Response of nitrogen removal and microbial community to high concentration of humic acid in the anammox biofilm system

The anaerobic ammonium oxidation (anammox) process is highly effective to remove nitrogen from the wastewater with high ammonia concentration, such as landfill leachate and anaerobic digestion. This kind of wastewater generally contains high content of humic acid, and its effect on anammox is not clear. Therefore, this study investigated the effect of humic acid with high concentration (100–1000 mg/L) on the anammox biofilm system. The nitrogen degradation rates were greatly decreased at the high concentration of humic acid and the reaction time was prolonged by 4 h compared with that lacking humic acid. In the anammox biofilm system, the relative abundance of anammox bacteria Candidatus_Brocadia and Candidatus_Kuenenia decreased from 2.1 % and 15.01 % to 0.6 % and 8.32 %, respectively, while the denitrifying bacteria Thauera increased from zero to 8.86 %. Overall, the high humic acid concentration did not obviously inhibit nitrogen removal performance of anammox system, but affected anammox bacteria activity and microbial community structure.