Evaluation of Aquaporin Membranes Using ISS Humidity Condensate Ersatz Wastewater

On the International Space Station (ISS), distillate from the Urine Processor Assembly (UPA) and humidity condensate from the cabin are processed through a sequence of operations including distillation, filtration, adsorption, ion exchange, and catalytic oxidation. The use of adsorption and ion exchange beds in the Water Processor Assembly (WPA) are one of the main contributors to the resupply mass requirement. Developing improvements to the multifiltration system in order to reduce or eliminate the usage rate of expendable media such as adsorbents and ion-exchange resins is an important part of the evolution of ISS systems for future exploration missions. Development of the ISS Multifiltration Bed Replacement (MFBR) technology is based on a new generation of biomimetic membranes derive their unique characteristics from a protein call an Aquaporin. These membranes are capable of rejecting many semi-volatile organic compounds and were recently commercialized by the company Aquaporin A/S. NASA has conducted several studies on the use of Aquaporin membranes for the rejection of total organic carbon (TOC) of simulated ISS humidity condensate wastewater. Tests were conducted to determine the maximum water recovery ratio, and TOC rejection for both a flat sheet membrane and a membrane module. The results indicate that the aquaporin membrane can reject a minimum of 50% of the TOC using the simulated ISS humidity condensate ersatz, and achieves product water with a TOC value below 30 ppm.