Removal of Urea and Ammonia from Real Human Urine using Bio-electrochemical Reactor system for Closed Loop Environments.

Water recycling system with improved efficiencies to satisfy the water demand in a closed loop environment is required by NASA's Environmental Control and Life Support Systems (ECLSS). Wastewater recycling system in the ECLSS has a water reclamation efficiency limitation of approximately 90%. Therefore, next-generation technologies are required to improve the ECLSS in spacecraft and future planetary space stations for the Moon or Mars. Accordingly, the University of Puerto Rico, in collaboration with Faraday Technology, are developing a sustainable continuous bio-electrochemical process for urea and ammonia removal from wastewater. that will aid the water reclamation process by limiting precipitation events that result from the presence of urea in the urine. This approach will convert the urea to ammonia in a continuous enzyme-based bioreactor, then the bioreactor effluent will travel through an electrochemical oxidation reactor where the ammonia would be oxidized to H2 and N2.

The bioreactor uses P. vulgaris microbial enzyme that consumes the urea, through urease catalyzed hydrolysis. Urease hydrolysis generates an ammonia rich bioreactor effluent that can be electrochemically treated . Our work has demonstrated that the resulting effluent from the bio-electrochemical system has significantly reduced ammonia and urea concentration, when testing synthetic urine feed streams. Furthermore, the semi-continuous operation of the bio-electrochemical system has been validated during a zero-gravity parabolic loop flight test flown in May 2021.

Recently, the bio-electrochemical system was evaluated with real human urine, and we intend to report those results at ICES. Overall, this project demonstrates the potential of a bio-electrochemical system that can improve the lifetime and durability of the water recovery system used in closed loop living environments.

Acknowledgements: This project is partially supported by the National Aeronautics and Space Administration (NASA) Training Grant No. NNX15AI11H. Also, NASA Contract NNX17CA30P, 80NSSC18C0222.