Cleaner drinking water with fewer chemicals may be made possible using ... bacteria.

A research team studied four bacteria, Sphingobium, Xenophilus, Methylobacterium and Rhodococcus, found in a city's drinking water to see which combinations were more likely to produce a 'biofilm'. Biofilms are layers of bacteria which form on the inner surfaces of water pipes. Like in many instances, bacteria can be harmful or not.

"If the bacterial growth is too heavy, it can break off into the water flow, which at best can make water discoloured or taste unpleasant and at worst can release more dangerous bacteria. Our research looks at what conditions enable biofilms to grow, so we can find ways to control the bacteria in our water supply more effectively," explains lead researcher Professor Catherine Biggs.

The researchers isolated four bacteria from water taken from a domestic tap: two were widely found in drinking water everywhere, one was less common and one was unique to Sheffield. The researchers mixed the bacteria in different combinations and found that, in isolation, none of them produced a biofilm. 

However, when any of the bacteria were combined with Methylobacterium, one of the common forms, they formed a biofilm within 72 hours.

"Our findings show that this bacterium is acting as a bridge, enabling other bacteria to attach to surfaces and produce a biofilm and it's likely that it's not the only one that plays this role," says Professor Biggs. "This means it should be possible to control or even prevent the creation of biofilms in the water supply by targeting these particular bacteria, potentially reducing the need for high dosage chemical treatments."

Domestic water supplies in the UK are regularly tested for levels of bacteria and, if these are too high, water is treated with greater concentrations of chlorine or pipe networks are flushed through to clear the problem. However, the standard tests look for indicator organisms rather than the individual types which are present. Testing methods being developed by the Sheffield team – as used in this research – involve DNA analysis to identify the specific types of bacteria present.

"The way we currently maintain clean water supplies is a little like using antibiotics without knowing what infection we're treating," says Professor Biggs. "Although it's effective, it requires extensive use of chemicals or can put water supplies out of use to consumers for a period of time. Current testing methods also take time to produce results, while the bacteria are cultured from the samples taken.

"The DNA testing we're developing will provide a fast and more sophisticated alternative, allowing water companies to fine tune their responses to the exact bacteria they find in the water system."

Citation: B. Ramalingam, R. Sekar, J. B. Boxall and C. A. Biggs, 'Aggregation and biofilm formation of bacteria isolated from domestic drinking water', Water Science  &  Technology: Water Supply Vol 13 No 4 pp 1016–1023 2013 doi:10.2166/ws.2013.115