Pervaporation for Recovering Clean Water from Real Urine in Partial Gravity Habitats

Over the last decades, substantial progress has been made in developing water treatment processes for partial gravity habitats on the Moon and Mars. In this context, Lenntech Water Treatment Solutions and DeltaMem AG have explored the use of pervaporation to recover clean water from real urine for application in planetary habitats. Pervaporation offers several advantages over other evaporation technologies, primarily due to membrane properties, yielding a higher purity of treated water by preventing the permeation of volatile contaminants. This study evaluated the performance of polymeric pervaporation membranes in removing ionic salts and organic compounds from real urine at up to 92% water recovery. The quality of the condensate was monitored over time throughout the experiments and the replicability of the results was assessed over multiple batches with the same membrane. A total exposure time of 28 days of the membrane to real urine allowed to assess the durability of the membrane over an expected mission duration. The pervaporation membrane showed a salt TDS removal of 99.7% and an organic contaminant removal exceeding 99.9%, resulting in a condensate conductivity of 25 ± 6 µS/cm and a total organic carbon concentration of 3.5 ± 1.2 mg/L, respectively. Triplicate experiments confirmed replicability of the results and durability of the membrane over the experimental period. In summary, this works highlights the performance of pervaporation in recovering clean water from real urine. This research lays the groundwork for future endeavors, focusing on pervaporation system optimization, membrane module prototyping and extended testing phases, to fully meet the criteria of a urine processor for partial gravity habitat.