Autotrophic ammonia removal in anaerobic membrane bioreactor and moving bed biofilm reactor

Abstract

Biological nitrogen removal (BNR) from effluents conventionally achieved by combined autotrophic nitrification and heterotrophic denitrification is energy intensive and results in high production of sludge. Advanced BNR processes based on single and combined autotrophic processes such as Anaerobic Ammonium Oxidation (ANAMMOX), and Complete Autotrophic Nitrogen removal Over Nitrite (CANON) achieved through partial autotrophic oxidation of NH4 +-N to NO2 --N yields about 25 % energy savings and 40 % savings on organic carbon addition. The feasibility of developing an Anaerobic Membrane Bioreactor (AnMBR) for startup and stabilization of ANAMMOX process and Moving bed biofilm reactor (MBBR) for CANON process for the treatment of nitrogenous effluents with low organic load is the focus of this research. The objective of the research was to evaluate the performance of AnMBR and MBBR for autotrophic ammonia removal from nitrogen rich wastewater with low organic load. It was initiated by enriching ANAMMOX populations from seeds of anaerobic (vegetable waste digester and biosolids digester) and aerobic origin (activated sludge process from a sewage treatment plant (STP)). The study revealed that ANAMMOX populations could be successfully enriched from anaerobic and aerobic seeds under anoxic conditions with NH4Cl/NaNO2 ratio (1:1). Anaerobic seed from biosolids digester is better (99 % NH4 +-N removal efficiency) compared to anaerobic seed from vegetable waste digester (90 98 % NH4 +-N removal efficiency) and aerobic seed (87 93 % NH4 +-N removal efficiency) for ANAMMOX enrichment. The AOB sequences were closely related to Nitrosomonas europaea and N. communis and the NOBs were related to Nitrospira spp. and Nitrobacter spp. The doubling time (td) of ANAMMOX bacteria achieved was 9.8 d during CANON startup process and 7.5 d during CANON optimization process, as compared to td of 11 to 14 d reported in literature. newline newline newline