Full-Scale Humidity Condensate Treatment Using a Hybrid Treatment System: Membrane Aerated Biological Pretreatment and Reverse Osmosis

The development of efficient and sustainable water recycling systems is essential for long-term human missions and the establishment of space habitats on the Moon, Mars, and beyond. Humidity Condensate (HC) is a low strength wastewater that is currently recycled on ISS. The HC contaminants are primarily low molecular weight organics and ammonia. This has caused operational issues due to microbial growth in the water processor assembly WPA storage tank and failure of down-stream systems. In addition, treatment of this wastewater primarily uses adsorptive and exchange media, which must be continually resupplied. This study demonstrates the integration of a biological reactor for pre-treatment of HC coupled to a low pressure (<60PSI) Reverse Osmosis (RO) system. The bioreactor is a Membrane Aerated Bioreactor (MABR) which supports micro-gravity compatible aeration and can serve as the HC storage tank. The system was tested in two configurations, with and without an RO recycling tank. The MABR was challenged with a 4 crew-day load and the RO system was run until a single membrane could not process the 4-crew-day load in < 24 hours. Current results indicate that the MABR removes > 80% DOC and that a single RO membrane (260 grams) can process > 3000 L of wastewater. RO effluent is near potable water reducing the need for post treatment and thus reducing consumable consumption. The results suggest that this hybrid system has the potential to significantly enhance the self-sufficiency of space habitats, supporting sustainable extra-terrestrial human habitation as well as reducing current operational problems on ISS.