To Biocide or not to Biocide? Exploring the "No Biocide" Option in Spacecraft Potable Water Systems



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2023 International Conference on Environmental Systems


Residual biocide has been used to protect against microbial growth in spacecraft potable water systems since the Gemini program. Iodine, the biocide currently used on the International Space Station (ISS) has a long history of use but presents a few challenges for exploration: it must be removed using a consumable absorbent before crew consumption and is known to lose its biocidal concentration due to interactions with wetted components, especially during periods of dormancy. Biocidal silver is being considered for exploration missions as it is safe for crew consumption, but it too has challenges with proper material design to maintain sufficient disinfection residuals. An idea proposed by some in the Environmental Control and Life Support System (ECLSS) community has been that the biocide does not provide a true barrier against microbial growth, and therefore, perhaps the challenges of maintaining a residual biocide in the system could be best overcome by removing the biocide altogether. In this argument, they point to the regenerative water treatment system on the ISS which produces high purity water that theoretically meets the microbiological requirements before the iodine is added. Exploration water processing systems are expected to have similar water processing capabilities. This paper will discuss the role that residual biocide may play in controlling microbial growth and presents perspectives on the potential risks associated with removing it from exploration water systems.


Mary Lou Nadeau, Aerodyne Industries LLC, USA
Audry Almengor, JES Tech, USA
Dean Muirhead, Barrios Technology, USA
Mark Ott, NASA Johnson Space Center, USA
Michael Callahan, NASA Johnson Space Center, USA
ICES303: Physio-Chemical Life Support- Water Recovery & Management Systems- Technology and Process Development
The 52nd International Conference on Environmental Systems was held in Calgary, Canada, on 16 July 2023 through 20 July 2023.


biocide, spacecraft potable water, microbial growth