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Bioburden Control is one of the challenges for the Ultrapure Water System on Space Station Freedom. Bioburden Control must enable the system to deliver water with a low bacterial count (≤ 1 CFU/100 ml), as well as maintain biological contamination at a manageable level, to permit continued production of quality water. Ozone has been chosen as the primary means of Bioburden Control. Planned tests to determine the effectiveness of ozone on free-floating microbes and biofilms are described.

One objective of the Water Recovery Test (WRT) recently completed at NASA's Marshall Space Flight Center (MSFC) for the Environmental Control and Life Support System (ECLSS) of Space Station Freedom, was to determine the ability of the Water Recovery System to reclaim urine for crew reuse. In the process, raw urine is pretreated using a commercially available oxidant, Oxone (Dupont), and sulfuric acid (to reduce ammonia), and pumped into a urine processing subsystem. Recently, a combination of sodium hypochlorite and sulfuric acid has been considered as an alternative pretreatment. This study examined the ability of these pretreatments, plus a third pretreatment utilizing ozone, to reduce microbial levels in raw urine. In addition, the corrosion rate of titanium-6AL-4V, a candidate material for the water system of Space Station Freedom, was monitored in the presence of these pretreatments using weld and base metal specimens.