Long‐term addition of micro‐amounts of hydrazine enhances nitrogen removal and reduces <scp>NO</scp> and <scp>NO₃</scp>⁻ production in a <scp>SBR</scp> performing Anammox

Abstract

Abstract BACKGROUND N 2 H 4 and NO are the important intermediates of Anammox. The appropriate addition of N 2 H 4 weakens the inhibitory effect of NO 2 − on anaerobic ammonium oxidation bacteria ( AnAOB ) activity. The effect of long‐term addition of micro‐amounts of N 2 H 4 was investigated in this study. RESULTS A sequencing batch reactor ( SBR ) performing Anammox could run stably during long‐term addition of micro‐amounts of N 2 H 4 . The nitrogen removal rate and efficiency of the SBR with micro‐amounts of N 2 H 4 addition were higher than the SBR without N 2 H 4 addition. The molar ratio of NO 3 − production to NH 4 + removal ( MRNN ) decreased to 0.12, significantly lower than the expected stoichiometry of Anammox. The NO emission decreased by more than 15%. The addition of micro‐amounts of N 2 H 4 could weaken the inhibition of NO 2 − to the activity of AnAOB . CONCLUSION The electrons released from the oxidation of added N 2 H 4 by AnAOB acclimated under long‐term micro‐amounts of N 2 H 4 addition replenish the loss of electrons due to the diffusive loss of intermediates in AnAOB metabolism, enhance the activity of AnAOB and accelerate the NO consumption with resulting decreased NO emission. The oxidation of added N 2 H 4 partially substitutes the oxidation of NO 2 − to NO 3 − for the anabolism of AnAOB with resulting significantly decreased production of NO 3 − .© 2014 Society of Chemical Industry