Complete Nitrogen Removal through Integrating Anammox and Autotrophic Denitrification in an UASB Reactor

Complete nitrogen removal was achieved through integrating anammox and autotrophic denitrification in an UASB reactor. The total nitrogen（TN） removal rate increased stepwise from 0.46 to 0.94 kg-N/（m;·d）, with an effluent TN concentration of below 3.0 mg-N/L achieved. The process is relatively insensitive to the nitrite to ammonium ratio, achieving complete nitrogen removal when their ratio in the influent varied in the range of 1.35—1.55. The added S;quantity in the system could be utilized to adjust the competition between autotrophic denitrifiers and anammox bacteria. High-throughput sequencing technology indicated that Candidatus;uenenia and Thiobacillus were the functional strains for anammox and autotrphic denitrification process, respectively, in the studied reactor. This result provides a theoretical and technical basis for the large-scale application of anaerobic ammonium oxidation process.