Fe(III)(EDTA) Biological Reduction under Thermophilic Conditions by Anaerobic Sludge

Abstract

A novel process for removal of NO using Fe(II)(EDTA) absorption and microbial reduction has been demonstrated, in which a portion of the Fe(II)(EDTA) was oxidized by oxygen in flue gas to form Fe(III)(EDTA). The biological reduction of Fe(III)(EDTA) was crucial for continuous removal of NO. The biological reduction of Fe(III)(EDTA) by anaerobic sludge under thermophilic conditions (55 ºC) was investigated. The effects of key parameters such as the carbon source, pH and NO₂^–, NO₃^– and SO₃^2- contents on the Fe(III)(EDTA) reduction rate were investigated in batch experiments. The results showed that the Fe(III)(EDTA) reduction rate depended on the carbon source, with the highest reduction rate (60.45 %) being achieved with glucose, followed by sodium acetate, ethanol, methanol and formic acid. The optimal pH was 7.5, which produced an Fe(III)(EDTA) reduction rate of 64 % after 96 h. In addition, the Fe(III)(EDTA) reduction rate was influenced by the NO₂^–, NO₃^– and SO₃^2- contents and its inhibition was in proportion to the initial concentrations. This study demonstrated that Fe(III)(EDTA) could be effectively reduced by microorganisms under thermophilic conditions at 55 ºC.