THE USE OF DENITRIFYING BACTERIA FOR THE REMOVAL OF NITROGEN-OXIDES FROM COMBUSTION GASES

The potential for using denitrifying bacteria to remove nitrogen oxides from combustion gas streams was investigated. Nitrous oxide was chosen as a model compound and a number of different bacteria were screened for their ability to reduce it to nitrogen. Two strains, Pseudomonas denitrificans ATCC 13867 and Paracoccus denitrificans ATCC 17741, exhibited significantly higher reduction rates than did other bacteria. Maximum reduction occurred at 6 g l-1 glucose and 35-degrees-C with Pseudomonas denitrificans, and at 6 g l-1 glucose and 30-degrees-C with Paracoccus denitrificans. The rate of reduction by Pseudomonas denitrificans varied with concentration and was a maximum of approximately 0.017 mM h-1 (mg dry biomass)-1 at an initial N2O concentration of 0.9 mm. Paracoccus denitrificans attained a maximum removal rate of 0.01 5 mm h-1 (mg dry biomass)-1 at an initial N2O concentration of 1.6 mM. It was concluded that it may be possible to develop a commercial bioprocess to remove nitrous oxide from combustion gas using either species. However, the ability of these organisms to remove nitrogen oxides in larger-scale systems needs to be assessed.