NASA uses a biocide to prevent contamination of astronaut drinking water with harmful microorganisms. Concerns have arisen over existing biocides — that they’re inadequately effective, and may have toxic side effects when consumed. New microbial control methods are a priority. This need is addressed by using an electrochemical reactor for on-demand generation of hydrogen peroxide (H2O2) solutions. The device uses onboard resources only. The method eliminates the need for resupply items (reducing launch costs), and reduces toxicity risk.
The objective of this project is to demonstrate the feasibility of ondemand production of H2O2 as a biocide for long-duration space missions. H2O2 is produced by a novel electrochemical generator, which uses a polymer membrane as the electrolyte (not a liquid). It is an effective biocidal and biostatic agent. It is highly soluble in water, and the risks associated with its use are minimized because it decomposes, leaving only benign end products (H2O and O2). At concentrations used for disinfection, H2O2 has very good materials compatibility characteristics.
In addition, H2O2 has been extensively and safely used as a food preservative, in dental and other hygiene and medical products, and on food processing equipment and food contact articles. The ondemand generator eliminates the need for resupply, and can offer operational flexibility, capable of being activated to generate high amounts to address excess bioburden, or adjusted to produce low residuals for water quality maintenance. Its use may also be complementary to existing iodine and silver biocides. In this invention, the use of H2O2 to complement the use of iodine and silver biocides is proposed. One potential scenario for H2O2 in space potable water systems is for the temporary use of H2O2 when it has been determined that iodine (or silver biocide) is not effective. This is quite relevant for the International Space Station (ISS), where H2O2-generating devices could be used to support ongoing efforts to maintain water quality aboard the ISS in response to the emergency of biocide-resistant microbes. In addition to chemical compatibilities (i.e., H2O2 is not chemically reactive with other biocides), there may be a synergistic effect where the microbial inactivation is higher when iodine (or silver biocide) and H2O2 are present over the sum of the effect of each one of them independently.
With regard to the water dispensing system, the system can be sized to provide the H2O2 level needed for crew water demands, and then operate intermittently as needed, based on H2O2 levels within the storage tank.