Demonstration of a Full Size Integrated Greywater Recycling System Combining Biological Pretreatment with Reverse Osmosis

Water is a critical limiting factor in long-term space habitation and water recovery systems are essential. Future habitation systems with partial gravity will likely have expanded hygiene activities (e.g. shower) and laundry. These wastewaters greatly increase the volume of wastewater to be treated. The combined hygiene, laundry and humidity condensate (greywater) has low organic carbon (151 mg/L), N (20 mg/L), and TDS (167 mg/L). Removal of the organic carbon allows subsequent use of membrane desalination systems. We demonstrate the operation of a full-size (4 crew/d) membrane aerated biofilm reactor (MABR) to pretreat habitation greywater prior to desalination using a commercially available RO system. Two commercially available membranes are being tested. To date over 8,000 L of greywater has been treated using this process. The bioreactor serves as a common collection tank for all wastewaters added as they are produced. In addition, the bioreactor did not require any start-up period. The bioreactor removed more than 90% of the DOC and total ammonia. The RO membrane (FilmTec) was able to operate for >3 months at moderate pressure (<50 PSI) at a 90% recovery rate. Permeate was near potable quality for DOC (3.5 mg/L), NH3 (0.2 mg/L), and TDS (6.5 mg/L). The production of permeate decreased over the 3 month period from 106.6 L/d to 57.6 L/d. Testing of the second membrane (AQUAPORIN) is ongoing. Our results highlight the ability of combined biological and membrane-based desalination to produce potable water with minimal consumables.