Population Dynamics of Aerobic and Anaerobic Ammonia Oxidizers in an Autotrophic Nitrogen Removal Membrane Biofilm Reactor

This work presents an application of a hollow-fiber membrane-aerated biofilm reactor (HFMBR) to couple partial nitrification with anaerobic ammonia oxidation (anammox). For 18 months the HFMBR treated an ammonium-based, organic carbon-free synthetic wastewater designed to mimic a high-strength nitrogen waste such as a source-separated urine waste stream. After rapid startup of nitritation, nitrite-oxidation was observed but controlled by limiting the ratio of the oxygen to the ammonium flux. Analysis of microbial populations using fluorescence in situ hybridization (FISH) revealed few significant trends with respect to distance along the membrane fibers, but fibers exposed by sloughing created aerobic niche environments favorable for NOB colonization. After 300 days, anammox activity was inferred from reactor performance, prior to detection of a population by molecular methods. Total nitrogen removal averaged 74% ± 6.2% for the subsequent 250 days of operation.