Papers by Keyword: Sulfate-Reducing Bacteria (SRB)

Abstract: The aim of this research is to investigate addition of iron (ferric chloride) to control of sulphate reduction in order to enhance the methane production under laboratory scale. The bioreactor Upflow Anaerobic Sludge Blanket (UASB) undergoes continuous operation under anaerobic condition treating synthetic sulphate enriched wastewater. The wastewater used as influent wastewater with a total COD 8000 mg.L^-1. The experiment was conducted for about 64 days and was operated at constant OLR of 2.0(±0.1) kgCOD.m^-3.d^-1 by maintaining a hydraulic retention time (HRT) of 4 days. The UASB then were feed with sulphate and give the COD/SO₄ ratio 5.3, 2.5 and 1.5. Then amount of ferric chloride at 10.4, 22.2 and 44.5 mM was introduce just after methane producing bacteria (MPB) were completely inhibited by sulphate reducing bacteria (SRB) due to decreasing of methane composition (CH₄) and high level production of hydrogen sulphide (H₂S). The obtained results showed that the FeCl₃ negatively impacted the anaerobic digestion process since with each of COD/SO₄^2- ratio, and the amount addition of ferric chloride to feed regime, gives promotion on methane production, with 67, 70 and 69% after approximately 10 to 15 days operating at critical conditions.

Abstract: Acidic saline lake systems are an uncommon type of natural extreme environment described in Northern Chile and in Australia. These environments are considered a terrestrial analogue to certain ancient Martian terrains and a source of new material for biotechnological applications as bioleaching at high ionic strength conditions and biological systems for precipitating metal sulfides. The aim of this study is to describe the occurrence of redox couples that support prokaryotic life in the system and to obtain representative cultures of predominant microorganisms/metabolisms. Mapping of the area of interest and geochemical analysis of sediments, bedrock and water samples were performed. The original microbial community and enriched cultures were studied by direct count and culturing dependent and independent techniques. In the distal part of the alluvial fans some ponds are found with acidic brines (up to pH 1) of the Cl-SO4-Na (-Mg) type that are surrounded by yellow efflorescences. Other ponds towards the basin center progressively increase in concentration due to capillary evaporation. Brines are rich in aluminium and boron with lower concentration of manganese, lithium, iron and arsenic. An advanced hydrothermal argillic alteration affecting the country rocks, native sulfur associated to active solfataras, alunite and jarosite occurrences in sediments and chloride and sulfate efflorescent salts were evidenced. The microbial community in brines and sediments (10⁵ and 10⁶ cells/mL, respectively) was dominated by Firmicutes, Proteobacteria and Actinobacteria, and by Proteobacteria and Cyanobacteria, respectively. Sulphur and iron oxidation activity were detected depending on the salinity of the samples. Culture enrichments that respire and reduce As (V) and sulfate have been only obtained from sites with the highest pH (4-5). Microbial assemblages in those heterotrophic cultures were closely related to the Gamma and Betaproteobacteria, meanwhile, Rhodanobacter and Shewanella were the only microorganisms detected in the autotrophic cultures supplemented by Na₂S and by H₂. Relevant information to describe the occurring surface biogeochemical processes in that acidic saline system has been obtained. In addition, the occurrence of new prokaryotic genera capable of arsenic redox transformation has been evidenced in acidic systems.

Abstract: Reactors hydrodynamic condition and the choice of substrate are important factors for the optimization and implementation of this sulphate-reducing biological process. This study evaluated two continuous anaerobic reactors, UASB and fluidized bed. The maximum removal achieved by the UASB reactor when operated without recirculation was 65% for a substrate load applied to 3.55 kg/m3 d. When the mass transfer conditions of the reactor were improved by recirculating the biomass, the sulphate removal efficiency increased to 89%, representing a removal rate of 1.94 kg SO₄^2-/m^-3 .d^-1. Glycerol was used with the carbon and electron source for SRB in the fluidized bed reactor and was compared to the performance with lactate. For the same sulphate load applied, a removal efficiency of 70%-90% was observed, resulting in a residual concentration average of 254 mg/L sulphate. Glycerol, which is a by-product from biodiesel production, is a potential choice as substrate for sulphate reduction.

Abstract: Ouro Preto/MG/Brazil soils are rich in arsenic containing minerals that once solubilized may contaminate water or food. Arsenic (As) is toxic if ingested or inhaled. Microorganisms and organic matter plays an important role in the dynamics of As in soils and sediments affecting its mobilization. Aims: to study the mobility of arsenic in the presence of organic matter and sulfur reducing bacteria (SRB) and also to obtain some As resistant bacterial cultures. Materials: Soil samples were collected from abandoned gold mines named Old Mine, Chico Rei and Santa Rita. As content in solid samples were in a range of 465 to 1829 mg Kg^-1. Soil samples (5 g) were mixed with 35 ml of 2.5 M, CaCl₂, stirred (5 min) and allowed to rest at 21.0°C for 1, 30, 60, 90 and 120 days. Other set of experiments were prepared following the previous procedure with some modifications: (i) group 1, flasks with bacterial inoculum (4 ml) from an enrichment of 5 g of soil and 45 ml of liquid medium B Postgate, pH 7.0, incubated at 35°C under anaerobic conditions; (ii) group 2, flasks with (5 g) of organic matter with As (III) adsorptive capacity (powdered chicken feathers - PCF), and (iii) group 3, flasks containing bacterial inoculum and organic matter. Results: As solubility was inversely proportional to time and depends on Fe and Mn contents. The influence of microorganisms on As immobilization was more relevant than the presence of organic matter. Surprisingly, in some cases, As solubility enhanced in the presence of PCF besides its As adsorptive capacity. One microbial consortium adapted to the culturing at pH 5.0 was obtained and this is an interesting feature considering the acid pH of the studied arsenic soils. Indigenous bacteria phenotypically similar to SRB may contribute to As immobilization in natural or impacted environment.

Abstract: A low pH sulfidogenic bioreactor, maintained between pH 2.8 and 4.0, was used to lower sulfate concentrations in two extremely acidic (pH 1.3 to 3.0) synthetic mine waters that contained ferrous iron but no other chalcophilic metals. Tests with water carried out with synthetic mine water from a German site showed that 98% of the sulfate present could be removed by manipulating the water pH and concentration of electron donor (glycerol) for the sulfate-reducing bacteria. While more sulfate was removed with synthetic Chilean mine water (up to 35 mmoles L^-1), this only accounted for between 50-60% of the total present. There was close agreement between the stoichiometry of glycerol used and the amount of sulfate removed, particularly with the German mine water.

Abstract: In this work we have examined the bacterial diversity from the hot spring sediment Agua del Limón (AL1) present at the geothermal Caviahue-Copahue system using a combination of molecular and cultivation techniques, with particular emphasis on indigenous anaerobic prokaryotes. Microorganisms involved in the iron (Acidithiobacillus ferrooxidans and Leptospirillum spp.) and sulphur (Acidithiobacillus spp., Thermotogales-like bacteria, Thiomonas sp., and Desulfurella sp.) cycles were identified in the clone library. Although no obvious sulfate-reducing bacteria were detected by culture-independent techniques, several isolates related to the mesophilic, spore-forming sulfate-reducer "Desulfobacillus acidavidus" strain CL4 were isolated at 30°C and 40°C. The 16S rRNA gene of another isolate showed 94% similarity to Desulfotomaculum thermobenzoicum. Sulfate-reducing enrichment cultures of the Copahue samples were also dominated by "Dsb. acidavidus" CL4.

Abstract: Corrosion control of glutaraldehyde biocide for 304 stainless steel in simulated cooling water system containing sulfate-reducing bacteria (SRB) was studied by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The results revealed that impedance values of stainless steel electrode increased gradually while the passive current densities decreased with the increasing concentration of glutaraldehyde. The biocide improved good anti-corrosion performance to stainless steel in bacteria system. The impedance value |Z|_0.05 increased from 19.72 kΩ·cm² to 33.77 kΩ·cm², and the passive current density reduced from 0.93 μA·cm^-2 to 0.16 μA·cm^-2 when the glutaraldehyde concentration reached 80 mg/L.

Abstract: Bacterial concentration is detected by the cultivation-microscopy method and the serial dilution method in the different oil field sewage. The results indicate that the results are the same when the bacterial concentration in the clear water, simulated water and waterflooded sewage were detected by the cultivation- microscopy method and the serial dilution method. The order of magnitude are the same and quotient are different when the bacterial concentration in the polymer- flooded sewage were detected by those. The bacterial concentration by the cultivation-microscopy method detected is more than by the serial dilution method detected when the waterflooded sewage and the polymer-flooded sewage were joined the biocide. They are used to detect the bacterial concentration in the different concentration scop of polymers, the results are the same in the concentration scop of polyacrylamide under 100mg/L, while the results are very different in the concentration scop of polyacrylamide above 200mg/L.

Abstract: The formation of fouling in stainless steel tube was simulated in the existence of both sulfate-reducing bacteria and iron bacteria under the experimental conditions of the water temperature 30±0.2^°C and velocity of 0.4m/s with the dynamic simulation apparatus of shell-and-tube circulating cooling water. The paper studied the relation between water quality parameters and formation of fouling, such as Fe²⁺ concentration, CODcr and the total number of bacteria. The experimental results showed that: the main reason of the fouling resistance increase was the presence of sulfate-reducing bacteria and iron bacteria. The interaction between iron bacteria and sulfate-reducing bacteria accelerated the formation of biofouling. The influence of each parameter codetermined the formation of microbial fouling.

Abstract: This study, conducted with the dynamic simulation equipment under constant conditions of water temperature 30°C and flow rate 0.4 m.s-1, is intended to simulate dynamically the fouling process on stainless steel tube heat exchanger of three types of fouling microorganisms, iron bacteria (IB), sulfate-reducing bacteria (SRB) and slime forming bacteria (HB), which are isolated from the slime in the bottom of circulating cooling tower. This experiment was tested through the on-line monitoring of fouling resistant and analysis of the characteristics of heat transfer ,the results indicate that induction period for the formation of biofouling in the stainless steel tube by slime-forming bacteria is 56 h, Iron bacteria is 25h, and sulfate-reducing bacteria is 22h. Among these bacteria, the greatest impact on the heat transfer is taken by the iron bacteria, and the sulfate-reducing bacteria are next.