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Researchers Test Water Safety Tests

Wisconsin State Journal :: LOCAL :: D4
Sunday, August 26, 2007
David Wahlberg

Whether health officials learn that drinking water has been contaminated could depend on what test they use to detect fecal bacteria, a new study by researchers at the Wisconsin State Laboratory of Hygiene suggests.

The U.S. Environmental Protection Agency has approved 10 tests to detect total coliform and E.coli, bacteria that can indicate the presence of pathogens in water. Water utility managers often question which test they should use.

Scientists at the state lab applied the 10 tests to water samples from northern, central and southern Wisconsin, to which five kinds of bacteria had been added. The researchers also checked how well the tests suppressed a different kind of bacteria that can lead to "false positives" for the bacteria labs want to look for.

Most tests performed well. But some didn't detect some of the five bacteria, and one test didn't detect most bacteria added to the central Wisconsin water. That water was more acidic, which may interfere with test performance.

Another test didn't suppress the "false positive" bacteria in the water samples from all three parts of the state.
The tests can have major consequences, as positive readings can lead health officials to advise residents to boil water until it is disinfected.

More research is needed before some tests are recommended over others. But the findings could help water utility managers decide which test to use, said microbiologist Jeremy Olstadt, lead author of the study.

The study, also involving researchers James Jay Schauer, Jon Standridge and Sharon Kluender, was published in the July issue of the Journal of Water and Health.

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