Plasma-Based water purification for crewed space missions: Laboratory experimental comparisons for on-board applicability

Abstract

Low-temperature, atmospheric pressure plasma presents a new, inexpensive, and environmentally friendly method of water purification. For long duration crewed space missions, a novel water purification system that does not rely on consumable filters and chemicals would be desirable. Plasma systems provide a viable option for these missions, but their operation and designs need to be optimized and compared to existing technology. For this application, gas and power usage are key limiting factors. In this work, water contaminated with methylene blue is purified with plasma. The rate of purification, gas flow usage, and power consumption are compared for multiple devices. A single atmospheric pressure plasma jet is compared with jet array configurations and a novel, 3D printed “plasma sheet” design that expands the size of the plasma surface area. A resource gauge parameter was developed to compare the resource usage and purification rate of each device, and this parameter showed that the plasma sheet was able to improve the rate of purification without increasing resource usage. Additionally, two types of jet arrays were designed that demonstrated the need to exceed a minimum energy and flow rate threshold to maintain effective treatment. A low cost jet was also developed that showed suitable treatment results with a two order of magnitude cost reduction. Finally, a figure of merit was discussed to compare the best performing plasma device with the urine processor assembly used on the International Space Station.