Silver and UV radiation combined may be more effective and timely at disinfecting drinking water and wastewater say researchers from the U.S. Military Academy, West Point, New York. Their findings appear in the May 2004 issue of the journal Applied and Environmental Microbiology.
Commonly used as a co-disinfectant in swimming pools and hospital hot water systems since the mid-1800's, silver has been somewhat effective at bactericidal activity with little or no harmful side effects in humans. However, researchers have found that there are organisms resistant to silver and that lengthy exposure time is necessary for disinfection to occur. Ultra-violet (UV) radiation is a more recently developed method shown to inactivate protozoa in water. The main concern associated with UV radiation is elevated cost due to extended operation periods.
In the study, coliphage MS-2, considered to be a practical surrogate for pathogenic viruses, was exposed to silver individually and then combined with UV radiation. Results showed that when exposed to only silver for ten minutes little inactivation occurred, but ten minute exposure time to silver followed by UV radiation resulted in a disinfectant rate of 99.5 %. The silver/UV radiation combination appears to minimize exposure time and operation costs while achieving maximum inactivation of the virus.
"The data clearly shows that there is a synergistic effect when silver and UV radiation are combined," say the researchers. "Because it has also been reported for a DNA virus, it is expected that the synergistic effect between silver and UV radiation might also exist for the inactivation of pathogenic viruses such as poliovirus, noroviruses, and the enteric adenovirus types."
(M.A. Butkus, M.P. Labare, J.A. Starke, K. Moon, M. Talbot. 2004. Use of aqueous silver to enhance inactivation of
Contact: Jim Sliwa
American Society for Microbiology