Several biological systems have been investigated for treatment of space wastewater, with considerable success. Texas Tech University (TTU) has experimented with variations on a membrane-aerated bioreactor since 2002. Its most recent iteration, the rCOMANDR unit, is an aerobic process which treats space wastewater at a rate equivalent to that produced by 2 crew/day, achieving >50% conversion of organic nitrogen to NO2 and NO3 (NOx) and >85% removal of dissolved organic carbon (DOC), with ~90% of NOx in the form of nitrite. Effluent NH3-N:NO2-N is typically near 1:1. Pancopia has developed an alternative approach using a consortium of aerobic Nitrifiers with anaerobic Denitrifiers and anammoX (NDX), which was successful in removing 85% of ammonia and carbon. A key element in this system, the anammox bacteria, oxidizes ammonia with nitrite at a 1:1.3 ratio to produce N2 gas, allowing the removal of nitrogen without oxygen or organic carbon requirement. This enables a greater overall removal of nitrogen in typically carbon-limited space wastewaters.
As the focus of this Phase 1 SBIR, Pancopia proposes investigating the feasibility of a second-stage anammox reactor to remove most of remaining ammonia and nitrite from rCOMANDR effluent.
Phase 1 criterion for assessing the feasibility of the proposed second-stage anammox process for removal of ammonia and nitrite is an average removal of more than 50% of ammonia and nitrite from rCOMANDR effluent in two of the three test reactors during the 4-week test period.