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The recovery of important minerals, salt (NaCI) and potassium (K), in a closed system, namely CELSS is discussed. NaCI is needed for humans, but is potentially harmful to plants. Salt is recovered after wet oxidation of urine. Since Na and K have similar chemical and physical properties, their recovery or separation may require sophisticated methods. Na, CI and K ions are separated from other ions by electrodialysis with univalent selective ion-exchange membranes and then NaCI is obtained separately by a crystalization process. Preliminary experiment on crystalization of NaCI-KCl mixed solutions showed a good separation result.

A conceptual model of a life support system which circulates material using a physicochemical treatment has been designed. This self-contained partially circulated life support system, called SEPAL, comprises a water electrolysis system using a PEM (Polymer Electrolysis Membrane) and solar collector for a Sabatier reactor. The lack of buoyancy in microgravity causes liquid-gas separation and interferes with conventional water electrolysis. This problem can be solved by supplying water in the vapor phase through molecule size pores in the NAFION electrolysis membrane. This new system connects to a Sabatier reactor, which provides the water vapor for the electrolysis system. This paper describes test results of the main system elements and preliminary test results of the oxygen and hydrogen production system. With a small satellite making use of surplus lifting capacity, the experiment is proposed to demonstrate this circulated life support system.

Conceptual studies of closed ecological life support systems (CELSS) carried out at NAL in Japan for a water recycle system using membranes1) are reviewed. The system will treat water from shower room, urine, impure condensation from gas recycle system, and so on. The H2 O recycle system is composed of pre-filter, ultrafiltration membrane, reverse osmosis membrane, and distillator. Some results are shown for a bullet train of toilet-flushing water recycle equipment with an ultrafiltration membrane module. The constant value of the permeation rate with a 4.7m2 of module is about 70 1/h after 500h of operation. Thermovaporization with porous polytetrafluorocarbon membrane is also proposed to replace the distillator.