US scientists have taken a step towards using water filters to help detect biological agents released into domestic water supplies.

Driven by concerns that terrorists could release water borne agents - such as bacteria and viruses - into fresh water supplies, Geoffrey Smith and colleagues at New Mexico State University, Las Cruces, developed a bioagent detection method using carbon block water filters as sampling devices.

These carbon block water filters are attached to taps in 11% of US households to remove organic and inorganic compounds and trap microorganisms, such as bacteria.  

Smith tested the potential of the filters by simulating bioagent release. Bacillus atrophaeus spores, Escherichia coli and the PP7 virus were used as surrogates for real agents, and the filters exposed to these in chlorinated water.  He found that two popular brands of these filters trapped 92-99% of surrogate agents.  An efficient extraction method was also developed, using an eluent containing protein-based compounds and a non-ionic surfactant, to remove the microbes from the filters so that they could be recovered and identified.  

Smith found that Bacillus atrophaeus spores could be recovered from the filters up to five days after it had been removed from the tap provided it was refrigerated. They also found that that chlorine in the water inactivated E. coli and the PP7 virus.

Clive Thompson, a chief scientist at ALcontrol Laboratories in Rotherham, UK, says that this technique could easily be implemented in an emergency situation.  The same filters could also concentrate potential chemical agents which could be extracted and analysed, he adds.

Nicola Burton