Evaluation of the denitrifying microbiota of anoxic reactors

Removal of inorganic nitrogen compounds from wastewaters can be accomplished by a combination of the biological processes of nitrification and denitrification. The information on the microbiota present in denitrifying reactors is still scarce. In the present work the evaluation of the denitrifying microbiota of different reactor sludges was performed by specific activity measurements and MPN count of denitrifiers. We also present the isolation and physiological and phylogenetic characterisation of denitrifying bacteria from the anoxic reactor of a combined system treating landfill leachate. Specific denitrifying activity measurements were faster to perform and more reliable than MPN enumerations. 16S rDNA characterisation of the isolates showed that they belonged to the genera Thauera, Acidovorax and Alcaligenes and were closely related to microorganisms retrieved from ecosystems rich in recalcitrant compounds. Two of the isolates could grow on aromatic compounds as sole carbon source.