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A single cell electrochemical reactor that utilizes a proton exchange membrane (PEM) as a solid electrolyte is being investigated and developed at Texas A&M University for post-treatment of reclaimed waters with low or negligible electrolyte content. Post-treatment is a final polishing of reclaimed waste waters prior to reuse and constitutes removing organic impurities at levels as high as 100 ppm to <500 ppb total organic carbon (TOC) content and provides disinfection. The system does not utilize or produce either expendable hardware components or chemicals and has no moving parts. This paper discusses a single cell reactor concept; test system design; the role of the proton exchange membrane; and the principle of organic impurity oxidation at PEM interfacial reaction zones. The fabrication performance evaluation; design and sizing of a prototype system are discussed. Test data and kinetic analysis are presented.

An aqueous phase catalytic oxidation system (APCOS) was designed, tested and delivered to NASA/Johnson Space Center (JSC). The APCOS removes residual organic impurities in reclaimed water to a level acceptable for potable use and to provide disinfection. The reactor, which contains a heterogeneous catalyst consisting of a noble metal on an inert support medium, operates at 120 - 150 °C and at fluid pressures of several atmospheres to maintain an aqueous liquid phase. Pressurized gaseous oxygen, used as the oxidant, is directly injected into the liquid phase. A description of the subsystems process hardware is presented. The APCOS was demonstrated to mineralize organic impurities at concentrations of 100 mg/L total organic carbon (TOC) to < .5 mg/L (<500 μg/L TOC). In addition, disinfection features were demonstrated with microbial challenge tests.

This paper addresses the derivation of chemical ersatz recipes for use in the evaluation of development hardware designed for advanced spacecraft water recovery systems. The recipes simulate characteristics of wastewater generated on a transit mission and on an early planetary base (EPB). In addition, recipes are provided which simulate the water quality of the early planetary base wastewater as it moves through a combination biological and physical-chemical water recovery system. These ersatz are considered to be accurate representations of the wastewater as it passes through primary, secondary, and tertiary processing stages. The EPB ersatz formulas are based on chemical analyses of an integrated water recovery system performance test that was conducted over a period of one year. The major inorganic and organic chemical impurities in the raw wastewater, and in the effluent from the various subsystems, were identified and quantified.

A microgravity whole body shower and waste water recovery system were evaluated in three separate closed loop tests at NASA/JSC. These tests covered a period from August 1985 to June 1987 in which shower waste water was reclaimed and reused for showering. Test persons showered in a preprototype whole body shower following a protocol similar to that anticipated for the Space Station. Each test was performed by using different water recovery system technologies which included phase change distillation and two separate reverse osmosis processes. These were integrated with post-treatment for the final purification of the reclaimed water. The phase change, a preprototype Thermoelectric Hollow Fiber Membrane Evaporation Subsystem was used for the initial test with chemical pretreatment of the shower waste water input. A reverse osmosis dynamic membrane system was used for the second test and a 2-stage ultrafiltration/reverse osmosis system for the third test.

A microgravity whole body shower (WBS) and a waste water recovery system (WWRS) were used in a closed loop test at the Johnson Space Center. The WWRS process involved chemical pretreatment, phase change distillation and post-treatment. A preprototype Thermoelectric Integrated Hollow Fiber Membrane Evaporation Subsystem (TIMES) was used for distillation after pretreatment and the post-treatment was accomplished with activated carbon, mixed ion exchange resin beds and microbial check valve (MCV) iodine bactericide dispensing units. The purposes of this test were to evaluate a NASA approved Shuttle soap for whole body showering comfort; evaluate the effects of the shower water on the WBS and the TIMES; and evaluate purification qualities of the recovered water in a closed loop operation.

This paper discusses the recent developments in water quality monitoring for Space Station reclaimed wastewaters. A preprototype unit that contains an ultraviolet absorbance organic carbon monitor integrated with pH and conductivity sensors is presented. The preprototype has provisions for automated operation and is a reagentless flow-through system without any gas/liquid interfaces. The organic carbon monitor detects by ultraviolet absorbance the organic impurities in reclaimed wastewater which may be correlated to the organic carbon content of the water. A comparison of the preprototype organic carbon detection values with actual total organic carbon measurements is presented. The electrolyte double junction concept for the pH sensor and fixed electrodes for both the pH and conductivity sensors are discussed. In addition, the development of a reagentless organic carbon analyzer that incorporates ultraviolet oxidation and infrared detection is presented.