• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2002.09a
• /
• pp.122-124
• /
• 2002

The removal capacity of zero-valent iron for Cr(Ⅵ) was evaluated using batch kinetic tests. The rate constants for zero-valent iron dramatically increased as initial Cr(Ⅵ) concentration decreased. Generally, the reaction rates of Cr(Ⅵ) with zero-valent iron were faster than that of a biotic degradation of Cr(Ⅵ), and furthermore the reaction rates were inversely proportional to the initial Cr(Ⅵ) concentrations. After certain reaction time elapsed. no further decrease of Cr(Ⅵ) was observed, indicating a loss of iron reactivity. The loss of iron reactivity was primarily due to the passivation of iron surfaces with iron-Cr precipitates, but the reactivity of iron was recovered by adding iron-reducing bacteria. Even though the addition of bacteria itself removed Cr(Ⅵ), the combination of iron-reducing bactera and oxidized iron significantly enhanced the reaction rate for Cr(Ⅵ) removal. The results from column tests also confirmed that the innoculation of iron-reducing bacteria to the column containing completely oxidized iron partially enhanced the recovery of the iron reactivity.

• Journal of Microbiology and Biotechnology
• /
• v.24 no.2
• /
• pp.280-286
• /
• 2014

Four thermophilic bacterial species, including the iron-reducing bacterium Geobacillus sp. G2 and the sulfate-reducing bacterium Desulfotomaculum sp. SRB-M, were employed to integrate a bacterial consortium. A second consortium was integrated with the same bacteria, except for Geobacillus sp. G2. Carbon steel coupons were subjected to batch cultures of both consortia. The corrosion induced by the complete consortium was 10 times higher than that induced by the second consortium, and the ferrous ion concentration was consistently higher in iron-reducing consortia. Scanning electronic microscopy analysis of the carbon steel surface showed mineral films colonized by bacteria. The complete consortium caused profuse fracturing of the mineral film, whereas the non-iron-reducing consortium did not generate fractures. These data show that the iron-reducing activity of Geobacillus sp. G2 promotes fracturing of mineral films, thereby increasing steel corrosion.

• Journal of Conservation Science
• /
• v.26 no.4
• /
• pp.407-416
• /
• 2010

Bacteria with ability for iron reduction in the soil can use corrosion products of iron remains as energy source. The activities of this bacteria cause the change of corrosion products. As a result, it can be difficult to identify corrosion products promoting corrosion of iron remains. The purpose of this study, is to investigate the change in corrosion products that bacteria causes and to improve understanding about the corrosion of iron remains. To simulate corroded condition of excavated iron remains, carbon steel corroded by solution of NaCl and $Na_2SO_4$ was prepared. Then the prepared carbon steel was immersed in a liquid medium with bacteria. The incubation period was 42days. After experiment, the carbon steel was analyzed by SEM-EDS, X-ray diffraction method. The result is that the carbon was changed to green because of activity of bacteria and that the plate crystal and lozenge crystal were generated on the corrosion specimen. Also, we confirmed that the activities of bacteria differenciated colors and forms of corrosion products.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.2
• /
• pp.123-129
• /
• 2005

In situ permeable reactive barrier (PRB) technologies have been proposed to reductively remove organic contaminants from the subsurface environment. The major reactive material, zero valent iron ($Fe^0$), is oxidized to ferrous iron or ferric iron in the barriers, resulting in the decreased reactivity. Iron-reducing bacteria can reduce ferric iron to ferrous iron and iron reduced by these bacteria can be applied to dechlorinate chlorinated organic contaminants. Iron reduction by iron reducing bacteria, Shewanella algae BrY, was observed both in aqueous and solid phase and the enhancement of TCE removal by reduced iron was examined in this study. S. algae BrY preferentially reduced Fe(III) in ferric citrate medium and secondly used Fe(III) on the surface of iron oxides as an electron acceptor. Reduced iron formed reactive materials such as green rust ferrihydrite, and biochemical precipitation. These reactive materials formed by the bacteria can enhance TCE removal rate and removal capacity of the reactive barrier in the field.

• KSBB Journal
• /
• v.15 no.2
• /
• pp.201-207
• /
• 2000

The traditional ripening method of clay was analyzed. An advanced refining method of clay using enrichment cultures of iron r reducing bacteria was developed. After the traditional ripening, the whiteness of the clay was increased due to removal of | iron impurities by inhabitant dissilmaltien with iron reducing bacteria. Other characteristics of the refined clay such as v viscosity, plasticity, and strength were also improved by iron reducing bacteria. An advanced method of clay refinement with a anaerobic enrichment cultivation of iron reducing bacteria supplemented with an extra carbon source such as glucose was s suggested. When the clay was treated by the advanced method. the refinement time could be reduced to 1/6 of that r required by the traditional method. The physical properties of the refined clay by the advanced method were better than t those of the traditionally refined clay.

• Journal of Korean Society of Environmental Engineers
• /
• v.29 no.7
• /
• pp.833-838
• /
• 2007

In this study, adhesion and transport of bacteria in positively-charged media was investigated with batch and column experiments. Bacterial species used in this study was Escherichia coli ATCC 11105(length: 2.2 ${\mu}m$, diameter: 0.6 ${\mu}m$) and media used were quartz sand(particle size distribution: 0.5-2.0 mm, mean diameter: 1.0 mm) and iron-coated sand. Batch results indicate that bacterial adhesion increased as the content of iron-coated media increased. At iron-coated media 0%(quartz sand 100%), around 46% of bacteria was adhered to media while at iron-coated media 100%(quartz sand 0%) about 97% was attached. Column results also show that bacterial adhesion was enhanced with an increase of iron-coated media content. As the iron-coated media content increased from 0 to 100%, bacterial adhesion increased from 8 to 94%. The experimental results demonstrate that positively-charged media could influence transport of bacteria in porous media.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.8
• /
• pp.798-807
• /
• 2008

Due to economic impairment derived from metal corrosion of pumping station installed around coastal area, it was needed for related cause-effect to be investigated for understanding practical corrosion behavior and providing proper control. This research was thus carried out to determine whether the microbe can influence on metal corrosion along with its control in the laboratory. For this study, groundwater was sampled from the underground pump station(i.e. I Gas Station) where corrosion was observed. Microbial diversity on the samples were then obtained by 16S rDNA methods. From this, microbial populations showing corrosion behaviors against metals were reported as Leptothrix sp.(Iron oxidizing) and Desulfovibrio sp.(Sulfur reducing) Iron oxidizing bacteria were dominantly participating in the corrosion of iron, while sulfate reducing bacteria were more preferably producing precipitate of iron. In case of galvanized steel and stainless steel, iron oxidizing bacteria not only enhanced the corrosion, but also generated its scale of precipitate. Sulfate reducing bacteria had zinc steel corroded greater extent than that of iron oxidizing bacteria. In the inactivation test, chlorine or UV exposure could efficiently control bacterial growth. However as the inactivation intensity being increased beyond a threshold level, corrosion rate was unlikely escalated due to augmented chemical effect. It is decided that microbial corrosion could be differently taken place depending upon type of microbes or materials, although they were highly correlated. It could be efficiently retarded by given disinfection practices.

• KSBB Journal
• /
• v.15 no.2
• /
• pp.208-213
• /
• 2000

Using three types of porcelain clays such as White, Blue, and Yellow clays, which were used as raw materials for Bae씨a, C Chungja, and common porcelains, the biological refinement by an enrichment culture of iron reducing bacteria was studied. | In the biological clay refining, amounts of leached iron increased as increasing sucrose $\infty$ncentration, which was s supplemented as a carbon and electron donor source for cell growth and iron reduction. Total amounts of the leached iron a and specific rate of iron reduction were dependent on the types of the clay. Strength and chromaticity of refined clays which a are important properties required for porcelain clays were improved as increasing sucrose concentration. The degree of s shrinking, however, did not changed. the redness among the chromaticity of refined clays is favorably reduced through the r ripening by the iron reducing bacteria. Considering iron removal efficiency and the change of physical properties, the optimal c concentration of sucrose was 4%(w/w) in the clay.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2002.04a
• /
• pp.250-253
• /
• 2002

Remediation of groundwater using zero valent iron filings has received considerable attention in recent years. However, zero valent iron is gradually transformed to iron(III) oxides at permeable reactive barriers, so the reduction of iron(III) oxides can enhance the longevity of the reactive barriers. In this study, microbial reduction of Fe(III) was performed in anaerobic condition. A medium contained nutrients similar to soil solution. The medium was autoclaved and deoxygenated by purging with 99.99% $N_2$ and pH was buffered to 6, while the temperature was regulated as 2$0^{\circ}C$. Activity of iron reducing bacteria were not affected by chlorinated organics but affected by iron(III) oxide. Although perchloroethylene(PCE) was not degraded with only ferric oxide, PCE was reduced to around 50% with ferric oxide and microorganism. It shows that reduced iron can dechlorinate PCE.

• 한국방재학회:학술대회논문집
• /
• 2008.02a
• /
• pp.807-810
• /
• 2008

Permeable reactive barriers containing Zero-valent iron (ZVI) are used to purify ground-water contaminants. One of the representative contaminant is trichloroethylene (TCE). ZVI can act as a reducing agent of TCE. When ZVI is oxidized to Ferric iron, TCE reduced to Ethene, which is non-harmful matter. As a ZVI becomes ferric iron, the reducing effect decreases and iron becomes unavailable. So, constant reduction of TCE requires the regular supply of reducing agent. So, we use Iron-reducing bacteria(IRB) to extend the TCE degrading ability. We perform three experiment DI water, DI water with medium, and DI water with medium and IRB. By the experiment we try to found the dissolve ability.