The Depassivation And Dye Decolorization Of Sponge Iron By Bioaugmentation With An Iron Cycling Microbial Consortium

Sponge iron, which is made from iron ore through high heat sintering, is a kind of cheap and porous water treatment materials. It has been widely used in water treatment field due to its large specific surface area, strong enrichment of electrochemical performance and high physical adsorption and flocculation characteristics. However, sponge iron is easier to be passivated dueing the operation process, resulting in system block and treatment efficiency decrease. In this study, the depassivation and dye decolorization of sponge iron were performed by bioaugmentation with an iron-cycling microbial consortium enriched by our lab through constructing the microbial consortium-sponge iron combined reaction system and analyzing the the apparent effects, microscopic changes and the underlying mechanisms. The main results in this thesis were summarized as follows:1. The passivation of sponge iron:The sponge iron was passivation when the concentrations of Fe2+ were decreased 50%, the dye decolorization rates were only 10%, of the highest rate after 12 h performanceand in the reaction system with the sterilized sponge iron acid washed and activated. At this time, the surfaces of sponge iron were covered by oxidized film(such as Fe2O3, Fe(OH)3, Fe3O4) analyzed by scanning electron microscope and X-ray diffraction.2. The depassivation of iron-cycling microbial consortium: The additions of iron-cycling microbial consortium efficiently increased the the concentration of Fe2+ and inhibited the oxidized film formation in the sponge iron dye decolorization systems. Although significantly positive correlations(r=0.956, p<0.01) were between the biomass and the concentrations of Fe2+ and significantly negative correlations were between the pH and the concentration of Fe2+(r=-0.927, p<0.01) in the microbial consortium-sponge iron combined reaction system, closer relationship were observed between the biomass and the concentration of Fe2+(Fe2+/pH r = 0.498, p= 0.026; Fe2+/cell volume r =0.732, p<0.01), suggesting that microbial consortium play important role in the depassivation of sponge iron. When glucose was provided as the carbon sources, the microbial consortium IB reached the highest biomass and the highest Fe2+ concentration(0.67Fe2+/(L. h)) as well. With the increase of the initial pH, the depassivation efficiencies were increase. When the initial pH was 5, the highest of Fe2 + concentration, 1.32 mg Fe2+/(L. h) were obteined in this system. The microbial consortium IB could perform depassivation under aerobic, anaerobic or facultative condition.. Additionally, no significantly change was observed in the community structures of microbial consortium IB before and after the reaction in the different systems by DGGE analysis.3. The enhancement of sponge iron dye decolorization by the microbial consortium IB: Although the microbial consortium IB did not have the capacity for decolorization, the dye decolorization efficiencies of sponge iron could be increased when the consortim presented. The highest decolorizing rates, 98.1%, 98.7% and 98.9%, were obtained under the anaerobic condition with glucose as the carbon sources and pH 5.In conclusion, the microbial consortium IBcould inhibit the formation of oxidized film, accelerate Fe2+ dissolution, and mentain the decolorizing ability of sponge iron under aerobic, anaerobic and facultative conditions. These results will provide important scientific basis for the wastewater treatment usring sponge iron technologies..