Photo by @hupdiggs.

Community Contributor | Dan Lane, UNC Chapel Hill


If you are reading this article, you are probably one of the fortunate ones. Chances are you can trust that the glass of water in front of you is safe to drink. Sadly, that’s not the case for about a quarter of the world’s population. Nearly two billion people around the world get sick every year from untreated water. Of those affected, nearly two million die, including 750,000 children.

Simply put, contaminated water leads to more deaths than HIV/AIDS.

The silent assassins are bacteria like E. coli, which find their way from fecal waste into the local water supply. You can’t see it, smell it, or taste it, but it can kill you. Water may be a source of life, but it is also a vessel of disease and death. Ideally, everyone would have access to safe, treated water. But building that kind of infrastructure — especially in remote areas — takes time and money, something many governments and nongovernment organizations (NGOs) lack. In the meantime, the best strategy for reducing the risk of contracting water-borne illnesses is to determine where the bacterial bad guys are lurking.

More people die every year from contaminated water than HIV/AIDS. Photo courtesy, Dr. Mark Sobsey.
Fecal bacteria, like E. coli, infect nearly 2 billion people per year.  Photo courtesy Dr. Mark Sobsey.

The problem is that most detection methods are prohibitively expensive and technical, and getting the results takes a long time. Many tests require taking specialized gear — test tubes, pipettes, and sterilizing equipment — to the water source. Another option is to ship water samples from the field to commercial labs around the world. Both methods require trained technicians and can push the price up to $100 per test. Such high costs have severely limited the number of water-quality tests being conducted in at-risk regions — until now.

Enter Dr. Mark Sobsey, a professor of public health at the University of North Carolina-Chapel Hill. Sobsey developed a cheap and simple test to determine how many E. coli bacteria live in a given water sample. His Compartment Bag Test (CBT), which looks like a plastic reclosable bag with five internal compartments, doesn’t require fancy lab equipment or trained technicians. It’s designed to be used by anyone anywhere.

The self-contained kit reveals within a day if a water source is safe to drink. Here’s how it works:

1. Fill a vial with water.

2. Add some bacterial medium (bacteria food made up of carbon compounds, digested proteins, and salts).

3. Pour the water sample into the CBT.

4. Let the bag sit overnight.

The CBT costs less than $10, compared to $100 for alternative testing kits. Photo by @hupdiggs.

Compartments containing at least one E. coli cell turn bluish green. Depending on which compartments change color, you can determine the level of contamination in the water sample. For example, if only the smallest compartment turns green, the water has about one E. coli cell in every 100 milliliters. That’s “probably safe” to drink according to Sobsey. If all five compartments turn green, your water is “unsafe,” which means you definitely don’t want to drink it.

No technician required: the CBT allows end users to determine if their water is safe to drink. Photo courtesy Dr. Mark Sobsey.

At a cost of less than $10, Sobsey’s user-friendly kit is poised to revolutionize the breadth and scope of water-quality testing. For example, a 2012 United Nations report concluded it was not possible to measure water quality worldwide, in part because of money. Instead of measuring quality, the UN set its standards based on whether water is “improved.” However, “improved” water includes any water run through a pipe. Channeling muddy puddle water through a lead pipe could be considered “improved” by the UN.

“As far as measuring what water is safe to drink, [the UN] probably got it wrong,” says Sobsey.

The cheaper tests allow NGOs to expand their water-quality testing. Through his company, Aquagenx, which he calls his “socially responsible LLC,” Sobsey has sold 20,000 CBTs to aid organizations around the world, such as USAID.

“We should be responsible to bring testing capacity to the people that need it,” says Sobsey. “Everybody deserves to know if their water is safe.”


To Drink, or Not To Drink 6 August,2013Daniel Lane


Daniel Lane

Daniel Lane is a science writer and graduate student at UNC Chapel Hill. After relocating from Rochester, NY, Daniel has covered science issues affecting North Carolina's environment and communities. When he is not writing about science, Daniel enjoys going to garage sales (for the books, of course!) and running around his adopted home of Chapel Hill.

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