Catalytic Oxidation for Treatment of ECLSS & PMMS Waste Streams, 1991 911539
The sorption and ion exchange water reclamation technologies used to treat the waste streams in the Environmental Control and Life Support System (ECLSS) and Process Materials Management System (PMMS) are ineffective for removal of low molecular weight, polar organic contaminants which do not have ionized forms. These include likely waste stream constituents such as methanol, ethanol, isopropanol, and acetone. Catalytic oxidation of these compounds in oxygen saturated water at moderate temperatures (125 to 160 C) provides a reliable, simple, and inexpensive way to eliminate these contaminants. By the suitable choice of catalysts, these species can be converted to carbon dioxide and water or to species which can be removed effectively by sorbents and ion exchange resins. The operation requirements of the baseline system are oxygen and heat. Since much of the heat is recovered, the energy use of the technology is very low. In the current gravity independent configuration, membrane oxygen saturators and carbon dioxide degassing units deliver the oxygen and remove the reaction byproducts. This prototype system has the demonstrated capability to lower 50 ppm ethanol levels to the part per billion level after catalyst contact times of 1 to 3 minutes. In addition, at slightly longer contact times a solution containing alcohols and acetone can be oxidized lowering these trace contaminants from 34 ppm to less than 500 ppb. Similar catalysts have also shown effectiveness at removing chlorinated organics such as chloroform and trichloroethylene from urine distillates pretreated with oxidizing compounds.