Authigenic mineralization and detrital clay binding by freshwater biofilms: The Brahmani river,India

This study sought to understand the origin and fate of one of the bitumen mounds found on the bottom of Lake Baikal. These mounds are located at a depth of 900 m beneath oil spots detected on the surface of Lake Baikal (53° 18′24^″, 108° 23′20^″). The two mounds were sampled with a manipulator from a “MIR” deep-water manned submersible. Mature mound No. 8 was subjected to chemical and microbiological studies. Mound No. 3 was subjected only to chemical studies; we failed to perform microbiological analyses of this mound for logistic reasons. Oil spots collected from the water surface, samples of mound No. 3 and No. 8, were subjected to GC/MS analysis. The water contained aliphatic hydrocarbons with chains between C₈ and C₂₃, with the most abundant chain length being C₁₈. Mound No. 3 with the most abundant chain length being C₁₈ actively released oil droplets into the water. It contained 770 mg/g of C₁₃-C₃₂ n-alkanes, with a maximum at C₂₃ (160 mg/g). Mound No. 8 was inactive and contained 148 mg/g of aliphatic C₂₂-C₃₄ n-alkanes, with a maximum at C₂₅. Mound No. 8 also consisted of 3% inorganic matter, 48% unresolved complex mixture (UCM) and less than 1% other compounds (polyaromatic hydrocarbons, isoprenoids, carotenoids, and hopanes). The core of this sample used as inoculate, yielded Rhodococci when cultivated on oil as the only source of carbon. Cultivation of the sample on agar-containing Raymond inorganic medium with crude West Siberian oil as the only source of carbon revealed colonies of these bacteria, which all appeared identical. PCR was performed with DNA isolated from 5 colonies, using primers for 16S rRNA genes. Comparison of the sequences of the 5 PCR products over a length of 714 bp revealed that they were almost identical. Phylogenetic analysis of these homologous sequences showed that they were similar to the corresponding sequences of the genus Rhodococcus. Substrate demands, the morphology of the colonies, and SEM and TEM data confirmed that the isolates obtained could indeed be Rhodococci. All of the isolates could grow in bulk cultures with inorganic medium supplemented with crude oil. Moreover, all of the isolates degraded aliphatic hydrocarbons with lengths between C₁₁ and C₂₉. C₂₃-C₂₉ hydrocarbons were degraded completely. The isolates could grow at 4–37°C. The most unexpected finding was that of the many microorganisms capable of consuming oil, only Rhodococci exhibited this ability in the inactive bitumen mound. The possible mechanisms of how crude oil is transformed into bitumen mounds and mature bitumen are discussed.     

Effects of Bitumen Deposit on Soil Physico-Chemical Characteristics

Soils in the bitumen deposit area of Nigeria were analyzed for the physico-chemical characteristics and element contents to determine the level of contamination by the natural resource and to provide a framework for establishing relationships between the chemistry of mineral deposit and its host soils. The physico-chemical parameters were determined using standard analytical methods, while the elemental concentrations were determined by Energy Dispersive X-ray Fluorescence Spectrometry technique. The results revealed that soils had higher concentrations of associated hydrocarbon formation elements than other Nigerian soils but lower than the sand and bitumen fractions of Nigerian bituminous sands, indicating contamination of the bitumen host soils by the mineral deposit. Strong positive correlations existed between some elements in the soils, suggesting common sources or chemical similarities. Positive correlations are shown by the results of the cross plot analysis, which establish relationships between the soils and the bitumen deposit, indicating that contamination of the soils could easily affect other components of the ecosystem, viz water and vegetation.     

Optimization of Lithotrophic Activities of Acidithiobacillus ferrooxidans toward Significant Reduction of Sulfur and Ash from Low Rank Bitumen

In the present study, the potential application of Acidithiobacillus ferrooxidans for elimination of ash and sulfur from bitumen was investigated in batch experiments. A comparison between the bioleaching and abiotic treatments indicated that A. ferrooxidans cells enhanced ash and pyritic sulfur removal by 20 and 59%, respectively. The X-ray diffraction profiles of the samples indicated the precipitation of some mineral elements inside of bitumen decreased the bioleaching performance after 9 days from beginning of the experiments. The effects of bitumen particle size (X₁), agitation speed (X₂) and initial pH (X₃) as interfacial factors each at three levels on the ash removal (Y₁) and pyritic sulfur removal (Y₂) were investigated by response surface methodology as a statistical design of the experiment. On the basis of quadratic models applied to the performance of the bioleaching process, 66.42% of the pyritic sulfur and 50.88% of the ash could be removed after 9 days under optimal conditions, namely a bitumen particle size of 100 µm, an agitation speed of 80 rpm, and initial pH of 2.     

A novel perspective to bitumen refineries life cycle assessment and processes emissions

This study provides an introduction and a novel view of the impacts of oil refineries industry on human health, ecosystem quality and resources. The scope and issues for dealing with these challenges are rather wide and complex because the Oil refineries are complex facilities. Several processes, such as distillation, vacuum distillation, or steam reforming are required to produce a large variety of oil products such as gasoline, light fuel oil or bitumen. The goals, perspectives and expectation for the environmental practice and control have changed dramatically over the last couple of decades. Hence the required approach has to be multidisciplinary, based on established scientific concepts and sound engineering principles. The environmental impacts of oil refineries are assessed using the technique of life cycle assessment (LCA). In this paper, only the material production phase of the bitumen LCA is considered. To improve the quality of the LCA, a regionalized life cycle inventory (LCI) database for the Oil refineries and commercial LCI databases are used to validate and model unit processes with an LCA software.     

Rhizosphere microflora of plants used for the phytoremediation of bitumen-contaminated soil

The microbial communities and their degradative potential in rhizospheres of alfalfa (Medicago sativa) and reed (Phragmites australis) and in unplanted soil in response to bitumen contamination of soil were studied in pot experiments. According to the results of fluorescence microscopy, over a period of 27 months, bitumen contamination of soil reduced the total number of microorganisms more significantly (by 75%) in unplanted than in rhizosphere soil (by 42% and 7% for reed and alfalfa, respectively) and had various effects on some important physiological groups of microorganisms such as actinomycetes as well as nitrogen-fixing, nitrifying, denitrifying, ammonifying, phosphate-solubilizing, sulphur-oxidizing, cellulolytic and hydrocarbon-degrading microorganisms. The changes in the physiological structure of the microbial community under bitumen contamination were found to hinge on not merely the presence of plants but also their type. It was noted that the rhizosphere microflora of alfalfa was less inhibited by hydrocarbon pollution and had a higher degradative potential than the rhizosphere microflora of reed.