Low maintenance anammox enrichment and nitrogen removal with an anaerobic baffled reactor

The stringent growth requirements of anammox bacteria may be a challenge for employing the anammox process for nutrient removal at household or decentralized scales, where low maintenance systems are more successful. Enrichment of anammox bacteria was achieved by 100 d using a lab-scale (32 L) anaerobic baffled reactor (ABR). Even though strict anaerobic conditions were not imposed, NH4-N and NO2-N removals of >90% were maintained after ∼100 d, with greatest removals observed in the first two chambers of the four-chamber ABR. Batch anammox activity tests and results of qPCR analyses confirmed the presence of anammox bacteria in all four ABR chambers. Changes in fluorescent peaks and indices supported that intracellular compounds from reactor biomass evolved along the ABR. The presence of denitrifiers, confirmed by qPCR, and lower NO2/NH4 ratios than predicted by stoichiometry indicated that nitrification-denitrification processes also may have contributed to the high N removal in the anammox ABR.