In order to facilitate human space travel, solutions and innovations are required for supporting the efficient maintenance of water, closed air, and waste systems in spacecraft habitats that operate on planetary environments. As missions are foreseen to be extended with limited earth resupply available there is need to develop durable and sustainable closed loop living systems. Waste water treatment and recovery system that is managed by Environmental Control and Life Support System (ECLSS) on board the International space station (ISS) is one such system that has lifetime/durability limitations and would benefit from improvements to increase its lifetime efficiency. Current systems typically recover about 85% of the water with a marked process efficiency decrease throughout the lifetime of the systems use due to incoming process contaminants. Typical water contaminants commonly enter the ECLSS through the waste water from the onboard team members and contain complex molecules that tend to foul and reduce the efficiency of the reverse osmosis (RO) systems^[1],[2]. Therefore, in order for manned deep space missions to be practical it is critical to create state of the art durable and efficient processes to reduce the impact of contaminants on the waste water system efficiency.

Within this context, Faraday Technology Inc. and the University of Puerto Rico (UPR) are working on developing a technology to eliminate many of the contaminants that commonly foul the RO system and produce a more durable closed loop wastewater treatment and water recovery system as demonstrated in Figure 1[3]^,[4]. At Faraday Technology Inc., we develop a custom bench-scale ammonia electrolyzer with Pt coated electrodes fabricated by the FARADAYIC^®[5] Process. The developed catalysts and electrolyzer are used to evaluate ammonia oxidation for wastewater treatment as following reactions:

The influent ammonia from waste water can be oxidized in an electrolyzer according to the reaction:

2NH₃ + 6OH^- → N₂ + 6H₂O + 6e^- (1)

while water is simultaneously reduced according to the following reaction:

6H₂O + 6e^- → 3H₂ + 6OH^- (2)

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.

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

[1] H. K. Shon, S. Vigneswaran, I. S. Kim, J. Cho, H. H. Ngo “Effect of pretreatment on the fouling of

membranes: application in biologically treated sewage effluent”. J. Membr. Sci. 2004, 234 (1-2), 111-120.

[2] S. Q. Zou, Z. He “Enhancing wastewater reuse by forward osmosis with self-diluted commercial fertilizers as draw solutes”. Water Res. 2016, 99, 235-243.

[3] E. Nicolau, J. J. Fonseca, J. A. Rodriguez-Martinez, T. M. J. Richardson, M. Flynn, K. Griebenow, C. R. Cabrera “Evaluation of a Urea Bioelectrochemical System for Wastewater Treatment Processes”. ACS Sustainable Chemistry & Engineering 2014, 2 (4), 749-754.

[4] C. R. Cabrera, F. A. Miranda, “Advanced Nanomaterials for Aerospace Applications”. Chapter 1. Pan

Stanford Publishing Pte. Ltd., Singapore 2014.

[5] FARADAYIC^® is a registered service mark (Reg. No. 3,423,999 5/6/2008) of Faraday Technology.