A successful urine pretreatment method was developed during a NASA SBIR Phase Ⅱ grant program that stabilizes stored urine against microbial proliferation and chemical imbalance at a moderate pH of 4 without the use of hazardous chemicals. Success was demonstrated by effective stabilization of a large number of composite urine samples using low concentrations of non-oxidizing biocides. The pretreatment formula contains a quaternary amine and sodium benzoate as primary and secondary biocides, and an organic acid for acidification. The nonhazardous nature of the urine pretreatment constituents is exemplified by the approval of the quaternary amine for human use as a biocide, the acceptance of sodium benzoate as an antifungal agent in food, and the use of organic acids as food preservatives. Urine pretreatment in use aboard the International Space Station (ISS) is based upon the strong oxidant, hexavalent chromium, and operates at a pH < 1.8, which necessitates triple containment. This carcinogenic oxidant generates harmful oxidation products in urine and is rapidly rendered inactive by oxidation-reduction reactions. In comparison, the nonhazardous urine pretreatment chemicals are stable and safe to handle with benign storage and use requirements. These characteristics will lower urine pretreatment Equivalent System Mass (ESM) by decreasing containment volume and mass, expendable chemical mass, system complexity, and crew time needed to handle pretreatment chemicals.
展开▼
