Viruses Migrate From Sewers To Drinking-Water Wells

Over the past decade, researchers have been finding disease-causing viruses in municipal wells in the U.S. and Europe, a cause of concern if the water isn’t disinfected. Now, a team of scientists has traced and definitively linked these invading viruses to nearby sewage systems (Environ. Sci. Technol., DOI: 10.1021/es400509b).

Scientists once thought that human pathogens, such as diarrhea-causing adenoviruses, that end up in the environment couldn’t reach deep, protected aquifers. Even if the pathogens did find their way to the groundwater, it would take years and they would likely die during that time. But these assumptions may not always hold, researchers say.

Kenneth R. Bradbury, a hydrogeologist at the University of Wisconsin-Extension, in Madison, and his team launched a sampling program to periodically test both sewage at a Madison waste-treatment plant and water pumped from area municipal wells. The researchers identified viruses and measured their concentrations by analyzing viral nucleic acids using a real-time quantitative polymerase chain reaction method.

A few weeks after viruses were detected in the sewage, the same viruses appeared in the wells, usually after a rain or snowfall melt. What’s more, the scientists cultured the viruses from the wells and showed that they were still infectious. “Because Madison chlorinates its water, no one has become sick,” Bradbury says.

Bradbury thinks the contamination problem probably occurs in any city with wells located under sewage pipes. In the U.S., more than 147,000 public water systems supply drinking water from underground aquifers to some 100 million people. About two-thirds of these systems don’t disinfect the water.

Nicholas J. Ashbolt, a microbiologist with expertise in the transport of environmental pathogens, says the study “should be a warning flag to those who think that confined aquifers are safe from the impact of pathogens.” He recommends that public water systems assess their vulnerability to contamination and decide whether they should test for viruses on a routine basis.