Urine Pretreatment in Advanced Water Recovery Systems for Human Space Exploration

The National Aeronautics and Space Administration's (NASA) future plans for long-term spaceflight will require a wastewater recovery system in order to supply enough water to complete missions. The primary sources for wastewater in manned spacecraft are humidity condensate, hygiene water and urine. Prior to wastewater collection, urine is pretreated in order to prevent clogging of the small diameter collection tubes by biofilm formation and solids precipitation. The current urine pretreatment chemicals are toxic and contaminate the other sources of wastewater preventing the reclamation of potable water. The objective of this research was to identify nontoxic urine pretreatment agents that best prevent solids precipitation and bacterial growth. Two acids, glycolic and acetic, were chosen based on their desirable oxidative properties and low pKa values. Both chemicals maintained constant concentrations of Total Suspended Solids (TSS), which indicates that urine precipitation was prevented, and pH levels in the range of two to four. Conflicting test results for the prevention of bacterial growth were inconclusive based on the nitrate and ammonia concentration trends.