Bacteria in tap water traced to the water treatment process

commonly used to remove suspended particles play a significant role in determining which bacteria are most prevalent in treated drinking water.

The release notes that the relative abundance of Alphaproteobacteria, for example, was found to be around 6 percent in source water, but 38 percent on the filters, and 23 percent of the bacterial community at the tap.

This pattern occurred despite regular filter cleaning. These mostly harmless bacteria were able to form biofilms on the filters, slough off into the water, and survive the disinfection process.

Water suppliers typically add chemicals such as chlorine to drinking water, but these disinfectants can react with naturally occurring substances in the water to form potentially harmful byproducts, according to the EPA. Many of these byproducts themselves are regulated.

Disinfection can form harmful chemicals in drinking water,” said Chuanwu Xi, associate professor of environmental health sciences in the School of Public Health, who participated in this study. “If we can get away with not using so many chemicals and prevent the formation of these byproducts, we should think about limiting their use.”

The researchers suggest that these filters could serve as early indicators of the presence of beneficial and disease-causing bacteria. They could be regularly tested, and pathogens might be contained there to prevent them from reaching the distribution system. The filters also could potentially be re-engineered to support the growth of beneficial or neutral bacteria.

We hope to begin research to explore how to improve public health by engineering drinking water treatment plants to impact the drinking water microbiome, perhaps by promoting growth of beneficial microbes that outcompete pathogenic microbes,” Raskin said. “We think it is feasible to do this in the long run.”

Current regulations and engineering practices focus on removing chemical and microbial contaminants from the source water to provide safe and clean water and protect the public from waterborne diseases,” Xi said. “In addition to the protection we have already, there is potential to add benefits to the water we consume everyday for improving our health, for example, by having a positive impact on the microbial community in the human gut. More research is needed to evaluate this potential beneficial impact when we move in that direction.”

The work was funded by the National Science Foundation.

— Read more in Ameet J. Pinto et al., “Bacterial Community Structure in the Drinking Water Microbiome Is Governed by Filtration Processes,” Environmental Science and Technology (16 July 2012) (DOI: 10.1021/es302042t)