PITA Fiscal Year 2008 Projects - Biomedical and Health Engineering

Silver Disinfection Studies

Silver is a natural antibacterial agent which has been used for centuries in various forms to eliminate bacterial growth on surfaces and in water supplies. A silver ion electrolysis system was used by NASA to purify drinking water on the Apollo missions in the 1960s, and a number of manufacturers of water purification systems (e.g., Pur, Brita, and Katadyn) are now incorporating some form of silver into their products for disinfection purposes. Colloidal silver has also been used with ceramic water filtration systems in developing countries to kill waterborne bacteria in drinking water. While silver has been used throughout history and into the current age as a disinfectant, relatively few studies regarding the actual mechanism by which silver interacts with microorganisms have been performed. It remains unclear how the speciation of silver affects disinfection or if silver needs to be bioavailable and uptaken by microorganisms for effective inactivation. Furthermore, the effects of silver on Cryptosporidium oocysts, protozoan pathogens which are resistant to conventional chlorine disinfection, have not been reported.

The objective of the proposed work is to assess the effects of different silver speciations on E. coli and Cryptosporidium in order to develop a better understanding of the mechanism of disinfection. Preliminary work has shown that silver holds promise as a disinfectant against Cryptosporidium. If silver proves successful for disinfecting bacteria and chlorine-resistant microorganisms from drinking water supplies, the technology could prove useful for drinking water disinfection at the personal, household, and municipal levels. This technology would be attractive to many different kinds of users as well, including outdoor enthusiasts, military personnel, water utilities, and rural citizens in developing countries.