Urine Pretreatment Configuration and Test Results for Potential Space Station Applications

Pretreatment of urine using Oxone^® and sulfuric acid is baselined in the International Space Station (ISS) waste water reclamation system to control odors, fix Ammonia and control microbial growth. In addition, pretreatment is recommended for long term flight use of urine collection and two phase separation to reduce or eliminate fouling of the associated hardware and plumbing with urine precipitates. This is important to the ISS application because the amount of maintenance time for cleaning and repairing hardware must be minimized.

This paper describes the development of a chemical pretreatment system based on solid tablet shapes which are positioned in the inlet urine collection hose and are dissolved by the entrained urine at the proper ratio of pretreatment to urine. Building upon the prior success of the developed and tested solid Oxone tablet, a trade study and tests were completed to confirm if a similar approach would be appropriate for the sulfuric acid injection method. In addition, a recommended handling and packaging approach of the solid tablets for long term storage, as well as, safe and convenient use on ISS was addressed. Consequently, the solid tablet approach with suitable packaging was identified as the Urine Pretreat/Prefilter Assembly (UPPA).

Testing of the UPPA configuration confirmed the dissolution rates and ratios required by ISS were achieved. This testing included laboratory controlled methods as well as a ‘real world’ test evaluation that occurred during the 150 day Stage 10 Water Recovery Test (WRT) conducted at NASA Marshall Space Flight Center (MSFC).