Humidity Condensate Treatment using a Hybrid Life Support System

Treatment of space habitation wastewaters to produce potable water is a requirement for sustainable space habitation. Current micro-gravity systems use only physical or chemical processes. In addition, wastewaters must be stored prior to treatment. For future space habitats particularly in reduced gravity a variety of wastewaters may be produced including shower, hygiene, and laundry, but for any space habitat in micro-gravity or reduced gravity, humidity condensate and urine will always be produced. On station humidity condensate makes up about fifty percent of the produced wastewater. Storage of this wastewater prior to processing in the WPA is problematic because it is biologically active. Biomass produced in the storage tank or which grows downstream can and has caused failures due to clogging of filters or valves. The root cause of the growth is the presence of organic carbon which supports growth. Removal of this organic carbon would prevent system failures and produce a near potable water. This research effort evaluated the use of a hybrid treatment system which included a membrane aerated bioreactor coupled to a low-pressure reverse osmosis system to treat humidity condensate. For this study, the bioreactor acted as both the collection tank and RO recycle tank, which allowed the system to operate without production of brine. The system was run for over 200days and treated 1,100 L and the RO process produced 1,100 L of permeate with a DOC<10 mg-C/Land TDS< 100 mg/L for 170 days. Consumables consisted of only the RO membrane (260g/1000kg of treated water) and prefilter (227g/1000kg of treated water) and consumed O2 (162g/1000kg of treated water). While the system could not operate indefinitely due to the increase in TDS, it does highlight the ability to remove organic carbon and operate for an extended period with brine production.