Oct. 17, 2013
An article by Courtney Mitchell, published in the Oct. 15 University Gazette, describes the Compartment Bag Test, developed by Kenan Distinguished Professor Mark Sobsey, PhD, to test the safety of drinking water in low-resource areas. The article is reprinted here with permission.
According 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.”