Next Generation Life Support (NGLS): Alternate Water Processor (AWP)

The Alternative Water Processor (AWP) is an integrated biological and physicochemical system for recycling wastewater from multiple sources expected in future exploration missions, including hygiene and laundry water.  Organic constituents in the wastewater are mineralized by a membrane-aerated biological reactor, a “disruptive” technology that exploits natural biological processes for wastewater treatment. Minerals are removed by a secondary processor that uses a combination of forward-osmosis and reverse-osmosis membranes.   During testing the AWP recovered an average of 92% of purified water from wastewater, with maximum performance at 98%. Improvements in average recovery are expected as the technology is matured and as the secondary processor further developed and optimized.

The Alternative Water Processor was developed as a water recovery system capable of recycling wastewater from multiple sources expected in future exploration missions, including hygiene and laundry water, using an innovative, potentially transformational technology based on natural biological processes. The AWP could ultimately replace the functions of the Urine Processor Assembly and reduce or eliminate the need for the multi-filtration beds used in the Water Processor Assembly on the International Space Station (ISS), thus decreasing the need for consumables as compared to the SOA. The AWP was designed to recycle at least 95% of exploration wastewater, including humidity condensate, urine and urine flush, plus hygiene (hand wash, oral, shave and shower) and laundry, whereas the ISS water recovery system only treats humidity condensate, urine and urine flush. In contrast to the ISS WRS, stabilization of the wastewater using harsh and/or toxic chemicals is not required.

At the center of the AWP are two unique “game changing” technologies: 1) a Biological Water Processor (BWP) to mineralize organic forms of carbon and nitrogen; and 2) an advanced membrane processor (Forward Osmosis Secondary Treatment (FOST)) for removal of solids and inorganic ions. At the heart of the BWP are four Membrane Aerated Biological Reactors.

The Alternative Water Processor (AWP) is an integrated biological and physicochemical system. A Biological Water Processor (BWP) composed of a series of four Membrane-Aerated Biological Reactors (MABRs) exploits naturally occurring microorganisms to mineralize organic forms of carbon and nitrogen in the wastewater.  The MABRs  are targeted to remove as much as 90% of the organics, stabilize pH, and convert NH₄⁺ to NO_x^- (up to 80%) then to N₂.   Inorganic ions and suspended solids within the effluent of the BWP are removed by the Forward Osmosis Secondary Treatment (FOST) subsystem. The FOST, an off shoot of Direct Osmotic Concentration, is a membrane processor that uses a combination of Forward Osmosis (FO) and Reverse Osmosis (RO) in series and can easily tolerate wastewaters high in non-volatile organic content and solids associated with shower and/or hand washing, which tend to foul conventional pressure-driven membrane systems.  The FOST approach incorporates FO pretreatment which allows conventional RO to be used to reject these contaminants effectively without premature fouling due to micellar surfactant aggregates.