Reduction of Fe(III)EDTA in a NOx scrubber liquor by a denitrifying bacterium and the effects of inorganic sulfur compounds on this process

Biological reduction of Fe(III)EDTA is one of the key steps in nitrogen oxides removal in the integrated approach of metal chelate absorption combined with microbial reduction. Paracoccus denitrificans ZGL1 was used as a model bacterium to evaluate the process of Fe(III)EDTA reduction by such microorganisms that could carry out the simultaneous reduction of NO chelated by Fe(II)EDTA (Fe(II)EDTA-NO) and Fe(III)EDTA. Enzymes analysis indicated Fe(III)EDTA reductase of ZGL1 was located both in the membrane and cytoplasmic fractions. Glucose was identified as the most efficient electron donor for Fe(III)EDTA reduction. Better reduction performance was obtained with higher initial cell concentration corresponding to a specific reduction rate of 8.7 μmol h−1 mg protein−1. The presence of sulfate and thiosulfate had no influences on both cell growth and Fe(III)EDTA reduction. Fe(III)EDTA reduction rate and cell growth could be inhibited by addition of sulfite mainly due to its direct and indirect toxic effects.

► The denitrifying bacterium Paracoccus denitrificans could reduce Fe(III)EDTA.
► Fe(III)EDTA reductase was located in membrane and cytoplasmic fractions.
► Fe(III)EDTA reduction rate was linearly related with initial protein concentration.
► Sulfite inhibited Fe(III)EDTA reduction due to direct and indirect toxic effects.