Next Generation Water Recovery for a Sustainable Closed Loop Living

Abstract

In order to facilitate extended human space travel, solutions and innovations are required to enable habitation in microgravity spacecraft habitats such as International space station (ISS), with limited supply availability. At present, the Environmental Control and Life Support System (ECLSS) within the ISS recovers and recycles 90% of the water from human waste. However, their efficiency decreases during their lifetime owing to unmanageable process contaminants, requiring ground support to supply complex hazardous chemicals to treat these system components such that they maintain their targeted performance[i] ,[ii],[iii]. As human missions travel further into the solar system, the availability of ground support will be diminished. Therefore, next-generation systems to recycle water are required to reduce waste and improve system efficiency. Within this context, Faraday Technology Inc. and the University of Puerto Rico (UPR) are developing a bio-electrochemical waste water treatment system. Within this system, a bioreactor will convert urea from the waste water to ammonia by hydrolysis:NH2(CO)NH2 + H2O → 2NH3 + CO2 (1)Next the effluent of the bioreactor will flow through the ammonia oxidation reactor:2NH3 → N2 + 3H2 (2)Thus, generating urea free waste water effluent for further filtration and enhancement. The developed technology has the potential to be compatible with existing ECLSS systems and be an integral part of the closed loop living systems required for long term life support on NASA’s manned space missions.Ongoing activity between Faraday Technology and UPR has demonstrated an 85% conversion of urea to ammonia in a bioreactor and a near complete conversion of ammonia in an electrochemical reactor in a laboratory set-up utilizing a synthetic urine electrolyte[iv] ,[v]. Based on the studies, Faraday has designed and built an alpha scale reactor to process 6 L volume of urine per day as per NASA specifications. The next step in reactor demonstration activities is to understand the effects of zero-gravity on the ammonia reactor. The electrochemical reactor and components are assembled in an electrochemical microgravity laboratory setup (Figure 1). Optimized conditions from ground-based performance data will be implemented during the zero-gravity flight test to evaluate the feasibility of ammonia oxidation in zero-gravity environment. The flight test is scheduled for May 2021.In this talk we will be discussing the ongoing developments at Faraday, where we have (1) leveraged existing knowledge to design and test the bio-electrochemical reactor under zero gravity conditions; (2) evaluated electrocatalyst for ammonia oxidation reactor; (3) optimized the electrocatalytic efficiency and waste water treatment rate with urine simulants; (4) designed and built a demonstration-scale bio-electrochemical reactor unit capable of meeting NASA required specifications; and (5) will be validating operation under zero gravity conditions during the May 2021 zero gravity test flight. Acknowledgements: The financial support o...