1993-07-01

Advanced Development of the Regenerative Microbial Check Valve 932175

The Microbial Check Valve (MCV) is a reloadable flow-through canister containing iodinated ion exchange resin, which is used aboard the Shuttle Orbiter as a disinfectant to maintain water potability. The MCV exhibits a significant contact kill and imparts a biocidal residual I2 concentration to the effluent. MCVs in current use have nominal 30 day lives. MCVs baselined for Space Station Freedom will have 90 day lives, and will require replacement 120 times over 30 years. Means to extend MCV life are desirable to minimize resupply penalties.
New technology has been developed for fully autonomous in situ regeneration of an expended MCV canister. The Regenerative Microbial Check Valve (RMCV) consists of an MCV, a packed bed of crystalline I2, a flow diverter valve, an in-line iodine monitor and a microcontroller. During regeneration, flow is directed first through the packed I2 bed and then into the MCV where the resin is replenished. RMCV life cycle tests have been conducted over an eighteen month period using challenge streams simulating reclaimed potable water, reclaimed hygiene water, humidity condensate, and urine distillate. MCV life extensions of up to 130 fold have been achieved, limited only by the time constraints of the test program. A full scale and fully autonomous prototype RMCV has been constructed and operationally tested, demonstrating precise control of residual I2 levels within the desired 2.0 - 4.0 mg/L concentration range, and demonstrating capability of unattended operation for prolonged periods.
An additional benefit of RMCV technology is the capability for on demand production of a strong disinfectant via a completely reagentless methodology. Flow through the packed I2 crystal bed produces a highly concentrated aqueous I2 solution which can be effectively applied to the decontamination of external surfaces, the control of biofilm formation, and as a preventive measure in systems vulnerable to microbial growth and biofilm formation.

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