Next Generation Water Recovery for a Sustainable Closed Loop Living
Authors: Vijapur Santosh H. , Hall Timothy D. , Taylor E. J. , Wang Dan , Snyder Stephen , Cabrera Carlos R , Barreto-Vázquez Delmaliz , Rojas-Pérez Arnulfo 
Published: February 2020

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 earth availability. The existing supply of water on the International Space Station (ISS) is managed by Environmental Control and Life Support System (ECLSS) which recovers and recycles water from human waste. The best estimates available show that this system works at efficiencies between 75% to 85% water recovery which requires relatively frequent refueling to sustain life upon the ISS. As human missions travel further into the solar system the availability of resources to resupply will be diminished due to availability and ease of resupply. Therefore, next-generation systems to recycle water are required to reduce waste and improve system efficiency. Upon a critical evaluation of the existing ECLSS system we find that the water recovery system has lifetime/durability limitations due to inefficiencies within existing process like vapor compression distillation (VCD), reverse and forward osmosis (RO/FO) filtration. Requiring the supply of complex hazardous chemicals to treat these system components such that they maintain their targeted performance.
Within this context, Faraday Technology Inc. and the University of Puerto Rico (UPR) are developing a custom bio-electrochemical 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.
In this talk we will be discussing the ongoing developments at Faraday. Where we have developed a custom bench-scale ammonia reactor and confirmed that the reactor can oxidize ammonia from basic electrolytes. Further, the ammonia reactor was used to demonstrate the potential of oxidizing ammonia utilizing near neutral urine simulants. These results are promising and an early indication that the bio-electrochemical system will be able to operate with high performance efficiency. We are continuing the technology development efforts by (1) leveraging existing knowledge to design and test the bio-electrochemical reactor under zero gravity conditions; (2) exploring the efficacy of (P. Vulgaris) bacteria for urea bioreactor, (3) evaluating electrocatalyst for ammonia oxidation reactor, (4) optimizing the electrocatalytic efficiency and waste water treatment rate with urine simulants, (5) validating operation under zero gravity conditions; and (6) designing and building a demonstration-scale bio-electrochemical reactor unit capable of meeting NASA required specifications.

Acknowledgements: The financial support of NASA Contract No. NNX17CA30P and 80NSSC18C0222 is acknowledged.