An Assessment of the Water Extraction Capabilities of the Heat Melt Compactor

The Heat Melt Compactor (HMC), a waste management technology developed at the NASA Ames Research Center, was designed to process waste generated aboard spacecraft. The device compacts, encapsulates and sterilizes the waste in preparation for onboard storage. In addition, the unit removes and recovers water, which is ultimately recycled1, rendering the encapsulated waste inhospitable to microbial contaminants. Initial studies indicate that the HMC is capable of removing and capturing 90 to 98% of the water contained in the process waste sample.2 The nineteen experiments conducted at ARC described in this paper attempt to refine, quantify and define the limitations of the Heat Melt Compactor's dewatering and water collection capabilities. The amount of water in the initial waste sample was measured and found to be 19.04% by weight for batches made at ARC and 20.45% for those made at KSC. This was less than the percentage predicted from the standard waste model. The amount of water recovered and collected varied from 12.9 to 98.4% of initial water contained in the waste. For the six tiles tested, the amount of water remaining in the tiles after processing ranged from 6.97 to 37.67%. The water activity for five of these tiles averaged 0.472; all of these issues play a significant role in the survival and propagation of microorganisms. Water activity values below 0.6 inhibit microbial growth. Significant correlation was found to exist between Percent Water Recovery, Percent Expected Water Encapsulated in Tile and Water Activity, the latter two of which are inversely proportional to water recovered. Percent Water Recovery, since it is easily computed, can be used to predict the other two values.