Analysis of Candidate Technologies for a Partial Gravity Water Recovery System
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The development of a Partial Gravity Water Recovery System (PGWRS) for a future long-duration mission to a lunar/planetary surface is an unmet need. The Water Recovery System currently used aboard the ISS recovers potable water from urine, flush water, and humidity condensate and necessarily employs microgravity-compatible technologies. A PGWRS, in comparison, is amenable to the inclusion of more reliable gravity-based separation techniques and may additionally be required to process hygiene and laundry wastewaters. Here, we discuss the anticipated compositions and flow rates of the types of wastewaters expected to be produced on an early planetary base, the general structure of a water recovery architecture capable of taking such waste streams to potable quality, and several different candidate technologies that can fulfill one or more processing functions. Additionally, we present a mathematical model of a Membrane Aerated Bioreactor (MABR) - Reverse Osmosis (RO) system that was used in trading four different simple water recovery architectures, each accommodating either a mixed waste stream or two segregated waste streams and featuring an RO system in either an internal recycle or MABR recycle configuration. Our analysis results suggest that the architecture masses are sensitive to certain parameters, such as the RO recovery fraction, with each of the four configurations being potentially lucrative under the appropriate set of operating conditions. Finally, we identify knowledge gaps for promising technologies that arose during our analysis and that we recommend closing via future modeling and/or testing efforts.