Electrochemical Deionization of Waste Water Using a New Polymer Membrane Cell 972427

Water is the single largest resource required for crew sustenance during long-term human space missions. To preserve this resource, water must be reclaimed from waste streams containing minimum concentrations of organic and inorganic impurities. The removal of dissolved ions from waste water is essential to regenerative water reclamation technology for life support systems. The aim of this project was to demonstrate a novel electrochemically driven purification method using tubulated bipolar ion exchange membranes for the separation of dissolved ionic impurities from spacecraft waste water. Generally, electrochemical separation methods have limited applications since they can only be applied to the purification of the water that has a sufficiently high dissolved ion content to make the solution conductive. The new method, however, uses a membrane composed of bilayers of oppositely charged ionically conducting polymers. This membrane makes it practical to treat all types of waste water, independently of the water's conductivity. Electricity is the only additional consumable required for this method. Greater than 90% water recovery is possible, depending on the concentration of contaminants in the feed stream. This paper will describe performance tests showing that both inorganic and organic ion impurities in Ersatz solutions could be reduced to 1 part per million or below. The size, weight and power requirements as well as the operation of a continuous flow system will be discussed. The test results provide a technical foundation for further development and scale up for applications in advanced life support systems.