NASA's Ammonia Recovery System for Wastewater was developed for potential use as part of the Environmental Control and Life Support Systems (ECLSS) on the International Space Station. The system uses an affordable media that is highly selective for ammonia. Ammonia concentrations in wastewater as high as 100,000 ppm can be reduced to less than 1 ppm. ECLSS conditions require low power usage, and the avoidance of high-temperature and high-pressure operations. The state-of-the-art for ammonia removal involves biological processes or ion exchange, and neither of these meets NASA's ammonia capture/recovery needs. Biological processes have high complexity, high volume requirements, and introduce contaminants in the effluent. Ion exchange is not very selective for ammonia, and requires regeneration, which requires large amounts of consumables and produces impure ammonia.
An ammonia capture/recovery system for wastewater was developed for use on the International Space Station with potential for larger industrial and municipal wastewater needs. Following treatment, the media is economically regenerated for reuse in the system, and aqueous ammonia is captured as a byproduct. This system has three primary functions: removal of ammonia from wastewater using a magnesium-based media, which is converted to the ammonia form; capture of the ammonia for later use (e.g., as a fertilizer); and regeneration of the capture media for reuse in the system (i.e. the ammonia form is converted back into the magnesium-based media).
The system provides higher capacity than traditional absorbents (multiple equivalents ammonia/L substrate). It is also effective under varying influent ammonia concentrations (e.g., from 10s to 100,000s of ppm ammonia). Contact time of 20 to 30 minutes is needed for complete removal, with similar times needed for regeneration. Ammonia is captured/recovered during the media regeneration phase (ammonia can then be reused or sold).