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

The potential for using denitrifying bacteria to remove nitrogen oxide s from combustion gas streams was investigated. Nitrous oxide was chos en as a model compound and a number of different bacteria were screene d for their ability to reduce it to nitrogen. Two strains, Pseudomonas denitrificans ATCC 13867 and Paracoccus denitrificans ATCC 17741, exh ibited significantly higher reduction rates than did other bacteria. M aximum reduction occurred at 6 g l-1 glucose and 35-degrees-C with Pse udomonas denitrificans, and at 6 g l-1 glucose and 30-degrees-C with P aracoccus denitrificans. The rate of reduction by Pseudomonas denitrif icans varied with concentration and was a maximum of approximately 0.0 17 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 m m 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 bioproc ess to remove nitrous oxide from combustion gas using either species. However, the ability of these organisms to remove nitrogen oxides in l arger-scale systems needs to be assessed.