Nitrogen Recovery Using a New Generation MaX+ Anammox Reactor for Urine Treatment

Sustainable space habitation systems must maintain operations without depending on regular resupply of materials. Wastewater recycling can facilitate sustainable habitation by reducing resupply costs. Biological treatment has previously been shown to be a promising technology to reduce resupply costs compared to only physical/chemical treatment systems. To date most research has evaluated biological reactors that oxidize organic carbon and nitrogen with or without denitrification. These systems can remove >90% of the organic carbon, oxidize ~50-60% of the organic nitrogen but can only remove ~ 50% of the oxidized N due to carbon limitations. A new process, anaerobic ammonium oxidation (Anammox), which can convert >90% of the total N to N2 gas has been demonstrated for treatment of urine. This work evaluates a new generation of these reactors designed to allow for greater volumetric reaction rates and more robust performance. The MaX+ represents a simpler design for Anammox application compared to the previous PaX and MaX reactor. The MaX+ reactor was able to treat a biologically pretreated 1 crew-d urine load (~2L/day). Conversion rates approached 83 g-N/m3-d. Over 91 % of the total N was converted to N2 gas, the equivalent of 7.7 g-N/crew-day or ~7L-N2/crew-day. Results suggest that the MaX+ Anammox system may allow for nearly complete N recovery to a useful end product N2, reducing resupply costs and providing an effluent that can be more easily desalinated without chemical pretreatment.