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With the installation of the Water Recovery System (WRS) during mission STS-126 in 2008, the International Space Station (ISS) added the capability to recover clean water for reuse from crewmember urine and atmospheric humidity condensate, including EVA (Extravehicular Activity) wastes. The ability to collect, store and process these waste streams is required to increase potable water recovery and support the ISS crew augmentation planned for 2009. During ground testing of the Urine Processing Assembly (UPA), one of two primary component subsystems that comprise the WRS, significant fouling was repeatedly observed in stored urine pretreated with 0.56% of chromium trioxide and sulfuric acid. During initial observation, presumptive microbiological growth clogged and damaged flight-rated hardware under test as part of a risk-mitigation Flight Experiment (FE).

This report describes proof-of-concept testing of a commercial-off-the-shelf deep ultraviolet LED for future application as a point-of-use or residual disinfection device for spacecraft potable water systems. The electro-optical performance and disinfection efficacy of a 0.5 mW 265nm UV-C LED (UVTOP, Sensor Electronic Technology, Inc., Columbia, SC) was measured in both static and flow environments against five challenge microorganisms inoculated into potable water at an initial concentration ≥ 108 cells per milliliter. The germicidal irradiation from a single UV-C LED array was sufficient to effect > 4-log kill (> 99.99%) of the challenge bacterial population in < 60 minutes contact time.