The Research On Reduction Of Fe(Ⅱ)EDTA-NO Using Paracoccus Denitrificans ZGL1in NO_x Absorption Solution

Nitrogen oxide(NOx), consisting of95%nitric oxide(NO) and5%nitrogen dioxide (NO2), which are emitted from fossil fuel combustion, are one of the major air pollution sources. With a large number of NOx discharge, they can cause various environmental problems, such as acid rain formation, ozone depletion and global warming. Therefore, the NOx removal technology from flue gas has become an important content in the field of air pollution control.Our team put forward biological combined with complex absorption simultaneous desulfurization and denitrification. As a part of this study, Paracoccus denitrificans ZGL1, to be used to study the Fe(Ⅱ)EDTA-NO removal mechanism in heterotrophic conditions, and to explore the Fe(Ⅱ)EDTA-NO removal in different nutrient conditions; and to discuss the inorganic sulfur compounds (SO42-,SO32-and S2O32-) have the effects on Fe(II)EDTA-NO removal.P. denitrificans can use glucose and Fe(Ⅱ)EDTA as electron donors to reduce Fe(Ⅱ)EDTA-NO. Glucose was primary electron donor in the initial stage. In the later stage, the bacterium could easily use Fe(Ⅱ)EDTA as an electron donor due to the increase of Fe(Ⅱ)EDTA and the consumption of glucose. P. denitrificans were also capable of reduction of Fe(Ⅲ)EDTA with glucose as the electron donor, thus regenerating NOx absorption solution. In addition, several substances within the bacterium discharged into the system during cell metabolism and reacted with Fe(Ⅲ)EDTA. This resulted in the increase of Fe(Ⅱ)EDTA concentration. EDTA and SO42-in the system were not related to the change in Fe(Ⅱ)EDTA concentration.Under four different nutrient conditions, i.e., without additional glucose, additional glucose, additional thiosulfate and additional glucose and thiosulfate, found that strain ZGL1could use Fe(Ⅱ)EDTA as electron donor to reduce Fe(Ⅱ)EDTA-NO, but it was impossible to grow without additional glucose. When glucose and thiosulfate were added into the system, the strains could grow well under the glucose co-substrate conditions. It could use glucose and Fe(Ⅱ)EDTA as electron donor to reduce Fe(Ⅱ)EDTA-NO, and the process of sulfur autotrophic denitrifying occurred according to using S2O32-in the system, making the Fe(Ⅱ)EDTA-NO reduction rate increased. But in the absence of external glucose complexing denitrification by adding S2O32-, the strains cannot grow and sulfur autotrophic denitrifying process cannot occur. In the above four different nutrient condition, the reduction product of Fe(II)EDTA-NO the was mainly N2, N2O only appeared briefly as an intermediate product.Inorganic sulfur compounds had a different influence on biological reduction of Fe(II)EDTA-NO. SO42-had no influences on both Fe(II)EDTA-NO reduction and cell growth; SO32-could inhibit cell growth and affect Fe(II)EDTA-NO reduction process, and it also can react with Fe(II)EDTA-NO directly, which can produce N2O, so that the final N2reduced and N2O increased; S2O32-can promote the cell growth and increase Fe(II)EDTA-NO reduction rate in relatively.