Use Of Sulfate-reducing Bacteria Research Articles

Synergistic passivation performance of cadmium pollution by biochar combined with sulfate reducing bacteria

The use of sulfate-reducing bacteria (SRB) for the remediation of Cd-contaminated soil is an attractive option. However, there are various factors that limit the activity of free SRB in soil, which hinders the rapid reduction of sulfate. The immobilized SRB technology has been proposed as a possible solution to overcome this barrier. This study aimed to isolate an Enterobacter sp. strain (SRB15-3-2) with high resistance to Cd2+ from a tailing. Wheat, maize, and rice straws were selected to prepare biochar for inoculating the screened bacteria. The results showed that wheat straw biochar pyrolyzed at 700 °C (WS700) had the highest performance in carrying SRB for Cd2+ immobilization. Furthermore, the WS700 was found to promote SRB15-3-2 for offering S2− and functional groups (C-S, C=O, C=C, C-C=O, and C-O-C, etc.) during the immobilization process. The immobilized SRB with WS700 (ISRBWS700) agglomerated and reacted with Cd2+ to form metal precipitations, predominantly CdS and CdCO3. Which lead to a significant decrease of exchangeable-Cd in contaminated soil (with initial Cd concentrations of 1, 5, and 20 mg/kg) by 18.5%–31.6% after applying the ISRBWS700, indicating that the indigenous soil microbes were been protected from Cd toxicity. Additionally, ISRBWS700 exhibited a synergistic effect in enhancing SRB15-3-2 propagation and the activities of saccharase, urease, and acid phosphatase, compared to the separate treatment of SRB15-3-2 and WS700. Overall, ISRBWS700 prepared in this study represented an accessible way to resolve Cd-contaminated soil, which provided new theoretical insights into eco-friendly technologies for Cd-polluted soil remediation both in development and sustainable aspects.

Use of sulfate-reducing bacteria and different organic fertilizer for bioremediation of ex-nickel mining soils

The microbiological activity associated with exmining soil remediation can be considered useful to accelerate the contaminant degradation. The use of sulfate-reducing bacteria (SRB) and organic matter exhibits potential in improving ex-nickel mining soil quality. The purpose of this study was to examine the ability of SRB in several organic fertilizers to reduce sulfate and nickel ions, and to increase pH of soil from nickel in mining areas. This study used the bacteria collection of the Soil Laboratory of the Faculty of Agriculture, Universitas Muslim Indonesia. Those were previously isolated from two cultivating pond of milkfish in the Kuri area of Maros Regency, South Sulawesi, Indonesia. The soil samples were collected from ex-mining areas of the Vale Indonesia Enterprise in Soroako, South Sulawesi, Indonesia. Those were mixed with organic fertilizers, generated from sugarcane sludge, manure, and Quickstick (Gliricidia sepium) leaves, each with 50 and 100 g doses. The 5 kg soil samples were put into a pot and mixed evenly with organic fertil- izers. A general linear model (GLM) repeated measures analysis of variance (ANOVA) was adopted to analyze the data. The results of this study indicate that the application of SRB and fertilizer was effective in reducing concentration of sulfate and nickel. Among the three types of organic fertilizers, manure was effective in reducing sulfate and nickel concentrations, while Quickstick fertilizer was the more effective in stabilizing pH level. Fertilizer doses exhibited a significant effect on decreasing sulfate and nickel concentrations, but it exhibited no significant effect on stabilizing pH levels. At 10 days after treatment (DAT), the sulfate concentration decreased from 2,530 ppm to 1,443 ppm in treatment of SRB and manure with dose of 50 g and 1,363 ppm with that of 100 g. At the end of the observation (30 DAT), those were decreased to 1,217 ppm in treatment of SRB and manure with doses of 50 g and 1,167 ppm with that of 100 g. Among the three types of organic fertilizers used, Quickstick demonstrates the more effective reduction rate. At 10 DAT, pH increased in SRB treatment by 7.06 at a concentration of 50 g and 7.01 at a concentration of 50 g. At the end of the observation (30 DAT), the pH became 6.67 at a concentration of 50 g and 6.82 at a concentration of 50 g. The nickel concentration decreased from an origin concentration to 1,950 ppm in treatment of SRB and manure with doses of 50 g and 1,690 ppm with that of 100 g. Thus, the application of manure fertilizer and the addition of SRB is recommended for bioremediation of sulfate and nickel from ex-mining soil.

Selectively enriched mixed sulfate-reducing bacteria for acrylamide biodegradation

Acrylamide (AM) is a carcinogen and neurotoxicant, and its growing application in numerous industrial processes is contaminating the environment. In addition, the inhibitory effect of AM makes its biodegradation in the environment challenging. This study investigated AM degradation using a selectively enriched inoculum of mixed sulfate-reducing bacteria (SRB) isolated from a local wastewater treatment plant in Daegu, Korea. The use of SRB is promising for effectively treating several environmental pollutants, but the feasibility for biodegrading AM has not yet been reported. Experimental results showed that 73% AM (initial concentration: 7 mM) biodegradation was achieved in just 120 h, together with 42% and 96% TOC and sulfate removal, respectively. In addition, the SRB performance was not significantly affected by a threefold increase in the AM concentration; biodegradation performance dropped by only 12%. These results imply SRB immunity toward lethal contaminants and the viability of using SRB in different treatment processes. The kinetic results of batch studies enabled development of a pseudo-first-order kinetic model for AM biodegradation, TOC, and sulfate removal. In addition, although the sulfate removal efficiency was affected by a higher sulfate loading, it had little effect on AM and TOC removal. This study shows the potential of using SRB to effectively degrade recalcitrant pharmaceutical pollutants.

An efficient, cost-effective method for determining the growth rate of sulfate-reducing bacteria using spectrophotometry

The use of sulfate reducing bacteria (SRBs) in laboratory studies is a common approach for investigating microbially influenced corrosion (MIC). The characteristic formation of black iron sulfide precipitates during SRB growth, however, preclude the use of traditional spectrophotometric approaches for capturing growth data instead necessitating labour-intensive or technically specialized approaches. As such, an understanding of SRB growth responses to experimental conditions is often missing from MIC studies. Bernardez and de Andrade Lima (2015) have outlined a spectrophotometric approach for estimating SRB cell mass via the addition of HCl. This method has potential for the study SRB growth however its applicability is currently limited by the use of large aliquot volumes (45 mL), which restrict the number of timepoints that can sampled from one culture, and the extensive time devoted to cell preparation prior to OD readings.•We demonstrate an improved method for capturing SRB growth data via spectrophotometry following acidification. We incorporate lower sample volumes and adapt the method described in Bernardez and de Andrade Lima (2015) to a high throughput microtiter plate approach that increases the efficiency of this method and its applicability to growth rate studies.•Our results allay theoretical concerns that acidification may distort growth rate analysis by impacting cells differently depending on their metabolic state.•We further demonstrate that this method (acid-amended OD measurements) is more accurate and far more cost efficient than traditional methods (dilution spread-plate counting) and popular molecular methods (quantitative PCR) currently in use in SRB growth research.

Separation and recovery of Pd and Fe as nanosized metal sulphides by combining solvent extraction with biological strategies based on the use of sulphate-reducing bacteria

Platinum group metals (PGMs) are highly demanding metals in current high-techs. However, their supply is limited due to their scarcity in natural resources and expensive mining. Solvent extraction in combination with microbial communities were employed for the recovery of palladium from aqueous media. Accordingly, extraction of Pd(II) by N,N′-dimethyl-N,N′-dicyclohexylthiodiglycolamide (DMDCHTDGA) in toluene and subsequent stripping by acidic thiourea were carried out, followed by bio-recovery employing biogenic sulphide generated from sulphate-reducing bacteria. The results revealed an excellent extraction performance of DMDCHTDGA towards Pd(II) from metal complex mixtures in 2, 4 and 6 M HCl. However, Fe(III) was co-extracted from 4 and 6 M HCl, being completely removed with deionized water during scrubbing. 94–99% of extracted Pd(II) were stripped using acidic thiourea. Over 99% of stripped Pd(II) were recovered using two solutions containing biogenic sulphide: an effluent from a bioremediation process of acid mine drainage treatment, and a supernatant solution from Postgate B nutrient medium. 78–99% of scrubbed Fe(III) were bio-recovered. Analysis of all the precipitates collected during palladium bio-recovery showed that they were composed by Pd and S, which is consistent with the synthesis of nanosized PdS. The elemental analysis of the iron precipitate also suggests the presence of iron sulphide. Henceforth, the method engaged is environmentally sustainable, safe and cheap, thus attractive to be employed, to separate and recover both Pd and Fe from waste materials.

Comparison of the efficiency of chitinous and ligneous substrates in metal and sulfate removal from mining-influenced water

Mining-influenced water (MIW) remediation is challenging, not only due to its acidity and high metal content, but also due to its presence in remotely located mine sites with difficult surrounding environments. An alternative to common remediation technologies, is the use of sulfate-reducing bacteria (SRB) to achieve simultaneous sulfate reduction and metal removal in on-site anaerobic passive systems. In these systems, the organic carbon source (substrate) selection is critical to obtaining the desired effluent water quality and a reasonable treated volume. In this study, we evaluated the use of two different substrates: a chitinous product obtained from crushed crab shells, and a more traditional ligneous substrate. We put the substrates, both with and without water pretreatment consisting of aeration and pH adjustment, in anaerobic experimental columns. The treatment with the chitinous substrate was more effective in removing metals (Al, Cu, Fe, Cd, Mn, Zn) and sulfate for a longer period (458 days) than the ligneous substrate (78 days) before suffering Zn breakthrough. The reactors fed with pretreated water had longer operational periods and lower metals and sulfate concentrations in the effluent than those with untreated influent water. Zn was consistently removed to levels <0.3 mg/L for 513 days in the chitinous substrate columns, while levels <0.3 mg/L were maintained for only 140 days in the ligneous substrate pretreated column. The highest sulfate removal rates achieved in this study were in the range of 5–6 mol/m3/d for the chitinous substrate and 1–2 mol/m3/d for the ligneous substrate. Overall, the chitinous substrate proved to be more efficient in the removal of all the aforementioned metals and for sulfate when compared to the ligneous substrate. This could be the determinant when selecting a substrate for passive systems treating acidic MIW, particularly when Zn and Mn removal is necessary.

Removing arsenic and hydrogen sulfide production using arsenic-tolerant sulfate-reducing bacteria

Environmental remediation technologies that involve the use of sulfate-reducing bacteria constitute a feasible alternative to the remediation of sites polluted with heavy metals and metalloids. The present study evaluates hydrogen sulfide production and arsenic removal by two microbial consortia (C1 and C2) in batch systems exposed to different arsenic concentrations and oxidation states. We identify the following three consecutive stages of arsenate removal: (1) hydrogen sulfide production/accumulation, (2) arsenate reduction to arsenite associated with the incomplete oxidation of hydrogen sulfide to elemental sulfur and (3) arsenic polysulfide precipitation as the main arsenic removal mechanism from aqueous solution. Kinetic parameters are determined in regard to the arsenic oxidation state through the fit of hydrogen sulfide production. The r max reached by C1 and C2 is increased seven- or eightfold when 250 mM As[+5] was used instead 250 mM As[+3]. Arsenic removal by extracellular precipitation of arsenic polysulfides associated with elemental sulfur precipitation detected through scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM–EDS) can explain the exceptional value of r max observed at 250 mM during As[+5] exposition.

Metagenomic Analysis Indicates Epsilonproteobacteria as a Potential Cause of Microbial Corrosion in Pipelines Injected with Bisulfite

Sodium bisulfite (SBS) is used as an oxygen scavenger to decrease corrosion in pipelines transporting brackish subsurface water used in the production of bitumen by steam-assisted gravity drainage. Sequencing 16S rRNA gene amplicons has indicated that SBS addition increased the fraction of the sulfate-reducing bacteria (SRB) Desulfomicrobium, as well as of Desulfocapsa, which can also grow by disproportionating sulfite into sulfide, sulfur, and sulfate. SRB use cathodic H2, formed by reduction of aqueous protons at the iron surface, or use low potential electrons from iron and aqueous protons directly for sulfate reduction. In order to reveal the effects of SBS treatment in more detail, metagenomic analysis was performed with pipe-associated solids (PAS) scraped from a pipe section upstream (PAS-616P) and downstream (PAS-821TP) of the SBS injection point. A major SBS-induced change in microbial community composition and in affiliated hynL genes for the large subunit of [NiFe] hydrogenase was the appearance of sulfur-metabolizing Epsilonproteobacteria of the genera Sulfuricurvum and Sulfurovum. These are chemolithotrophs, which oxidize sulfide or sulfur with O2 or reduce sulfur with H2. Because O2 was absent, this class likely catalyzed reduction of sulfur (S0) originating from the metabolism of bisulfite with cathodic H2 (or low potential electrons and aqueous protons) originating from the corrosion of steel (Fe0). Overall this accelerates reaction of of S0 and Fe0 to form FeS, making this class a potentially powerful contributor to microbial corrosion. The PAS-821TP metagenome also had increased fractions of Deltaproteobacteria including the SRB Desulfomicrobium and Desulfocapsa. Altogether, SBS increased the fraction of hydrogen-utilizing Delta- and Epsilonproteobacteria in brackish-water-transporting pipelines, potentially stimulating anaerobic pipeline corrosion if dosed in excess of the intended oxygen scavenger function.

Nickel, manganese and copper removal by a mixed consortium of sulfate reducing bacteria at a high COD/sulfate ratio

The use of sulfate-reducing bacteria (SRB) in passive treatments of acidic effluents containing heavy metals has become an attractive alternative biotechnology. Treatment efficiency may be linked with the effluent conditions (pH and metal concentration) and also to the amount and nature of the organic substrate. Variations on organic substrate and sulfate ratios clearly interfere with the biological removal of this ion by mixed cultures of SRB. This study aimed to cultivate a mixed culture of SRB using different lactate concentrations at pH 7.0 in the presence of Ni, Mn and Cu. The highest sulfate removal efficiency obtained was 98 %, at a COD/sulfate ratio of 2.0. The organic acid analyses indicated an acetate accumulation as a consequence of lactate degradation. Different concentrations of metals were added to the system at neutral pH conditions. Cell proliferation and sulfate consumption in the presence of nickel (4, 20 and 50 mg l(-1)), manganese (1.5, 10 and 25 mg l(-1)) and copper (1.5, 10 and 25 mg l(-1)) were measured. The presence of metals interfered in the sulfate biological removal however the concentration of sulfide produced was high enough to remove over 90 % of the metals in the environment. The molecular characterization of the bacterial consortium based on dsrB gene sequencing indicated the presence of Desulfovibrio desulfuricans, Desulfomonas pigra and Desulfobulbus sp. The results here presented indicate that this SRB culture may be employed for mine effluent bioremediation due to its potential for removing sulfate and metals, simultaneously.

SULFATE -REDUCING BACTERIA RESISTANT TO INCREASED LEVELS OF HEXAVALENT CHROMIUM

The aim of this work was to study the morpho-physiological and biochemical properties of chromium-resistant sulfate-reducing bacteria and to investigate the nature of electron donors and their acceptors. Methods. Bacteria were cultivated in Postgate B and Postgate C media at temperature 30 °C in 25 ml tubes under the anaerobic conditions. Biomass was determined turbidimetrically using the photoelectrocolorimeter CPK-3 The concentration of Cr (VI) was determined spectrophotometrically by the diphenylcarbazide method. Chromazurol S was used for Cr (III) determination. The sulphates content was determined turbidimetrically after their precipitation by barium chloride. Results. Bacterial cells are oval or rod-shaped. Derived sulfate-reducing bacteria hold incomplete oxidation of organic compounds with acetate formation and do not form spores, gramnegative, mesophillous obligate anaerobes. The optimum temperature for growth is 27–35 °C, pH=7. As a final electron acceptor sulfate-reducing bacteria use sulfate. Bacteria use elemental sulfur, fumarate, Cr (VI), Fe (III), nitrate as a terminal electron acceptor under absence of sulfate in the environment. In presence of sulfate in culture medium all cultures as a source of carbon, used lactate, fumarate, pyruvate, succinate, malate, fructose, glucose, citrate. Acetate, ethanol, butanol, propionate, glycerol did not provide their growth. The effect of different concentrations of chromate on the growth of sulfate-reducing bacteria have been investigated. There were shown the patterns of use of chromate by bacteria, and reduction highly toxic Cr (VI) to less toxic Cr (III). Conclusions. Isolated bacteria, were identified as Desulfomicrobium sp. These sulfate-reducing bacteria, in our opinion, can be used for treatment of water environment from sulfates, nitrates and salts of heavy metals and especially hexavalent chromium.

Bio-Removal of Black Crust from Marble Surface: Comparison with Traditional Methodologies and Application on a Sculpture from the Florence's English Cemetery

In the present study we investigate the use of sulphate-reducing bacteria during the black crust's bio-removal process. The aim of our work is to compare microbial cleaning with more traditional cleaning methods (chemical and laser cleaning) and to discuss the pros and cons of this new technique. The research builds in two steps: a first experimental phase examining the process on stone materials coming from the Cathedral of Florence, on a Carrara marble column taken from the Baccio d’Agnolo Balcony under the Dome by Brunelleschi (treated in our laboratory) and on an external pilaster (treated in situ) on the left side of the Cathedral made out three different stone typologies: green serpentine, red marlstone and white Carrara marble; a second application phase on a marble sculpture from 19th century representing the Allegory of Death from Florence's English Cemetery. The effects of the different procedures on the original surfaces were evaluated by a scanning electron microscopy coupled with energy dispersive X-ray (SEM/EDS) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and colour measurements. Results prove that microbial cleaning is the most controllable process and it has a great efficiency in sulphate removal. These techniques have also a great ecological importance as bacteria reproduce the same biological process achieved in natural contests.

Optimization of cyanidation tailings bioremediation adding nutrients and microorganisms

The objective of this project was to find optimum parameters for the development of bioremediation process of cyanidation tailings by addition of nutrients and microorganisms. It was tested the use of sulfate-reducing bacteria (SRB) to stabilize metal ions through the formation of sulphides and; bacteria able to biodegrade cyanide (BC). Factorial experiments were conducted at level of columns. SRB from Cyanidation tailings were isolated and BC proceeded from pregnant solution of cyanidation. BSR and BC were adapted to tailings. A column test was performed to try: 1. the effect of using 1 and 10 mM lactate to increase the activity of BSR and 2. Addition of 0,1 and 1 mM sodium acetate and phosphoric acid to improve the activity of BC. In order to optimize parameters, it was tested in columns, effect of a mixed culture (SRB-BC) and nutrients (1 mM lactate and Acetate 1mM). Nutrients were found to increase the reduction of sulfate to 48% (average) and the addition of inoculums to 42%. Bioremediation of cyanide was 12%. It was not shown effect on the addition of nutrients or inoculums on Cyanide degradation. Two additional tailings were tested and the addition of 1 mM sodium lactate allowed the induction of BSR in 8 days in one of them.

Growth of various strains of sulfate-reducing bacteria of human large intestine

New strains of sulfate-reducing bacteria from human intestine are obtained. These bacteria are vibrio-like (strains SRB Vib-1, SRB Vib-2, SRB Vib-3) and short rod-like (strains SRB Rod-4 and SRB Rod-5) forms. The growth of these strains of bacteria, usage of sulfates by bacteria and their production of hydrogen sulfide are investigated. The strains of sulfate-reducing bacteria SRB Vib-1, SRB Vib-2, SRB Vib-3 more intensively accumulate biomass, compared with strains SRB Rod-4 і SRB Rod-5. The strains SRB Vib-1 and SRB Vib-2 grow the most intensively. Accumulation of bacterial biomass (3.8 g/l) is the highest on the third day of cultivation, after that the stationary growth phase began. The strain of bacteria SRB Vib-3 accumulates biomass 2.89 g/l on the third day of bacteria cultivation. Maximal biomass of SRB Rod-4 and SRB Rod-5 bacteria strains ranged from 2.59 to 3.25 g/l on the eighth day of cultivation. The obtained sulfate-reducing bacteria intensively use sulfate ions and produce hydrogen sulfide. The strains SRB Vib-1, SRB Vib-2, SRB Vib-3 produce from 2.99 mM to 3.12 mM of hydrogen sulfide. The rod-shaped strains of sulfate-reducing bacteria use sulfate ions and produce hydrogen sulfide less intensely in the presence of sulfates in the medium. Keywords: sulfate-reducing bacteria, Desulfovibrio , Desulfomicrobium , sulfates, hydrogen sulfide, bowel diseases, ulcerative colitis, intestinal microbiocenosis.

Bioremediation of Heavy Metal–Contaminated Soils by Sulfate‐Reducing Bacteria

Many sewage irrigation areas in China have lost their agricultural productivity because they are polluted by cadmium (Cd). Use of sulfate-reducing bacteria (SRB) may have a positive ecological effect on the bioremediation of heavy-metal Cd-contaminated soils. A five-step Tessier sequential extraction procedure to analyze the geochemical speciation of metal Cd and investigate the bioremediation efficiency by SRB was adopted. The results indicate that the SRB can reduce the concentrations of the exchangeable fraction of Cd, which can be easily absorbed by plants. The removal is approximately 70%, which demonstrates bioremediation efficiency. In the contaminated soils before bioremediation, the exchangeable fraction of Cd is the dominate carrier and the fraction of Fe-Mn oxides is next in importance, accounting for 45-60% and 35-55% of the total Cd, respectively. After adding the SRB into the water-logged soils, the concentration of different geochemical speciation of Cd was determined every 7 days for 33 days. During this period, the total concentrations of Cd did not change, while the form of Cd changed significantly. The concentrations of the exchangeable fraction of Cd decreased significantly, which shows that the Cd bioavailability in the soils markedly decreased. The concentrations of the Fe-Mn oxides fraction of Cd rose conspicuously, ranging from 60% to 120%; the concentrations of the carbonate fraction of Cd and organic matter fraction of Cd both increased slightly. The residue fraction of Cd did not change. The scope of oxidation-reduction potential was from 150 mv to -450 mv, and the rate of reduction of sulfate decreased with the increase of total Cd concentration.

Polysulfide reduction using sulfate-reducing bacteria in a photocatalytic hydrogen generation system

A hydrogen generation process using photocatalytic reactions has been proposed. In this process, hydrogen sulfide is a source of hydrogen and is turned into polysulfide. In order to establish the cyclic operation of a photocatalytic hydrogen generation system, it is necessary to convert polysulfide back into hydrogen sulfide with a small energy input. This paper proposes the use of sulfate-reducing bacteria (SRB) for the regeneration of hydrogen sulfide. Batch cultivation of natural source SRB samples were carried out using a culture medium containing polysulfide as the only sulfur compound source. SRB produced hydrogen sulfide from several kinds of polysulfide sources, including a photocatalytic hydrogen generation-produces solution. Production lag phase and production rate of hydrogen sulfide were affected by initial polysulfide concentration. SRB activity was inhibited at high initial polysulfide concentrations. SRB enrichment culture T2, exhibited the highest hydrogen sulfide production rate, and was able to utilize several kinds of organic matter as the electron donor. The results suggest the possibility of using large biomass sources, such as sewage sludge and the raw garbage in a hydrogen generation system. We developed speculative estimates that an SRB based hydrogen generation system is feasible.

Control of metal toxicity, effluent COD and regeneration of gel beads by immobilized sulfate-reducing bacteria

Over the last few decades, the use of sulfate-reducing bacteria (SRB) in the treatment of heavy-metal containing wastewaters including acid mine drainage has become a topic of scientific and commercial interest. However, technical difficulties such as the sensitivity of SRB to toxic metals and high effluent COD limit the widespread use of SRB in high heavy-metal containing wastewater. The aim of this study was to clarify the reasons why the immobilized SRB sludge with inner cohesive carbon source (ISIS) process can endure high metal toxicity and decrease effluent COD. The ISIS process can physically set apart SRB and free the system of external influences such as the surrounding toxic metallic ions, as well as form inner carbon sources to avoid high effluent COD. Metal toxicity and bead durability are the two major factors which influence the regeneration and reuse of gel beads. Reuse of suspended SRB sludge and beads crosslinked with boric acid were unsuccessful due to metal toxicity and agglomeration of beads, respectively. However, beads crosslinked with ammonium sulfate prevented agglomeration of beads allowing successful bead regeneration and reuse. The result of four cyclic trials showed that over 99% of zinc was removed in each trial using these beads.

Treatment of Acid Mine Drainage by Sulphate-reducing Bacteria Using Low Cost Matrices

This paper reports a laboratory-scale investigation concerning the use of sulphate-reducing bacteria (SRB) in a semi-continuous process, where column packed-bed type bioreactors were used for the treatment of acid mine drainage (AMD). The use of different materials as solid matrices was tested and the performance of the bioremediation processes was discussed in terms of sulphate and metals removal and acid neutralization. The behaviour of a reactor filled with acidic soil from a mining area and organic wastes was compared with other three reactors where coarse sand, glass spheres and cereal straw were used as packaging materials. Batch experiments showed the presence and growth of SRB from the acidic soil in different pH conditions and the effect of the absence or presence of several added carbon sources: lactate, ethanol and lactose. The data showed that it is possible to grow SRB using the acidic soil as source of inocula, in the absence and in the presence of the carbon sources tested, since the pH of the media was previously increased to values of 5 or higher. When acidic soil from the mining area and organic wastes were utilised as column matrices, it is possible to remove the metals and to neutralise the acidity of AMD, although an inefficient sulphate removal was observed. When coarse sand or glass spheres were utilised, efficient metals sulphate removal were achieved. However, the incapacity of both systems to generate enough alkalinity does not allow maintaining their good performances in terms of iron removal and sulphate reduction. As a result, the incorporation of materials with neutralizing and buffer capacity to the matrix is recommended. Due to its low density, cereal straw was not suitable to obtain an anaerobic environment inside the column for SRB activity.

A sulfate-reducing bacterium with unusual growing capacity in moderately acidic conditions

The use of sulfate-reducing bacteria (SRB) is a cost-effective route to treat sulfate- contaminated waters and precipitate metals. The isolation and characterization of a SRB strain from an AMD in a Brazilian tropical region site was carried out. With a moderately acidic pH (5.5), the C.1 strain began its growth and with continued growth, modified the pH accordingly. The strain under these conditions reduced sulfate at the same rate as an experiment performed using an initial pH of 7.0. The dsrB gene-based molecular approach was used for the characterization of this strain and its phylogenetic affiliation was similar to genus Desulfovibrio sp. The results show an SRB isolate with unexpected sulfate reducing capacity in moderately acidic conditions, bringing new possibilities for the treatment of AMD, as acid water would be neutralized to a mildly acidic condition.

The use of sulphate-reducing bacteria in bioremediation of ex-coal mining soil

The most serious impact after exploiting coal by opened peat mining is acid mine drainage phenomenon. This is an oxidation of sulphide minerals by releasing sulphate that generate the environment acidity. This study was aimed to observe the ability of sulphate reducing bacteria (SRB) isolated of sludge paper mills in decreasing the ex-coal mining sulphate content. Before inoculating onto the soil, SRB was incubated in the sterilized organic matter for 4 days. Organic matter inhabited SRB mix with ex-coal mining soil (1:3 v/v). As a control was a series ex-coal mining mixed with non inoculated organic matter (1:3 v/v). The experiment is carried out in randomized complete design in 3 replications, each consist of 5 buckets. All buckets were maintained in saturated water content. Every 5 days for 20 days the sulphate content, pH and Eh were assessed to observe the bioremediation progress. The result shown that SRB was able to reduce 84.25% excoal mining sulphate content in 20 days. In consequence, the soil pH was increased from 4.15 to 6.66 during the process. It is recommended that SRB is prospective to be further developed as a sulphate bioremediation agents on ex-coal mining soil.© 2007 Jurusan Biologi FMIPA UNS SurakartaKey words: bioremediation, ex-coal mining, sulphate reducing bacteria

Specific growth rate of sulfate reducing bacteria in the presence of manganese and cadmium

The development of technologies based on the use of sulfate-reducing bacteria (SRB) to treat sulfate contaminated wastewaters has produced a cost-effective route to precipitate metals. In this work the effects of cadmium and manganese in the SRB growth rates were assessed. It was observed that duplication time is 50 h in the presence of cadmium and 6 h in the presence of manganese, thus showing that the SRB growth rate was more affected by the presence of cadmium. A low sulfate reduction (maximum 25%) occurred which was sufficient for metal precipitation. The results are discussed considering their implications for metal precipitation in acid mining drainage.