The state of the art ECLS technology can efficiently recover water from urine, but fails to adequately address solid waste. This gap must be resolved to close the waste loop and facilitate long duration, sustainable space habitation. "The Marshian" is a conceptual design for an artificial waste treatment wetland tailored for efficient, autonomous, low-maintenance processing of human waste in any setting with sufficient gravity (i.e. Moon or Mars). The design is rooted in the "French Reed Bed" system, a contemporary alternative to municipal waste treatment processing. Through a series of gravity-fed terraces, the Marshian facilitates sediment settlement and leverages microbial and plant metabolisms to reduce BOD and fecal coliforms to safe levels. The use of in-situ resources for construction and operation, along with ecological remediation of said resources, reduces ESM costs to be comparable with physicochemical alternatives. The design incorporates a water retention basin that serves as a naturalistic space for crew members' benefit, and has potential to be optimized for fiber, food, or pharmaceutical production, further increasing the self-sufficiency of a potential colony.
Grove et al. (Sun,) studied this question.