| The integrated approach of using metal chelate (e.g. Fe(Ⅱ)EDTA) absorption combined with microbial reduction for nitric oxide (NO) removal has been a frequent topic of much recent study. In principle, two types of anaerobic bacterial incubations, including heterotrophic denitrifying bacteria and dissimilatory iron reducing bacteria, are designed to conduct biological reduction of Fe(Ⅱ)EDTA-NO and Fe(Ⅲ)EDTA. Most denitrifying bacteria have been confirmed to have the capabilities to carry out Fe(III)EDTA. Although illuminating, the existing studies failed to provide in-depth insight into these especial microorganisms. Therefore, Paracoccus devitrification ZGL land Paracoccus versutus LYM were used to further investigate the regeneration of scrubber solution for NOx removal, with the aim at exploring the biological conversion of nitrogen and iron. The following aspects were conducted in this paper:1) reduction of Fe(Ⅲ)EDTA in a NOx scrubber liquor by a denitrifying bacterium and the effects of inorganic sulfur compounds on this process;2) Fe(Ⅱ)EDTA-NO reduction coupled with Fe(Ⅱ)EDTA oxidation by a nitrate-and Fe(Ⅲ)-reducing bacterium;3) evaluation of simultaneous reduction of Fe(Ⅱ)EDTA-NO and Fe(Ⅲ)EDTA by a bacterial pure culture. The main findings are as follows:1) The denitrifying bacterium ZGL1could reduce Fe(Ⅲ)EDTA efficiently with glucose as the electron donor. Enzymes analysis indicated Fe(Ⅲ)EDTA reductase of ZGL1were primarily located both in the membrane and cytoplasmic fractions. Better reduction performance was obtained with higher initial cell concentration, which was linearly related with the Fe(Ⅲ)EDTA reduction rate. 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.2) Strain LYM experienced a single anaerobic FeEDTA redox cycling thorough NO-dependent Fe(Ⅱ)EDTA oxidation and dissimilatory Fe(Ⅲ)EDTA reduction in FeEDTA culture. Without glucose addition, Fe(Ⅱ)EDTA-NO reduction rate was at a rather slow rate even in presence of sufficient Fe(Ⅱ)EDTA. Unlike aqueous Fe2+and solid-phase Fe(II), Fe(Ⅱ)EDTA could prevent cells from encrustations. These findings suggested that the occurrence of NDFO preferred the mixotrophic physiology in the presence of an organic cosubstrate.3) Paracoccus denitrification ZGL1conducted simultaneous NO and Fe(Ⅲ)EDTA reduction. Fe(Ⅲ)EDTA reduction was severely inhibited by Fe(Ⅱ)EDTA-NO. Fe(Ⅲ)EDTA was considered to have a positive effect on the reduction of Fe(II)EDTA-NO. Riboflavin. AQDS and vitamin B12at0.1mM did not have significant effects on simultaneous reduction of Fe(II)EDTA-NO and Fe(III)EDTA. Addition of sulfide not only could directly react with Fe(II)EDTA-NO and Fe(Ⅲ)EDTA but also might play multiple roles on biological Fe(II)EDTA-NO reduction and Fe(Ⅲ)EDTA reduction. The respiratory inhibitor CuCl2inhibited both Fe(Ⅱ)EDTA-NO and Fe(Ⅲ)EDTA reduction while NaN3and rotenone showed no measurable effects. |
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