The Environmental Protection Agency (EPA) wants water utilities to know right away when a dangerous chemical has been dumped in the water supply. But early warning technologies are difficult to come by when it comes to water.

“Many methodologies can detect chemicals in water,” says Tim Oppelt, director of the EPA's National Homeland Security Research Center. “The trouble is that you need a detector for each chemical. And if the chemical in the water isn't the one you are trying to detect, you won't find it.”

Fears about terrorist attacks on the water supply make it important to overcome this problem. Recently, the EPA and Battelle, a Cincinnati-based science and technology consultant, tested a new technological approach to rapid detection of water supply contaminants.

Conducted under the EPA's Environmental Technology Verification (ETV) program, the experiment tested the application of rapid toxicity monitoring and testing systems to drinking water.

These systems have been around for years and have proven useful in monitoring wastewater effluents discharged by industrial facilities. “Our goal in the Battelle test was to see how well these kinds of technologies will work to detect contaminants that might be intentionally introduced into drinking water systems,” Oppelt says.

Rapid testing systems are composed of living organisms, such as algae or water fleas. Called bioassays, they indicate the presence of low levels of toxic chemicals by changing the way they emit light, altering the rate at which they metabolize nutrients, or by undergoing some other detectable biological transformation.

The Battelle tests evaluated eight bioassays formulated by seven different companies. Each bioassay was tested in water containing each of five classes of potential contaminants: industrial chemicals, pesticides, drugs, nerve agents and biologically-produced chemical toxins. Nine chemicals from these categories underwent testing.

None of the tests examined microbes or biological contaminants. Other detection schemes will have to look for those kinds of problems.

Before the tests, researchers removed the chlorine and other chemicals that commonly occur in drinking water. “These chemicals cause some of the organisms and enzymes we were testing to burp,” Oppelt says. “We removed them from the initial tests to avoid false positives.”

The test results were mixed, according to Oppelt. Most of the bioassays showed sensitivity to only a few of the toxic chemicals in the test. The goal was to find at least one that reacted to all nine chemicals.

One did. Unfortunately, this bioassay also reacted to a host of non-toxic chemicals. After the primary test, researchers re-added chlorine, aluminum, copper, iron and manganese to the test water and discovered that the ultra-sensitive bioassay also reacted to each of those.

“I think bioassays will eventually work,” Oppelt says. “But at this point, there is no silver bullet out there. For now, we advise water utilities considering these kinds of technologies to look at the test results at our Web site. Before using any of these technologies, the utility would need to fully characterize the performance of that technology using a range of samples representative of the water qualities in its district.”

Oppelt also says that any final solution to the rapid detection problem will likely include a combination of sensing technologies including bioassays and more conventional chemical sensors all tailored to the characteristics of individual water supplies. An effective bioassay will indicate the presence of something that needs looking into. But it won't replace qualified hand sampling and further testing.

What happens when a utility detects a toxic attack on its water system? Does the EPA recommend decontamination technologies? “This is an area that needs a lot of work,” Oppelt says. “Right now, there isn't a lot of good information, especially in the area of microbials that might get into the distribution system. Typically, though, you would shut the system down and flush it or hit it with high levels of chlorine. But there is more that we need to know about toxic chemical contamination.”

The complete test results for the eight bioassays evaluated in the ETV tests appear on the EPA Web site at www.epa.gov/etv. Click on verified technologies and then go to rapid toxicity testing systems.