Advanced Air Evaporation System with Reusable Wicks for Water Recovery

Abstract

Water contained in brine is critical to water loop closure during future extended manned space missions where resupply logistics become increasingly prohibitive beyond earth orbit. Current primary water processes recover greater than 90% of the water in wastewater and produce highly contaminated brine. Additional water recovery has been limited by the high level of solids in urine, one of the largest wastewater sources, because inorganic solids reach saturation levels and precipitate while organic solids tend to form sticky pastes that foul equipment and impede water removal. This paper describes a microgravity-compatible Advanced Air Evaporation System (AAES) for reclaiming nearly 100% of water from brine without concern for these solids. This novel approach utilizes hydrophilic ceramic fabrics, felts, or fibers as a refractory wicking material. Water is evaporated from brine-saturated ceramic wicks in a drying chamber resulting in the recovery of water vapor by condensation while brine solids accumulate on ceramic wicks. Several sub-processes are utilized to regenerate these wicks. After each drying cycle, organic solids are removed by thermal oxidation leaving inorganic salts on the wick. Additional brine may then be processed using the partially regenerated wick. Following several oxidation cycles, inorganic salts are removed by elutriation with water forming a saturated salt solution and a fully regenerated wick. This initial two-step regeneration cycle recovers 78% of the water from the brine with the remaining water forming the salt solution. Recovery of the remaining water from the salt solution without the presence of organic solids is a straightforward process and the resultant overall water recovery will approach 100%. Future development of the AAES will enable increased water recovery, reduced resupply logistics, improved reliability, and lowered Equivalent System Mass (ESM) for water recycling during future space missions.