A simple and reliable technique facilitates the addition of silver ions to water supplies to suppress bacterial contamination. In the original application for which the technique was devised, there is a need for Ag+-ion concentrations at a biocidal levels (0.5 mg/L) in 44-L batches of drinking water. The technique involves the preparation of a solution of concentrated biocide by dissolving 0.66 g of AgF and 1.04 g of NaF in 0.5 L deionized water. Batches of the solution are put into plastic syringes that have volumes of 20 cm3 each and are equipped with fittings for connection to the water supplies to be treated. The syringes are capped and placed in plastic bags for transport and storage. The shelf life of the syringes stored at room temperature is at least two years. When needed, a syringe is simply unpacked and connected to a mating fitting on a water supply. The concentrated solution is then injected into the flowing water, wherein the solution becomes diluted to the desired final concentration.
This work was done by Richard L. Sauer of Johnson Space Center and Paul D. Mudgett and John R. Schultz of Wyle Laboratories. For further information, access the Technical Support Package (TSP) free on-line at www.nasatech.com/tsp under the Materials category.