Ecophysiological characterization of microbial communities in BioDeNOx

Nitric oxide (NO) and nitrogen dioxide (NO2) are both important Green house gases, which also cause air pollution. Industrial flue gas emissions are responsible for 17% of NOx/SOx released into the atmosphere. Treatment of flue gas to remove NO and NO2 had started a few decades ago and several chemical and biological processes have been developed to remove NOx from the flue gas BioDeNOx is a biological NOx removal process in which microbial communities are used for the reduction of NO to N2 at elevated temperatures (50 to 55 °C). Many microbiologists and process engineers have tried to use pure or co-cultures of bacteria for this purpose, however so far mixed cultures have not been studied extensively. Recently, the BioDeNOx-process has been proposed and developed for the removal of NO from flue gas by Buisman et al. (1999). In this process the NOx is absorbed in a Fe(II)EDTA2- solution followed by microbial denitrification of the NO in Nitrosyl complex (Fe(II)EDTA.NO2-) to N2. This thesis deals with the microbiology of the BioDeNox process. The diversity, identity and activity of the microorganisms performing the above-mentioned reactions are described. This was achieved by the isolation and characterization of the microorganisms, and by using culture-independent molecular tools for the identification and quantification of unculturable microorganisms. In addition, the relationship between diversity and activity in the BioDeNOx process was studied by operating a labscale reactor in which simultaneous Fe(II)EDTA.NO2- reduction and Fe(III)EDTA- reduction were taking place.