Absence Of Sulfate-reducing Bacteria Research Articles

“Innovative high pressure/high temperature, multi-sensing bioreactors system for microbial risk assessment in underground hydrogen storage”

This study addresses the microbial risks associated with Underground Hydrogen Storage (UHS), a critical component in the transition towards renewable energy systems, by employing an innovative multi-reactor system (Bio-xplorer) to simulate UHS conditions in two Italian reservoirs. The microbiological risk assessment (MRA) of Reservoir A and B was evaluated by subjecting them to gas mixtures of 10 % H2 and 90 % CH4, and 99 % H2 and 1 % CO2, respectively.In Reservoir A, the stability of pressure and temperature, the negligible optical density, and lack of microbial metabolites suggested a low risk of microbial activation. Molecular analyses confirmed the absence of sulphate-reducing bacteria (SRB) and limited growth of hydrogenotrophic methanogens (HM). Similarly, in Reservoir B, the absence of SRB and limited occurrence of HM indicated a low microbiological risk. Overall, the present work supports the safe and efficient implementation of UHS, a promising mitigation technique for climate change, using an innovative tool for MRA.

Role of Sulfate-Reducing Bacteria in the Removal of Hexavalent Chromium by Biosynthetic Iron Sulfides (FeS1+x)

The reduction of Cr(VI) by biosynthesis iron sulfides (FeS1+x) under anoxic conditions has been studied extensively. However, the role of sulfate-reducing bacteria (SRB) when FeS1+x containing SRB removes contaminants during in situ remediation still needs further study. The secondary kinetic constant of biosynthetic FeS1+x with the presence of SRB (called BS-FeS1+x) was 1.72 times that of FeS1+x with the absence of SRB (called BNS-FeS1+x) under FeS1+x:Cr(VI) molar ratio = 10:1, indicating that SRB had a promoting effect on the removal of Cr(VI). Additionally, XPS showed that 5.7% of Cr(VI) remained in the solid phase in the BS-FeS1+x system, indicating BS-FeS1+x could not only remove Cr(VI) by reduction but also by adsorption. Meanwhile, the Cr(VI) removal efficiency of BS-FeS1+x was 100% under anoxic conditions with FeS1+x:Cr(VI) molar ratio = 1:1, which was higher than BNS-SRB (93.4%). SRB could enhance the Cr(VI) removal efficiency, which was possibly due to the constant release of S(-II) and the improvement of the stability and dispersion and the buffering effect. This discovery provided an inspiring idea of the application of biosynthetic iron sulfides to in situ remediation.

Geochemistry of Early Diagenesis of Bog Deposits by the Example of the Holocene Section of the Dulikha Peat Bog (Eastern Baikal Region)

Abstract —Two cores of the Dulikha peat bog deposits, 4.0 and 5.2 m thick, were studied in detail. The reduction type of diagenesis has been established. Decomposition of the organic matter of the bog deposits begins already in the upper intervals of the section at the earliest stages of diagenesis. Microbiological studies of the peat bog revealed numerous organotrophic, ammonifying, nitrifying, and phosphate-mobilizing microorganisms as well as Fe-Ox and Mn-Ox microorganisms and showed the almost complete absence of sulfate-reducing bacteria (except for the lower intervals of the peat section). The processes of the nitrogen, phosphorus, and carbon cycles are more active than the sulfur cycle processes. The chemical composition of the bog water changes during diagenesis. The contents of HCO3-, NH4+, PO43-, NO3- and Corg increase in the peat bog section, which is the result of the destruction of organic matter, leading to the transition of the most mobile and labile components into the bog water. The results of physicochemical modeling show that the high content of organic matter significantly changes the chemical composition of the bog water. The enrichment of the latter in Cu, Zn, Sr, Ba, As, Si, Al, and Pb indicates a diagenetic transformation of the bog deposits. A change of oxidizing conditions by reducing ones in the peat bog leads to the reduction of oxidized Fe (III) and Mn (IV) forms to mobile Fe (II) and Mn (II) forms and their subsequent migration from the solid phase of deposits into the bog water. With depth, the reduced S (II) forms become predominant in the peat, which indicates more reducing environmental conditions. The concentration of SO42- decreases in the pore water of the peat-underlying mineral deposits, which marks the beginning of sulfate reduction. This process, however, is very slow in the bog deposits because of the acid environmental conditions and the lower degree of transformation of organic matter.

Copper corrosion monitoring by electrical resistance probes in anoxic groundwater environment in the presence and absence of sulfate reducing bacteria

In this study the results from corrosion monitoring of copper in anoxic simulated ground water in the presence and absence of sulfate-reducing bacteria (SRB) enriched from the planned disposal site of high level nuclear waste are presented. Copper electric resistance (ER) probes were applied as a physical tool for monitoring corrosion of copper disposal canister. The results are compared to those obtained by linear polarization resistance (LPR) measurements, conducted for parallel OFP-Cu specimens during the experiments, and by weight loss measurements. ER probe method was the most sensitive to corrosion and gave the most conservative estimation of the lifetime of copper. Independently whether the environment was abiotic or biotic, ER probe data showed relatively similar trends to the results from LPR and weight loss measurements. Difference in sensitivity of the methods arises from different ability to detect pitting corrosion and microbial activities on specimen surfaces in the two environments.

Microbial corrosion of X52 pipeline steel under soil with varied thicknesses soaked with a simulated soil solution containing sulfate-reducing bacteria and the associated galvanic coupling effect

In this work, corrosion of an X52 pipeline steel under soil layers with varied thicknesses soaked with a simulated soil solution was investigated in the absence and presence of sulfate-reducing bacteria (SRB) by weight-loss testing, bio-testing, electrochemical measurements and surface analysis techniques. Results demonstrate that, in anaerobic, sterile soil solutions, the presence of a soil layer on the steel surface accelerates the steel corrosion, with the corrosion rate increasing from 0.01 mm/y for uncovered steel to an average of 0.04 mm/y when the soil layer thickness exceeds 5 mm. The presence of SRB in the soil solution increases remarkably the corrosion of bare steel, with an average corrosion rate up to 0.68 mm/y. However, the presence of a layer of soil on the steel surface decreases the steel corrosion. As the soil layer thickness increases, the corrosion rate further decreases, along with the decreased counts of sessile SRB cells on the steel surface. This is attributed to the blocking effect of the soil layer on transport of SRB cells and nutrients towards the steel surface. A galvanic coupling effect exists between bare steel and the soil-covered steel, where SRB contribute to the galvanic corrosion effect. The galvanic current measured in the presence of SRB is considerably higher than that in the absence of SRB.

Corrosion of copper in oxygen-deficient groundwater with and without deep bedrock micro-organisms: Characterisation of microbial communities and surface processes

Copper specimens were exposed to oxygen-deficient artificial groundwater in the presence and absence of micro-organisms enriched from the deep bedrock of the planned nuclear waste repository site at Olkiluoto island on the western coast of Finland. During the exposure periods of 4 and 10 months, the copper specimens were subjected to electrochemical measurements. The biofilm developed on the specimens and the water used in the exposures were subjected to microbiological analyses. Changes in the water chemistry were also determined and surfaces of the copper specimens were characterized with respect to the morphology and composition of the formed corrosion products. The results showed that under biotic conditions, redox of the water and open circuit potential (OCP) of the copper specimens were generally negative and resulted in the build-up of a copper sulphide, Cu2S, layer due to the activity of sulphate-reducing bacteria (SRB) that were included in the system. In the 4-month test, the electrochemical behaviour of the specimens changed during the exposure and alphaproteobactria Rhizobiales were the dominant bacterial group in the biofilm where the highest corrosion rate was observed. In the 10-month test, however, deltaproteobacteria SRB flourished and the initial electrochemical behaviour and the low corrosion rate of the copper were retained until the end of the test period. Under abiotic conditions, the positive water redox potential and specimen OCP correlated with the formation of copper oxide, Cu2O. Furthermore, in the absence of SRB, Cu2O provided slightly inferior protection against corrosion compared to that by Cu2S in the presence of SRB. The obtained results show that the presence of microorganisms may enhance the passivity of copper. In addition, the identification of key microbial species, such as SRB thriving on copper for long time periods, is important for successful prediction of the behaviour of copper.

Microbiologically Induced Corrosion of X80 Pipeline Steel in a Near-Neutral pH Soil Solution

MIC of X80 pipeline steel in a near-neutral pH soil solution in the presence and absence of sulfate-reducing bacteria (SRB) was monitored by electrochemical techniques and microbiological tests. The results show that soil solution is more close to the complex soil environment around pipeline. The activity of SRB leads to the shift of the phase response to low frequency, the decrease of electrolyte resistance and the alteration of dielectric constant of the film. Both the activity and metabolite of SRB influence the corrosion behavior of the steel. The steel surface undergoes localized attack in the SRB-inoculated soil solution, whereas only slight uniform corrosion occurs in the sterile soil solution.

Corrosion of mild steel in sea mud containing sulphate reducing bacteria

In this work, the corrosion behaviour of a mild steel was studied in a sea mud extracted solution in the absence and presence of sulphate reducing bacteria (SRB) by electrochemical impedance spectroscope measurements and scanning electron microscope characterisation. The presence of SRB in the sea mud extracted solution affects corrosion of steel remarkably. In the absence of SRB, the steel corrosion is somewhat inhibited by the formed corrosion product layer. However, the addition of SRB enhances corrosion of the steel due to its metabolism activity. It is speculated that the formed sulphide product may experience transformation decreasing the protectiveness of the product layer.Dans ce travail, on a étudié le comportement à la corrosion d’un acier doux dans une solution extraite de la boue marine, avec ou sans la présence de bactéries sulfatoréductrices (SRB), au moyen de mesures au spectroscope de l’impédance électrochimique et de la caractérisation au microscope électronique à balayage. La présence de SRB dans la solution extraite de la boue marine affecte la corrosion de l’acier de façon remarquable. En absence de SRB, la corrosion de l’acier est quelque peu inhibée par la couche formée par le produit de la corrosion. Cependant, l’addition de SRB augmente la corrosion de l’acier à cause de l’activité de son métabolisme. L’hypothèse est que le produit sulfuré formé peut se transformer, diminuant ainsi l’effet protecteur de la couche produite.

Electrochemical behavior of steel A36 under disbonded coating in the presence of sulfate-reducing bacteria

Variation and distribution of the environmental parameters (potential, current, pH and [Cl−]) and electrochemical behavior of steel A36 were studied in a crevice under a disbonded coating in soil extract solutions in the presence and absence of sulfate-reducing bacteria (SRB). Results show that the crevice blocks the penetration of cathodic currents, and weakens the cathodic polarization of the steel in the crevice. The presence of SRB in the crevice leads to alkalization of the solution and increases energy consumption of the cathodic protection system. The forming of the reversed potential increases the cathodic current. SRB restrains corrosion of the steel in the earlier period due to the protective biofilms, whereas it SRB corrosion of the steel in the later period because of exfoliation of the films and the formation of the corrosive microcell.

Geochemistry and mobilization of arsenic in Shuklaganj area of Kanpur–Unnao district, Uttar Pradesh, India

The level of arsenic (As) contamination and the geochemical composition of groundwater in Shuklaganj area located on the banks of the Ganges Delta of Kanpur-Unnao district were elucidated. Samples (n = 59) were collected from both India Mark II hand pumps (depth, 30-33 m) and domestic hand pump tube wells (10-12 m) located within 5 km from the banks of Ganges. Samples were analyzed for various parameters, including total inorganic As, sulfate, nitrate, alkalinity, ammonia, and iron. Hydrochemistry of the groundwater aquifer was studied through the trilinear plots between monovalent and divalent cations and anions. In Indian mark II hand pumps, arsenic concentration ranged from below detection limit to 448 μg/L. Most of the samples contained both As(III) and As(V). The pH of the samples ranged from 7.1 to 8.2. Except for a few, most of the samples were reducing in nature as evident by their negative oxidation reduction potentials. A positive correlation for arsenic with iron, ammonia, and dissolved organic carbon shows the probability of biodegradation of organic matter and reductive dissolution of Fe oxyhydroxide processes to leach As in aquifers. For confirmation of the suggested arsenic mobilization mechanism, the presence and absence of sulfate-reducing bacteria and iron-reducing bacteria were also tested.

Effect of COD/SO 42−ratio and Fe(II) under the variable hydraulic retention time (HRT) on fermentative hydrogen production

The effect of chemical oxygen demand/sulfate (COD/SO 4 2−) ratio on fermentative hydrogen production using enriched mixed microflora has been studied. The chemostat system maintained with a substrate (glucose) concentration of 15 g COD L −1 exhibited stable H 2 production at inlet sulfate concentrations of 0–20 g L −1 during 282 days. The tested COD/SO 4 2− ratios ranged from 150 to 0.75 (with control) at pH 5.5 with hydraulic retention time (HRT) of 24, 12 and 6 h. The hydrogen production at HRT 6 h and pH 5.5 was not influenced by decreasing the COD/SO 4 2− ratio from 150 to 15 (with control) followed by noticeable increase at COD/SO 4 2− ratios of 5 and 3, but it was slightly decreased when the COD/SO 4 2− ratio further decreased to 1.5 and 0.75. These results indicate that high sulfate concentrations (up to 20,000 mg L −1) would not interfere with hydrogen production under the investigated experimental conditions. Maximum hydrogen production was 2.95, 4.60 and 9.40 L day −1 with hydrogen yields of 2.0, 1.8 and 1.6 mol H 2 mol −1 glucose at HRTs of 24, 12 and 6 h, respectively. The volatile fatty acid (VFA) fraction produced during the reaction was in the order of butyrate > acetate > ethanol > propionate in all experiments. Fluorescence In Situ Hybridization (FISH) analysis indicated the presence of Clostridium spp., Clostridium butyricum, Clostridium perfringens and Ruminococcus flavefaciens as hydrogen producing bacteria (HPB) and absence of sulfate reducing bacteria (SRB) in our study.

Biocorrosion of AISI 304 Stainless Steel by Desulfovibrio desulfuricans in Seawater

The corrosion behavior of AISI 304 stainless steel (SS304) in a batch system of enriched artificial seawater (EASW) in the presence of a sulfate-reducing bacteria (SRB) species (Desulfovibrio desulfuricans ATCC 27774) was investigated using analytical techniques including electrochemical impedance spectroscopy (EIS), atomic force microscopy (AFM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). EIS analysis showed that the polarization resistance of SS304 decreased after immersion in EASW in the presence of the SRB for 14 days compared to the control sample (in the absence of SRB). The corrosion processes were simulated using equivalent circuit models, which provided electrochemical information on the liquid/surface interface for both abiotic and biotic systems. Using AFM, pits and cracks were observed on the stainless steel surface in the presence of SRB, and a thick biofilm produced by SRB was evident in SEM micrographs, which corroborated the EIS results for the explanat...

SRB-biofilm influence in active corrosion sites formed at the steel-electrolyte interface when exposed to artificial seawater conditions

Electrochemical evolution of the interface formed by carbon steel exposed to artificial seawater with nutrients in the presence and absence of mixed cultures that contain sulfate-reducing bacteria (SRB) is characterized by electrochemical impedance spectroscopy (EIS). The artificial seawater in sterile conditions progressively covered the surface of the steel sample with two different layers after 30 days of exposure. An outer layer is formed by a mixture of chlorides and phosphorus-based iron corrosion products with organic compounds from the culture media, and an inner layer is formed by corrosion products mixture constituted mainly by phosphorus-base products. Alternatively, under biotic conditions there was one heterogeneous layer composed by a mixture of phosphorous and sulfur-based corrosion products and biofilm. Three time constants were observed with EIS for sterile conditions. At low frequencies one constant is associated with the charge transfer resistance related to the iron dissolution reaction and inversely proportional to the active area; the porous resistance magnitudes at medium frequencies characterized the physicochemical properties of the inner layer, and high frequency described the electrical properties of the outer mixture layer. Low carbon steel in the presence of SRB (halophilic hydrogenotrophic) showed the impedance distribution after the formation of a corrosion product thick black layer mixed with organic composites and bio-entities. The SRB-biofilm enhanced the corrosion rate and influenced the appearance of diffusion controlled mechanism process. Electrical passive analogs in terms of constant phase elements characterized the evolution of the cover films formed and the impedance of the layers with time. The mechanisms are characterized based on the impedance response for three time constants in the absence of SRB and one time constant with a finite Warburg element when SRB are present in the electrolyte. The validation of the theoretical approximation with electrical analogs was in good agreement with the experimental results.

Electrochemical analysis of the microbiologically influenced corrosion of steels by sulfate-reducing bacteria

The differences between the general corrosion and microbiologically influenced corrosion (MIC) of steels were investigated in terms of its electrochemical behavior and surface phenomena. The corrosion potential of steels in the absence of SRB (sulfate-reducing bacteria) shifted to a negative value with the immersion time. However, the potential of the presence of SRB shifted to a positive value after 30 days' incubation, indicating the growth of SRB biofilms on the test metal specimens and the formation of corrosion products. In addition, the color of a medium inoculated with SRB changed from gray to black. The change in color appeared to be caused by the formation of pyrites (FeS) as a corrosion product, while no significant change in color was observed in a medium without SRB inoculation. Moreover, corrosion rates of various steels tested for MIC were higher compared to those of steels in the absence of SRB. In particular, the corrosion current density of TMCP steels in the presence of SRB was larger than that of other steels. Pitting corrosion was also observed at the surface of all steels in the SRB-inoculated medium. The pitting corrosion likely occurred due to SRB that was associated with the increasing corrosion rates through increasing cathodic reactions, which caused a reduction of sulfate to sulfide as well as the formation of an oxygen concentration cell.

Microbiologically Induced Corrosion of 70Cu-30Ni Alloy in Anaerobic Seawater

The corrosion of 70Cu-30Ni alloy induced by sulfate-reducing bacteria (SRB) in seawater was investigated by microscopic and electrochemical methods. Under anaerobic conditions, the SRB attached on the alloy surface formed blotchy biofilms, as observed by confocal laser scanning microscopy. Intergranular corrosion of the alloy occurred after immersion in SRB-containing seawater for 7 days, as observed by atomic force and scanning electron microscopy. Compared to the control experiment in the absence of SRB, a 330 mV shift of open-circuit potential resulted in the active direction and the polarization resistance decreased by a factor of 10. Electrochemical impedance spectroscopy data revealed that the impedance had remarkable capacitive characteristics. The response of the impedance was determined by two time constants for both the media with and without SRB. Analyses of concentrations of bacteria, metabolites, Cu, and Ni showed that the variation of concentrations of metabolites coincided with the growth of bacteria, and copper and nickel precipitated due to the production of metal sulfide. The effect of bacteria growth was the precipitation of cuprous sulfide to lower the potential of the anodic reaction and the reduction of hydrogen sulfide as the possible cathodic reaction. © 2004 The Electrochemical Society. All rights reserved.

Anaerobic electrochemical corrosion of mild steel in the presence of extracellular polymeric substances produced by a culture enriched in sulfate-reducing bacteria.

The corrosion of mild steel in a seawater medium containing extracellular polymeric substances (EPS) produced by sulfate-reducing bacteria (SRB) was studied by electrochemical experiments and atomic force microscopy (AFM). Under anaerobic conditions, the corrosion of mild steel increased up to 5-fold in the presence of a 1% (w/w) EPS solution but in the absence of SRB. The enhanced corrosion is mainly due to the oxidizing power of EPS with a reduction potential of E1/2 at -0.54 V (saturated calomel electrode), which is 0.4 V above that of hydrogen reduction. The electrochemical reduction of EPS provides a couple to iron oxidation, as demonstrated by H-shaped cell experiments in which the steel sample and EPS are not in physical contact but are ionically connected via the solution and electronically connected through an external wire. Fourier transformation infrared spectroscopy and X-ray photoelectron spectroscopy showed that EPS derived from SRB are comprised of 60% proteins, 37% polysaccharides, and 3% hydrocarbons. The XPS results showed that, upon corrosion, polysaccharide components were mostly converted to hydrocarbons.

Hexadecane decay by methanogenesis.

The potential for the biological conversion of long-chain saturated hydrocarbons to methane under anaerobic conditions has been demonstrated by using an enrichment culture of bacteria to degrade pure-phase hexadecane1. The formation of methane in hydrocarbon-rich subsurface zones could be explained if a similar conversion of long-chain alkanes to methane were to take place in subsurface environments. If this process could be stimulated in the subsurface, it could be used to enhance hydrocarbon recovery from petroleum reserves1,2. Parkes2, however, questions the environmental significance of the enrichment-culture results1 on the grounds that alkane conversion to methane is very slow and because sulphate-reducing and methanogenic bacteria might both be necessary for even this slow process to occur, restricting the conversion to specialized, unusual zones in sediments. Here we show that, on the contrary, subsurface bacteria can adapt to convert hexadecane to methane rapidly and in the absence of sulphate-reducing bacteria.

Biocorrosion of mild steel by SRB: electrochemical studies

Electrochemical studies of the biocorrosion of mild steel in the presence and absence of sulfate reducing bacteria (SRB) grown in lactate/sulfate and lactate/nitrate aqueous media were performed. Open circuit potential measurements revealed a displacement of the potential in the noble direction in both media. However, regular oscillations in the potential were observed only in the lactate/sulfate medium. SEM micrographs showned pits clearly distributed over the surface of the steel samples exposed to SRB cultures in both media, with small size and more uniform pits in the lactate/sulfate media, in agreement with the open circuit potential data. Cyclic voltammetry clearly shows that the SRBs grown in the lactate/sulfate medium lead to high dissolution rates in the transpassive region with the formation of Fe(III) species.

The effect of sulphate-reducing bacteria on the electrochemical behaviour of corrosion-resistant alloys in sea water

Corrosion potential ( E corr ), polarisation resistance ( R p ) and potentiodynamic polarisation measurements were conducted on UNS NO4400 (Monel 400) and UNS NO8904(904L) stainless steel in de-aerated sea water in the presence and absence of sulphate-reducing bacteria (SRB). These measurements as well as morphological studies were conducted after different exposure intervals of up to 26 d to the test environment. In the absence of SRB both alloys were readily passivated. The anodic polarisation behaviour of both alloys was remarkably affected by the presence of SRB. Thus exposure of alloy 400 to an SRB environment for 5 hr led to the appearance of an active dissolution peak and prolonged exposure led to a diminishing of the passive region. The anodic polarisation curves pertaining to 904L alloy showed a change in behaviour after 14 d where an active/passive transition was recorded and pitting attack below scattered bacterial colonies was detected. However, under open circuit conditions no pitting was observed. E corr for both alloys shifted in the active direction and R p decreased with the increase of exposure time to SRB. EDX analysis indicated sulphide-rich layers on alloy 400 which were responsible for the loss of passivity.