Membrane distillation of synthetic urine for use in space structural habitat systems

Abstract

Low-energy separation of potable water from urine is an important area of research, particularly if humans hope to transcend their earth-bound origins. The high cost of water in rocket payloads means that it must be recycled and the byproducts of the crew used productively. Direct Contact Membrane Distillation (DCMD) can use low heat sources to separate water from urea, which can then be used as a plasticizer in regolith-based cement to make it more workable. In the present study, traditional cement curing was compared to vacuum curing for regolith-based cement where artificial urine, concentrated using DCMD, was added as a plasticizer. Increases in workability were found for increasing concentrations of urea. Porosity also tended to increase with increasing urea concentration. Surprisingly, Lunar Highlands Simulant regolith-based batches with urea that were cured under vacuum showed higher compressive strengths than those cured traditionally. No literature is available for DCMD use with urine, indicating that this research is novel and could have widespread applications, such as in desert environments or public urinals.