Water Recovery from Wastes in Space Habitats-a Comparative Evaluation of SBIR Prototypes

Water is of critical importance to space missions due to crew needs and the cost of supply. To control mission costs, it is essential to recycle water from all available wastes - both solids and liquids. Water recovery from liquid water wastes has already been accomplished on space missions. For instance, a Water Recycling System (WRS) is currently operational on the International Space Station (ISS). It recovers water from urine and humidity condensate and processes it to potable water specifications. However, there is more recoverable water in solid wastes such as uneaten food, wet trash, feces, paper and packaging material, and brine. Previous studies have established the feasibility of obtaining a considerable amount of water and oxygen from these wastes (Pisharody et al, 2002; Fisher et al, 2008; Wignarajah et al, 2008). This paper summarizes the results of laboratory studies that were conducted to recover water from solid wastes using hardware developed via Small Business Innovative Research (SBIR) grants. The SBIR hardware included a microwave powered freeze drying unit, a microwave powered ambient pressure dryer, and a recirculating hot air dryer. The results are presented and the advantages and disadvantages of each of these technologies are discussed in relation to the potential applications of these units for recovery of water from solid wastes on space missions.