DISINFECTION OF WATER

Elemental iodine (I2) is used for disinfection of reclaimed waters in all American designed systems. The Russian space program utilizes silver ion (Ag+). The two species are mutually incompatible. Each of the biocides, and the problems which must be overcome in joint Russian-American missions are disscussed below:

IODINE

Disinfection of the drinking water supplies aboard spacecraft is a requirement for the maintenance of flight crew health. Current NASA specifications for potability limit the maximum microbial population to less than 100 Colony Forming Units (CFU)/100mL, with total coliforms less than 1 CFU/100mL. Elemental iodine (I2) was first applied as a drinking water disinfectant on U.S. spacecraft in the Lunar Module during the Apollo missions which began in 1969. Prior to each mission, Lunar Module drinking water storage tanks were prefilled with water containing an I2 concentration of 12mg/L. This level was sufficient to maintain a residual disinfectant concentration of < 0.5mg/L. During the Skylab mission potable water tanks were iodinated to 12mg/L I2 prior to launch. Afterward aqueous elemental iodine concentrations were monitored and maintained in the range between 0.5-6.0mg/L by direct additions to the water storage tanks during flight using a 30g/L stock solution containing potassium iodide (KI) and I2 in a 2:1 molar ratio.

For the Space Shuttle program, a new device for the controlled release of I2 termed the Microbial Check Valve (MCV) was introduced. The MCV is a canister containing iodinated strong base ion exchange resin. In aqueous solution in the presence of excess iodide (I-), polyiodide anions are formed,

MCV resin consists of polyiodide anions bound to the quaternary amine fixed positive charges of a polystyrene-divinylbenzene copolymer anion exchange resin. The bound polyiodide anions release I2 to water.

Onboard the Space Shuttle, high purity water produced by the fuel cells flows through an MCV canister which provides both a contact microbial kill and imparts an elemental iodine residual ranging between 0.5-4.0 mg/L. Similar devices are installed at the Galley Auxiliary Port and the Extravehicular Mobility Unit Service and Cooling Umbilical for microbial control. The MCV has proven effective as a means for maintaining drinking water potability and in ground based tests has demonstrated a remarkable ability to inhibit the growth of biofilm.

Aboard the Shuttle Orbiter all MCV canisters require periodic replacement. To simplify resupply logistics for future longer duration missions, regenerative MCV (RMCV) hardware has been developed. This technology utilizes a packed bed of crystalline elemental iodine to produce a saturated aqueous solution ([I2] = 300mg/L) which is used to replenish depleted MCV® resin.

REFERENCES

Atwater, J.E., Wheeler, R.R., Jr., Sauer, R.L., and Schultz, J.R., Advanced Development of the Regenerative Microbial Check Valve, SAE 932175, presented 23rd International Conference on Environmental Systems, Colorado Springs, July, 1993.

Atwater, J.E., Wheeler, R.R., Jr., Olivadoti, J.T., and Sauer, R.L., Chemistry and Kinetics of I2 Loss in Urine Distillate and Humidity Condensate, SAE 921314, presented at 22nd International Conference on Environmental Systems, Seattle, July, 1992.

Atwater, J.E., Wheeler, R.R.,Jr., Olivadoti, J.T., Flanagan, D.T. and Sauer, R.L., Regenerable Microbial Check Valve: Life Cycle Tests Results, SAE Trans. J. Aerosp., 101, 1098, 1992.

Barkley, R., Hurst, C., Dunham, A., Silverstein, J., and Brion, G.M., Generation of Iodine Disinfection By-Products (IDP's) in a Water Recycle System, SAE Technical Paper Series No. 921362, presented 22nd International Conference on Environmental Systems, Seattle, WA, July 13-16, 1992.

Brion, G.M., and Silverstein, J., Inactivation of a Model Coliphage Virus in Water by Iodine, SAE Technical Paper Series No. 921361, presented 22nd International Conference on Environmental Systems, Seattle, WA, July 13-16, 1992.

Bull, R.J., Thrall, K.D., and Sherer, T.T., Thyroid Effects of Iodine and Iodide in Potable Water, SAE Technical Paper Series No. 911401, presented 21st International Conference on Environmental Systems, San Francisco, CA, July 15-18, 1991.

Cioletti, L.A., Mishra, S.K., Pierson, D.L., and Koenig, D.W., Microbiology Standards for the International Space Station, SAE Technical Paper Series No. 951682, presented at 25th International Conference on Environmental Systems, San Diego, CA, July 10-13, 1995.

Colombo, G.V., Jolly, C.D., and Sauer, R.L., Regenerable Biocide Delivery Unit, SAE Technical Paper Series No. 911406, presented 21st International Conference on Environmental Systems, San Francisco, CA, July 15-18, 1991.

Colombo, G.V., and Sauer, R.L., Review of Water Disinfection Techniques, SAE Technical Paper Series No. 871488, presented 17th Intersociety Conference on Environmental Systems, 1987.

Colombo, G.V., and Sauer, R.L., Special Problems and Solutions to Potable Water Disinfection in Spacecraft, presented at Conference on Progress in Chemical Disinfection: New Concepts and Materials, Birmingham, N.Y., March 26 - 27, 1982.

Colombo, G.V., and Putnam, D.F., Microbial Check Valve for Shuttle, ASME Paper 78-ENAs-27, presented at 8th Intersociety Conference on Environmental Systems, San Diego, July 10-13, 1978.

Ford, T., Maki, J.S., and Mitchell, R., Biodeterioration of Materials in Water Reclamation Systems, SAE Technical Paper Series No. 921311, presented 22nd International Conference on Environmental Systems, Seattle, WA, July 13-16, 1992.

Glass, J.I., Lefkowitz, E.J., Roman, M.C., Cassell, G.H., In-Line Microbial Monitor for the Analysis of Recycled Water Aboard ISS: Issues and Prospects, SAE Technical Paper Series No. 961568, presented 26th International Conference on Environmental Systems, Monterey, CA, July 8-11, 1996.

Koenig, D.W., Bell-Robinson, D.M., Johnson, S.M., Mishra, S.K., Sauer, R.L., and Pierson, D.L., Microbiological Analysis of Water in Space, SAE Technical Paper Series No. 951683, presented at 25th International Conference on Environmental Systems, San Diego, CA, July 10-13, 1995.

Koenig, D.W., Mallary, L.L., and Pierson, D.L., Disinfectants for Spacecraft Applications: An Overview, SAE Technical Paper Series No. 911516, presented 21st International Conference on Environmental Systems, San Francisco, CA, July 15-18, 1991.

Marsh, R.W., Grabowski, N.A., and Steele, J.W., Space Station Condensing Heat Exchanger Biofilm Formation and Control Evaluation, SAE Technical Paper Series No. 921383, presented 22nd International Conference on Environmental Systems, Seattle, WA, July 13-16, 1992.

McFeters, G.A., Pyle, B.H., Watters, S.K., Cargill, K.L., and Yu, F.P., Disinfection Susceptibility of Waterborne Pseudomonads and Legionellae Under Simulated Space Vehicle Conditions, SAE Technical Paper Series No. 911402, presented 21st International Conference on Environmental Systems, San Francisco, CA, July 15-18, 1991.

Obenhuber, D.C., Huff, T.L., Rodgers, E.B., Microbial Biofilm Studies of the Environmental Control and Life Support System Water Recovery Test for Space Station Freedom, SAE Technical Paper Series No. 911378, presented 21st International Conference on Environmental Systems, San Francisco, CA, July 15-18, 1991.

Pyle, B.H., and McFeters, G.A., Microbiological Concerns and Methodological Approaches Related to Bacterial Water Quality in Spaceflight, SAE Technical Paper Series No. 921232, presented 22nd International Conference on Environmental Systems, Seattle, WA, July 13-16, 1992.

Roman, M.C., Wilson, M.E., Jackson, N.E., Gauthier, J.J., Kilgore, B.A., Huff, T.L., Obenhuber, D.C., and Terrell, D.W., Microbial Distribution in the Environmental Control and Life Support System Water Recovery Test Conducted at NASA, MSFC, SAE Technical Paper Series No. 911377, presented 21st International Conference on Environmental Systems, San Francisco, CA, July 15-18, 1991.

Rutz, J.A., Muckle, S.V., and Sauer, R.L., Iodine Addition Using Triiodide Solutions, SAE Technical Paper Series No. 921315, presented 22nd International Conference on Environmental Systems, Seattle, WA, July 13-16, 1992.

Sauer, R.L., Colombo, G.V., and Jolly, C.D., Regenerable Biocide Delivery Unit, U.S. Patent 5,176,836, 1993

Schultz, J.R., Flanagan, D.T., Bruce, R.J., Mudgett, P.D., Carr, S.E., Rutz, J.A., Huls, M.H., Sauer, R.L., and Pierson, D.L., Biofilm Formation and Control in a Simulated Spacecraft Water System: Three Year Results, SAE Technical Paper Series No. 921310, presented 22nd International Conference on Environmental Systems, Seattle, WA, July 13-16, 1992.

Schultz, J.R., et al., Biofilm Formation and Control in a Simulated Spacecraft Water System: Two Year Results, SAE Technical Paper Series No. 911403, presented 21st International Conference on Environmental Systems, San Francisco, CA, July 15-18, 1991.

Schultz, J.R., Taylor, R.D., Flanagan, D.T., Gibbons, R.E., Brown, H.D., Sauer, R.L., and Pierson, D.L., Biofilm Formation and Control in a Simulated Spacecraft Water System: Interim Results, SAE Technical Paper Series No. 891543, presented 19th Intersociety Conference on Environmental Systems, San Diego, CA, July 1989.

Stroup, T.L., Schwartzkopf, S.H., and Marchin, G.L., Iodine Microbial Control of Hydroponic Nutrient Solution, SAE Technical Paper Series No. 911490, presented 21st International Conference on Environmental Systems, San Francisco, CA, July 15-18, 1991.

Willis, C.E., and Schultz, J.R., Spacecraft Water System Disinfection Technology: Past, Present and Future Needs, SAE Technical Paper Series No. 871487, presented 17th Intersociety Conference on Environmental Systems, Seattle, WA, July 1987.

* MCV® Resin is a Registered Trademark of UMPQUA Research Company.

Copyright © 1996, James E. Atwater