New Concepts and Performance of the Direct Osmotic Concentration Process for Wastewater Recovery in Advanced Life Support Systems

Direct osmotic concentration (DOC) has been identified as a potential wastewater treatment process for potable reuse in advanced life support systems (ALSS). As a result, further development of the DOC process is being supported by a NASA Rapid Technology Development Team (RTDT) program. DOC is an integrated membrane system combining three unique membrane separation processes including forward osmosis (FO), membrane distillation (MD), and reverse osmosis (RO) that is designed to treat separate wastewater streams comprising hygiene wastewater, humidity condensate, and urine. An aqueous phase catalytic oxidation (APCO) process is incorporated as post treatment for the product water. In an ongoing effort to improve the DOC process and make it fully autonomous, further development of the three membrane technologies is being pursued. In the area of FO for the treatment of hygiene wastewater, new membranes are being investigated for their performance, including, water flux and rejection of surfactants, nutrients, and minerals. New design of the RO subsystem resulted in increased stability of operation for extended time. Results from MD of urine and humidity condensate revealed that this process is a viable solution. Both MD and FO were tested and showed high rejection of endocrine disrupting chemicals (EDCs).