Feasibility of UV LEDs in a Spacecraft Wastewater Application: Exploring Biofilm Control in the WPA Wastewater Tank

As the National Aeronautics and Space Administration (NASA) expands its scope and begins to venture into long-duration, manned space flights, the function and maintenance of spacecraft water systems becomes increasingly critical and difficult to achieve. New mission requirements will limit opportunities for resupply and demand extended periods of uncrewed operations. Based on lessons learned from the International Space Station (ISS), one particular challenge of future spacecraft water systems will be maintaining adequate microbial control, especially in water subsystems and component-level elements where effective long-duration biocontrol strategies do not currently exist. To ensure the reliability and redundancy in these systems, new technologies will be needed in order to ensure mission success. After proving feasibility of commercial off-the-shelf (COTS) ultraviolet (UV) light emitting diodes (LEDs) disinfection devices in flow through applications in 2018, our current work has focused on the development of UV LED technology for microbial control in bellows-style spacecraft wastewater tank. Two primary strategies were developed used to determine initial feasibility. The strategies included, (1) flow into, continuous recirculation, and flow out of the tank volume through a standalone UV reactor system, and (2) direct UV irradiation on the wetted tank surfaces using an integrated UV-tank array. This paper summarizes the feasibility of these approaches through benchtop and subscale tank testing and outlines the proposed development pathway of these technologies for biofilm control in a wastewater tank applications.