Scientists Seek Early Warning Of Drinking Water Threats

Civil Engineering Professor Greg Harrington is leading a two-year project to determine how well water-treatment technologies remove Cryptosporidium and other microorganisms before they reach the kitchen tap.

The $250,000 project is funded by the U.S. Environmental Protection Agency and the American Water Works Association Research Foundation, an international nonprofit group devoted to drinking-water quality. Joining Harrington in the project will be Jon Standridge and David Battigelli, scientists at the Wisconsin State Laboratory of Hygiene.

"If we review waterborne outbreaks of infectious disease in the United States, we find that the culprit was identified in only about half the cases," says Harrington. "There are numerous microorganisms, but detection methods are available for only a small fraction."

This project will focus on a half-dozen pathogens of future concern as a health threat in drinking water, he said. After growing pathogens in the lab, the researchers will add the pathogen-spiked "cocktails" to pilot-scale drinking water treatment systems. The approach will help them evaluate the ability of different treatment techniques to remove the bugs.

The two pathogens of greatest concern since 1980 have been Giardia and Cryptosporidium, and both have caused major health threats in the United States. The most serious was the 1993 Cryptosporidium outbreak in Milwaukee, in which 69 people died of complications arising from the outbreak.

Harrington's team will take a forward-looking view: Is there another emerging pathogen on the horizon that could unexpectedly threaten public health, in the same way crypto has in the past decade?

"Cryptosporidium is not the only microorganism of concern in drinking water," says Battigelli. "Although crypto has been the industry buzzword since 1993, we are finding other microorganisms which may also pose substantial risks to public health if left unaddressed."

There is reason to suspect a "new crypto" could be lurking, Harrington says. Since scientists have only recently been able to accurately detect many of the waterborne pathogens that cause illness, some newly-identified types may have been causing low levels of disease for years.

That's true of several pathogens in the study. A class of viruses called caliciviruses has been traced to recent waterborne outbreaks in the United States. The bacterium Escherichia coli 0157:H7, has caused at least two waterborne outbreaks that affected more than 300 people. In North and South America, the parasite Cyclospora has caused serious health problems for people relying on untreated drinking water.

Battigelli noted that medical treatment is not available for some diseases caused by these pathogens. In many cases, people rely exclusively on their body's immune system to fight them off. Mortality rates can be high among those with undeveloped or weakened immune systems, such as the very young, the elderly, chemotherapy patients, AIDS patients and transplant recipients.

In this project, the team will be studying viruses 100 times smaller than crypto - organisms which could more easily pass through some water-treatment technology. Other pathogens can be very resistant to the standard chemical treatment of chlorination.

The study will also help gauge performance of new water treatment technologies, which are becoming increasingly sophisticated. Those methods include dissolved air flotation and microfiltration. These treatments are more effective and more costly.

The crypto threat has driven a public willingness to pay for better and safer technologies, Harrington says. The city of Kenosha is installing a microfiltration system for city water, and the city of Milwaukee is upgrading its filters and installing ozonation.

Harrington emphasized that U.S. water-treatment standards are very good, and that drinking water is generally quite safe. Water utilities are required to have a multi-barrier approach to water treatment, where more than one technology is used to remove microorganisms.

"We could look at thousands of water samples before finding anything to worry about," he says. "But the consequences of failing to remove pathogens can be very large. We want to ensure there is minimal risk of public exposure."