Autotrophic ammonia removal from landfill leachate in anaerobic membrane bioreactor

Anaerobic ammonium oxidation (ANAMMOX) process, an advanced biological nitrogen removal, removes ammonia using nitrite as the electron acceptor without oxygen. In this paper, ANAMMOX process was adopted for removing -N from landfill leachate having low COD using anaerobic membrane bioreactor (AnMBR). The AnMBR was optimized for nitrogen loading rate (NLR) varying from 0.025 to 5kg -N/m(3)/d with hydraulic retention time (HRT) ranging from 1 to 3d. -N removal efficacy of 85.13 +/- 9.67% with the mean nitrogen removal rate of 5.54 +/- 0.63kg -N/m(3)/d was achieved with NLR of 6.51 +/- 0.20kg -N/m(3)/d at 1.5d HRT. The nitrogen transformation intermediates in the form of hydrazine (N2H4) and hydroxylamine (NH2OH) were 0.008 +/- 0.005 and 0.006 +/- 0.001mg/l, respectively, indicating co-existence of aerobic ammonia oxidizers and ANAMMOX. The free ammonia (NH3) and free nitrous acid (HNO2) concentrations were 26.61 +/- 16.54mg/l and (1.66 +/- 0.95)x10(-5)mg/l, preventing -N oxidation to -N enabling sustained -N removal.