Every gallon of purified drinking water is home to hundreds of millions of bacteria. Water treatment facilities try to remove them – but perhaps encouraging some of the microbes to grow could benefit human health.
Lutgarde Raskin of the University of Michigan in Ann Arbor says that workers at water treatment facilities across the US try to destroy all of the bacteria in drinking water with infusions of chlorine and other disinfectants. But this is nearly impossible to achieve with the current technology.
The present approach also ignores the fact that the drinking water microbiome contains some bacteria that can be beneficial. For instance, nitrates that can contaminate drinking water could be converted by some bacteria into harmless nitrogen gas. Raskin and her team suggest that encouraging the growth of these bacteria in drinking water could actually improve the quality and safety of the product.
Between April and October 2010, the researchers analysed bacterial DNA in drinking water treated at municipal facilities in Ann Arbor. They wanted to work out exactly which bacteria were present, and what factors influenced the abundance of the various components of the bacterial community.
They found that slightly altering the water's pH during the filtration process, or even changing how filters were cleaned, helped good bacteria outcompete more harmful microorganisms for the limited resources in the water.
"It does no good to try to remove bacteria entirely," says Raskin. "We are suggesting that a few simple changes can be made that will give bacteria that are good for human health an edge over harmful competitors."