Improvements in brine water recovery are critical to advancing NASA’s goals for human exploration of space. Water recovery systems must minimize the need for new supplies of clean water by closing the water loop. To accomplish this, water losses must be minimized or eliminated. A major loss of water is the brine produced by the primary water processor. For current technologies, this loss can be up to 15%.
A novel brine dewatering system, referred to as Brine Residual in Containment (BRIC), has been developed. BRIC aims to minimize system complexity and increase the robustness and efficiency of the dewatering system design by effecting brine drying inside the container used for final disposal. The design concept considers strategies for the broad range of mission scenarios now being considered for human space flight, including capabilities for achieving total water recovery and microgravity compatibility.
The novelty of BRIC lies in effecting reduced complexity in the evaporator design while still accommodating all three phases of state associated with the brine dewatering process: liquid, vapor, and solid. This is done by drying brine inside the container used for final disposal. A related “in-place” drying process was developed for the nuclear waste industry to reduce storage volume and minimize contact with solids from radioactive wastewater. The in-place drying and disposal concept offers several potential advantages for brine drying on spacecraft. First, high water recovery rates are potentially achievable without the need to incorporate special design considerations to mechanically transport the solid dewatered brine material. Second, drying within the disposal container offers a means to limit crew exposure to dewatered brine solids. Sealing the used container, and removing and replacing it, can be automated to further limit crew exposure. Third, the design allows for direct heating of the brine, which can increase drying efficiency and minimize the potential for fouling of heat transfer surfaces. A fourth potential advantage of the in-place solids disposal concept is the reduced number of design elements and moving parts required, which could increase the overall robustness and efficiency of the system. Finally, the various design elements of the concept, if required, may be amenable to strategies for accomplishing microgravity compatibility.
BRIC incorporates several uniquely conceived design solutions into a novel brine dewatering system. The unique design solutions include an evaporative drum with a disposal solids collection chamber, vacuum-assisted thin-film drying processes, direct heat transfer methods, and consideration and strategies to help achieve microgravity compatibility. These design solutions are aimed at meeting a broad set of specialized requirements to effect high degrees of water recovery that may be broadly applicable to a wide variety of complex concentrated wastewater solutions. Recent test results of the pre-prototype system using concentrated brine have demonstrated total water recovery approaching 99%.
This work was done by Michael Callahan, Michael Casteel, and David Glock of Johnson Space Center. For further information, contact the JSC Innovation Partnerships Office at (281) 483-3809. MSC-24964-1