Kinetic Characterization of Brocadia spp.-Dominated Anammox Cultures.

Abstract

The microbial anaerobic ammonium oxidation (anammox) process has interesting engineering applications for an efficient and economical removal of nutrient nitrogen from wastewater bearing high ammonium and relatively low organic matter composition. Currently, there is a need to have reliable estimates of kinetic parameters that can improve the understanding and the modeling of the anammox process for optimizing onsite applications. In this work, a multi-substrate kinetic model explaining the activity of the anammox process based on substrates consumption is proposed using well characterized granular (GS) and flocculent (FS) biomass sources mostly composed by Candidatus Brocadia fungida and Candidatus Brocadia caroliniensis, respectively. Kinetic parameters were very similar irrespective of the biomass source (GS: KS of 0.64 (NH4+) and 0.35 (NO2-) mM, and specific Vmax of 0.69 (NH4+), 0.88 (NO2-), 0.64 (N2) and 0.23 (NO3-) mmol g-1 VSS h-1. FS: KS of 0.53 (NH4+) and 0.37 (NO2-) mM, and VSmax of 0.67 (NH4+), 0.86 (NO2-), 0.64 (N2) and 0.25 (NO3-) mmol g-1 VSS h-1). The model respected the experimentally calculated stoichimetry of N-compounds, which serves as an independent validation. Also, growth kinetics of the FS was studied, calculating an YX/S of 0.111 mol C-biomass mol-1 N2 produced and a µmax of 0.0041 h-1, which corresponds to a doubling time of 6.9 d. The model data from FS was used for determining the equation of the anammox reaction. Slight differences with the previously established stoichiometries were found, overall with respect to the yield of NO3- and the biomass (reaching 0.353 mol NO3- and 0.105 mol C mol-1 NH4+ consumed), which were related with the r-metabolic strategy of FS. As a concluding remark, the kinetic understanding of the anammox biomass described in this work can be used for optimizing ulterior applications.