Nonhazardous Urine Pretreatment Method for Future Exploration Systems

A nonhazardous urine pretreatment system prototype is proposed that will stabilize urine against biological growth or chemical instabilities without using hazardous chemicals. Untreated urine fosters biological growth, ammonia off-gassing, creation of bio-solids, and inorganic precipitates, which foul water and air reclamation hardware. The current Russian system employs hexavalent chromium, a strong oxidant and carcinogen, and sulfuric acid to stabilize urine (pH=1.8), while the future American system utilizes Oxone„¥, a strong oxidant, potassium hydrogen sulfate, and potassium benzoate to stabilize urine (pH=2.4). Urine stabilized by these methods requires triple and double containment, respectively. Chemical storage, handling, and delivery of pretreatment chemicals are also problematic due to their hazardous nature and low pH, which significantly increases Equivalent System Mass. The proposed prototype will utilize non-oxidizing biocides in combination with nontoxic and noncorrosive solid phase urine acidification to stabilize urine at much higher pHs (3.6-5.5). This approach has stabilized urine effectively for over 57 days during the Phase 1 program. The innovative prototype will fulfill an unmet need for safe, efficient, automated urine pretreatment for current and future NASA missions. The Phase 2 project will automate the nonhazardous urine pretreatment system, and deliver a fully functional Prototype suitable for testing at NASA facilities.