBT alternative offers accurate, onsite testing that can be done by anyone.

The test kit is a plastic bag that will hold a 100-ml sample of water in five separate compartments – each a different size. The sample is mixed with a bacterial culture, then poured into the bag, sealed and left overnight. The presence of E. coli manifests by turning the water blue. The number of blue compartments and the darker the color indicate the density of the E. coli contamination in the water source.

“It’s much more convenient than a laboratory test,” said Sobsey, who was the leader of this particular USAID’s MEASURE Evaluation project. “The best thing is it can be conducted by the surveyors onsite.”

The CBT was tested in Peru with USAID’s door-to-door Demographic and Health Surveys, which have been gathering critical information for development since 1984. If a household water supply shows the presence of E. coli, the surveyors explain how to purify the water and leave behind literature to remind household members to either strain their drinking water through tightly woven fabric, boil it, or stand it in a clear plastic container in the sun for 24 hours, all of which are enough to kill the potentially deadly bacteria.


Gillings School of Global Public Health contact: David Pesci, director of communications, (919) 962-2600 or

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