Hydrocarbon-polluted Sites Research Articles

Microbial Consortium for Polycyclic Aromatic Hydrocarbons Degradation from Petroleum Hydrocarbon Polluted Soils in Rivers State, Nigeria

The study investigated the distribution of polycyclic aromatic hydrocarbon (PAH) degraders across two different petroleum hydrocarbon-polluted sites in the Niger Delta, Nigeria, and the ability of the reconstituted indigenous consortium to utilize these PAHs. Microorganisms were isolated after sample enrichment in naphthalene and anthracene, and biosurfactant production was measured using the emulsification index technique. PAH concentrations of approximately 6000 mg/kg and 9000 mg/kg in Tombia and Bodo were higher than the Department of Petroleum Resources (DPR) intervention limit of 40 mg/kg. The pH, soil texture and high conductivity affected microbial distribution significantly. A total of 12 bacteria from the genera Bacillus, Pseudomonas, Micrococcus and 3 fungal isolates (Fusarium, Aspergillus and Penicillium) from the 2 sites were able to utilize naphthalene and/or anthracene as sole carbon source. While the Tombia site had more microorganisms capable of PAH degradation with the redox indicator 2, 6-dichlorophenol indophenol (DCPIP) (10 bacterial and 3 fungal species), two bacterial species from Bodo were able to produce biosurfactant. The findings of this study indicate that indigenous microbes in the polluted sites are catabolically active and could be further stimulated for an effective eco-friendly and green removal of PAHs from oil-polluted soils while combined.

Benefitting multi-enzyme system for the purpose of improving the flow properties of waxy oil

The research work encompasses the potential of hydrocarbon-degrading recombinant enzymes for improving the flow properties of a Malaysian waxy oil. During transportation in pipeline, waxy oil has a tendency to lose its flowability due to heat loss and deposited in the pipeline, causing major production loss. Chemicals were injected proactively at production platform to counter the problem via modulation of the wax flow properties. However, chemicals are not highly effective. Enzymatic degradation of hydrocarbon was vastly studied for bioremediation of hydrocarbon-polluted sites but its application for wax treatment was limitedly reported. This concept worth a feasibility study as an alternative to chemical treatment. In this study, Malaysian waxy oil was treated with both chemical and recombinant enzymes, and the resulting effect on oil flow properties was discussed. First, treatment of oil with chemical yielded a reduction in pour point by 1–2 °C and viscosity by 11–46%. Next, a newly proposed set of recombinant enzymes identified from a modified alkane metabolism pathways were mixed as a multi-enzyme system and brought to reaction with oil in a shaking incubator at a controlled temperature, reaction time and agitation speed, resulted in reduction of pour point (3–5 °C) and viscosity (19–40%). Nonpolar solvent was added to selected enzyme formulations to overcome the hydrophobicity of the waxy oil. A better decrement in pour point (5–9 °C) and viscosity (25–79%) were achieved when the oil was treated with 1 and 2 wt% enzyme in solvent. A carbon distribution analysis revealed 30–50% long-chain carbon fraction in enzyme-treated oil were broken down into shorter chain carbon fraction. A morphology study discovered that the sharp and dense wax crystals in untreated oil disappeared. On the contrary, the wax crystals shown a dispersed pattern after treated with enzyme, which discouraged the wax from assemble into network and precipitated. As a result, a delayed appearance of wax crystal in treated oil (60–70.1 °C) is observed in contrast to untreated oil (75 °C). Finally, chemical and enzyme treatments were compared by wax deposition behavior in a simulated pipeline assemble. Oil treated with enzyme formulation yielded a lower wax deposition rate (0.09–0.3 g/m2) as compared to chemical (0.1–0.5 g/m2) over the course of 4 hours, suggesting enzyme's role in causing the delay in wax precipitation. The preceding results demonstrate that the flow properties of waxy hydrocarbon can be improved using the proposed set of immobilized recombinant enzymes with a comparable performance to chemical, therefore it is a valuable alternative.

Treatment of Motor Oil-Contaminated Soil with Green Surfactant Using a Mobile Remediation System

Leak of fuels and lubricants occurring during exploration, distribution, refining and storage operations is the major cause of environmental pollution due to petroderivatives dispersion. The quick use of a series of physicochemical and biological techniques is needed to drastically reduce the magnitude of damage provoked by these pollutants. Among them, soil washing proved to be an effective alternative to the remediation of hydrocarbon-polluted sites, mainly if combined with surfactant utilization. However, the direct use of surfactants can lead to problems related to the toxicity and dispersion of the resulting by-products, as the majority of marketed surfactants are produced from oil derivatives. In this context, green surfactants appear as a promising alternative to their synthetic counterpart. In the present study, two green surfactants, i.e., a chemically synthesized biobased surfactant and a Starmerella bombicola biosurfactant, were applied in soil decontamination tests using a concrete mixer-type Mobile Soil Remediation System (MSRS). The system was designed and developed with 3D printing based on bench-scale results. A commercial biosurfactant was formulated based on the microbial surfactant, which was compared with the biobased surfactant in various experimental conditions. A set of factorial designs combined with Response Surface Methodology was used to select the optimal conditions for pollutant removal using the prototype. The following variables were tested: Surfactant type, Surfactant volume, Surfactant dilution, Contaminant concentration, Soil type, Soil mass, Washing duration, Tank tilt angle, Mixing speed, and Type of basket. Under the optimized experimental condition, the commercial biosurfactant allowed to remove 92.4% of the motor oil adsorbed in the sand. These results demonstrate the possibility of using natural surfactants and the development of novel mechanical technologies to degrade hydrocarbons with economic earnings for oil industry.

Heavy Metal Tolerance profile among Bacterial species Isolated from Hydrocarbon polluted sites and their mobile genetic elements

This present study evaluated the plasmid incidence in bacteria and their genetic elements in heavy metals tolerant-antibiotics resistant microbes isolated from petroleum hydrocarbon polluted sites. The plasmid isolation was carried out using the fermentas Genejet plasmid miniprep kit (Thermofisher Scientific Inc, USA). Screening for class 1, 2, and 3 integrons, incompatibility group P testing, plasmid replicon typing, plasmid restriction analysis, and other analysis was performed using standard laboratory procedures. Plasmid incidences were higher among multiple heavy metal-tolerant bacterial species from hydrocarbon-polluted sites than those from the pristine site. Further, Class 1 integron incidence was significantly higher among the integrons in heavy metal tolerant bacterial isolates isolated from the polluted ecosystems than those from pristine ecosystems. Plasmid replicon type of bacteria with multiple heavy metal tolerance and antibiotics resistance indexes revealed that IncN plasmid replicon type carrying class 1 integron. This encodes resistance to sulphamethazole/trimethoprim, ampicillin, and tolerance to Cd, Ni, and Cu in Klebsiella pneumoniae isolate from petroleum-polluted soil. This is the first report of IncN plasmid in environmental bacteria in Nigeria, particularly from petroleum polluted environment. The conjugation experiment confirmed the possible transferability of antibiotic resistance determinants among isolates in polluted ecosystems. From the results of this study, it can be concluded that petroleum hydrocarbon pollution vis-a-vis heavy metal selective pressure with the abundance of mobile genetic elements amongst isolates from polluted ecosystems could contribute to the dispersing of antibiotic resistance genes, thus posing a serious public health concern.

Structure of the lipopolysaccharide O-antigen of Serratia spp. strains 10.1WK and 1XS plant endophytes isolated from O. biennis and L. corniculatus

O-specific polysaccharides (O-PSs) isolated from lipopolysaccharides of Serratia spp., strains 10.1WK and 1XS, which are endophytic bacteria of Oenothera biennis (common evening-primrose) and Lotus corniculatus (bird's-foot trefoil), plants growing on a petroleum hydrocarbon polluted site in the Silesia region, were investigated. The high-molecular-weight O-PS fractions liberated from lipopolysaccharides by mild acid hydrolysis were studied using chemical methods, MALDI-TOF mass spectrometry, and a set of 1D and 2D NMR spectroscopy techniques. It was found that both O-specific polysaccharides were built of an identical trisaccharide repeating unit composed of d-Rhap and d-Manp residues. The following structure of the O-PSs of Serratia spp. strains 10.1WK and 1XS was established:→4)-α-d-Rhap-(1 → 3)-β-d-Manp-(1 → 4)-β-d-Rhap–(1→

Synthetic Saccharomyces cerevisiae tolerate and degrade highly pollutant complex hydrocarbon mixture

Fungal laccase (Lac) has become a very useful biocatalyst in different industries, bio-refineries and, most importantly, bioremediation. Many reports have also linked hydrocarbon tolerance and degradation by various microorganisms with Lac secretion. In this study, Trametes trogii Lac (Ttlcc1) was engineered into Saccharomyces cerevisiae strain CEN.PK2–1 C under the constitutive GPD promoter (pGPD) for multi-fold synthesis with efficient hydrocarbon tolerance and degradation. Protein expression in heterologous hosts is strictly strain-specific, it can also be influenced by the synthetic design and culture conditions. We compared synthetic designs with different shuttle vectors for the yeast strains and investigated the best culture conditions by varying the pH, temperature, carbon, nitrogen sources, and CuSO4 amount. Two S. cerevisiae strains were built in this study: byMM935 and byMM938. They carry the transcription unit pGPD-Ttlcc1-CYC1t either inside the pRSII406 integrative plasmid (byMM935) or the pRSII426 multicopy plasmid (byMM938). The performance of these two synthetic strains were studied by comparing them to the wild-type strain (byMM584). Both byMM935 and byMM938 showed significant response to different carbon sources (glucose, galactose, lactose, maltose, and sucrose), nitrogen sources (NH4Cl, NH4NO3, KNO3, malt extract, peptone, and yeast extract), and solid state fermentation of different plant biomasses (bagasse, banana peels, corn cob, mandarin peels, and peanut shells). They performed best in optimized growth conditions with specific carbon and nitrogen sources, and a preferred pH in the range 3.5–4.5, temperature between 30 and 40 0C, and 1 mM CuSO4. In optimized yeast-growth medium, strain byMM935 showed the highest laccase activities of 1.621 ± 0.063 U/mL at 64 h, whereas byMM938 gave its highest activity (1.417 ± 0.055 U/mL) at 48 h. In this work, we established, by using Bushnell Hass synthetic medium, that the new Ttlcc1-yeast strains tolerated extreme pH and complex hydrocarbon mixture (CHM) toxicity. They degraded 60–90% of the key components in CHM within 48 h, including poly-cyclic aromatic hydrocarbons, alkyl indenes, alkyl tetralines, alkyl benzenes, alkyl biphenyls, and BTEX (Benzene, Toluene, Ethylbenzene, and Xylenes). This is the first report on the hydrocarbon degradation potential of a Ttlcc1-yeast. Compared to the native organism, such synthetic strains are better suited for meeting growing demands and have potentials for application in large-scale in situ bioremediation of hydrocarbon-polluted sites.

Biodegradation of Escravos light crude oil by three indigenous bacteria, isolated from mechanic workshop in Lagos State Nigeria

Introduction: Petroleum hydrocarbons can be degraded by microorganisms such as bacteria, fungi, yeast and microalgae. However, bacteria play an imperative role in hydrocarbon degradation. Microorganisms are endowed with metabolism machinery to use petroleum products as a carbon and energy source Aims: The aim of the study is to isolate hydrocarbon degrading bacteria from hydrocarbon polluted site (mechanic workshops) in Lagos state. Materials and Methods: The physical, chemical and microbiological properties of the three soil sample were analyzed using standard procedure. Hydrocarbon degraders were isolated on 1% crude oil mineral salt medium via enrichment technique. The best hydrocarbon degrader were identified on the basis of their colonial morphology, biochemical characteristics and complemented with analytical profile index (API) kit. Hydrocarbon degradation were monitored using total viable count and residual oil was determined by Gas Chromatography equipped with Flame Ionized detector (GC-FID). Results: Alkaline pH were observed for all three soil samples, the total nitrogen detected were 0.07, 0.04 and 0.1. The total heterotrophic bacteria (THB) estimated were 3 x 1010, 6.5 x 109 and 1.7 x 1010 cfu/ml while the total hydrocarbon utilizing bacteria estimated via vapour phase were 1.89 x 106 , 4x104 and 9.62 x 107 cfu/ml for Ikeja, Iyana-Iba and Mushin sample. The organisms had a generation time of 5.56, 9.09 and 10.9 (d), the degradation half-life were 3.85, 6.3 and 7.5 (d) respectively. Over 60% hydrocarbon degradation were determined within 10 days for all three isolates. The Gc-fid prints shows reduction in peak area of various hydrocarbon fractions with a decrease in pH of the medium. Conclusion: The study showed that hydrocarbon degraders are ubiquitously distributed in the hydrocarbon polluted soil sample. Their degradation potential can be optimized so as curtail the adverse effect of petroleum in the environment

In-situ remediation of petroleum-contaminated soil by application of plant-based surfactants toward preventing environmental degradation

Remediation in this study employs the use of green plants and their extracts in enhancing the remediation process of polluted soils. GC-MS & FTIR techniques were employed in determining the constituents of the soil during the investigation. 60 ml of the extracts were applied on 1 by 2 ft segments of hydrocarbon polluted site and observed for two months. The results show that plant extract A significantly reduced the TPHs and PAHs to 5,450 and 126.2 mg/kg, respectively, as compared to those of extract B whose TPH and PAH values are 10,432 and 362.3 mg/kg, respectively. Both plant extracts reduced the total petroleum hydrocarbon compounds significantly when compared to the standard reference PAH and PAHs (4,500 mg/kg and 50 mg/kg respectively). The microbial plate count for the three media shows that the plant based surfactant had a synergy with the identified bacteria in enhancing Phytoremediation of the crude oil polluted site. Novelty statement: This study examined the application of two plant-based surfactants for remediation. These natural surfactants significantly reduced the petroleum hydrocarbon compounds present in the soil within the in-situ observation window. These Herbaceous plant family extracts have a great advantage as an eco-friendly alternative to synthetic surfactants, and they also exhibited an anti-fungi characteristic. The two biodegradable plant-based surfactants also significantly reduced the time that it could have taken for a remediation process.

Isolation and Characterization of Carbonoclastic Bacteria Diversity in Oil-contaminated Soil in Cape Coast Metropolis, Ghana

Aims: The study aimed at the quantification, isolation and characterization of hydrocarbon degrading bacteria in oil-contaminated and pristine soils.
 Methodology: Soil samples from petroleum hydrocarbon polluted sites at auto-mechanic workshops, a mechanic village, as well as pristine (control) soils, comprising of 14 sampling locations within Cape Coast Metropolis in the Central Region of Ghana were collected using standard sampling techniques. Collected soil samples were treated and cultured while enumerations, isolations and characterization of carbonoclastic bacteria associated were evaluated.
 Results: Bacterial populations isolated from hydrocarbon-polluted sites had higher aerobic counts ranging from 7.24-8.02 log10 cfu/g of soil when compared with the pristine sites (from 6.79-7.61 log10 cfu/g of soil). Also, soil samples from the mechanic village (8.76 to 7.48 log10 cfu/g of soil) recorded more bacterial counts than those from the mechanic garages (8.02 to 7.24 log10 cfu/g of soil). The calculated percentage profiles of all the hydrocarbon utilizing bacteria in the total culturable heterotrophic bacteria were low throughout the study, even though the percentage scores were all above 50%. A total of 19 hydrocarbon degraders were isolated. The isolates identified belong to the genera Pseudomonas, Proteus, Bacillus and Enterobacter.
 Conclusion: The outcome of the study based on the bacteria populations, identification profiles, coupled with their survival and multiplications in designated medium amended with crude oil as the carbon and energy sources, suggest their petroleum hydrocarbon degrading capabilities, hence may be used in bioremediation applications.

Analysis of viral and bacterial communities in groundwater associated with contaminated land

This work aimed at the comprehensive analysis of total microbial communities inhabiting a typical hydrocarbon-polluted site, where chemical characteristics of the groundwater were readily available. To achieve this, a joint metagenomic characterization of bacteria and viruses surrounding a contaminant plume was performed over a one-year period. The results presented demonstrated that both potential hydrocarbon degraders and their bacteriophages were dominant around the plume, and that the viral and bacterial diversities found at the site were probably influenced by the pH of the groundwater. Niche-specific and dispersed associations between phages and bacteria were identified. The niche phage-host associations were found at the edge of the site and at the core of the plume where pH was the highest (9.52). The identified host populations included several classes of bacteria (e.g. Clostridia and Proteobacteria). Thirty-six viral generalists were also discovered, with BGW-G9 having the broadest host range across 23 taxa, including Pseudomonas, Polycyclovorans, Methylocaldum and Candidatus Magnetobacterium species. The phages with broad host ranges are presumed to have significant effects on prokaryotic production and horizontal gene transfer, and therefore impact the biodegradation processes conducted by various bacteria of the environment studied. This study for the first time characterized the phages and their bacterial hosts associated with a contaminant plume.

English

This study examined the application of the Analytic Network Process (ANP), a multi-criteria decision analysis tool, in the selection of the best bioremediation technique for the remediation of a hydrocarbon-polluted site at Kwawa (4°36'29.26''N, 7°28'55.70''E) in Ogoniland, Niger Delta province, Nigeria. The decision-making problem involved four bioremediation techniques (that is, landfarming, field biopiles, thermal desorption, and phytoremediation) as well as four selection criteria (that is, health and safety, technical feasibility, regulatory requirements, and site-specific characteristics) and their twelve selection sub-criteria. The ANP evaluation involved pairwise comparisons of the remediation alternatives, selection criteria, and selection sub-criteria. Judgement matrices including unweighted supermatrix, weighted supermatrix, and a limit matrix were developed. The alternative with the highest priority vector at convergence was selected as the best. Result showed that phytoremediation with the highest priority vector of 0.1054 was the most appropriate remediation alternative for the study site. Additionally, site-specific characteristics with highest priority vector of 0.1636 was the most important selection criteria while type of soil with highest priority vector of 0.0625 was the most influential selection sub-criterion for the study site. This suggests that the ANP promises to be a veritable decision-support tool for the selection of the most appropriate bioremediation method for petroleum-contaminated sites in the Niger Delta province, Nigeria. Key words: Multi-criteria decision analysis, land contamination, bioremediation.

Floristic surveys of hydrocarbon-polluted sites in some Cameroonian cities (Central Africa)

ABSTRACTSoils pollution with hydrocarbons is on the increase, especially in developing countries like Cameroon. Identifying plant species capable of growing on hydrocarbon-polluted soils remains an essential step in phytoremediation, a low cost, solar energy driven clean up technique in which living green plants are used. Here, we report floristic surveys conducted in 4 cities of Cameroon to identify plants with phytoremediation capacities. A total of 13 hydrocarbon-polluted sites were surveyed in each city using the quadrat method. Unpolluted sites served as the control. 106 species belonging to 76 genera and 30 families were identified on hydrocarbon-polluted sites. Plant diversity was shown to be higher (166 species contained in 125 genera and 50 families) in the control sites. Poaceae, Cyperaceae, Asteraceae and Amaranthaceae families have a higher taxonomic richness on polluted sites (16, 15, 10 and 8 taxa respectively). Shannon diversity index of the hydrocarbon-polluted sites (1.6 to 2.7 bits/ind.) were significantly lower than the control sites (2.7 to 3.2 bit/ind.). Based on a relative frequency > 10% and abundance > 7%, our results show that more than 15 plant species could be tested in preliminary trials to determine their phytoremediation/cleaning-up capacities on hydrocarbon-polluted soils in the tropics.

Hydrocarbon degradation potential and plant growth-promoting activity of culturable endophytic bacteria of Lotus corniculatus and Oenothera biennis from a long-term polluted site

Many endophytic bacteria exert beneficial effects on their host, but still little is known about the bacteria associated with plants growing in areas heavily polluted by hydrocarbons. The aim of the study was characterization of culturable hydrocarbon-degrading endophytic bacteria associated with Lotus corniculatus L. and Oenothera biennis L. collected in long-term petroleum hydrocarbon-polluted site using culture-dependent and molecular approaches. A total of 26 hydrocarbon-degrading endophytes from these plants were isolated. Phylogenetic analyses classified the isolates into the phyla Proteobacteria and Actinobacteria. The majority of strains belonged to the genera Rhizobium, Pseudomonas, Stenotrophomonas, and Rhodococcus. More than 90% of the isolates could grow on medium with diesel oil, approximately 20% could use n-hexadecane as a sole carbon and energy source. PCR analysis revealed that 40% of the isolates possessed the P450 gene encoding for cytochrome P450-type alkane hydroxylase (CYP153). In in vitro tests, all endophytic strains demonstrated a wide range of plant growth-promoting traits such as production of indole-3-acetic acid, hydrogen cyanide, siderophores, and phosphate solubilization. More than 40% of the bacteria carried the gene encoding for the 1-aminocyclopropane-1-carboxylic acid deaminase (acdS). Our study shows that the diversity of endophytic bacterial communities in tested plants was different. The results revealed also that the investigated plants were colonized by endophytic bacteria possessing plant growth-promoting features and a clear potential to degrade hydrocarbons. The properties of isolated endophytes indicate that they have the high potential to improve phytoremediation of petroleum hydrocarbon-polluted soils.

Comparative Activities of Soil Enzymes from Polluted Sites in Egbema, Imo State, Nigeria

The levels of activities of dehydrogenase, hydrogen peroxidase, catalase and lipase of different soil strata from hydrocarbon polluted site (HCPS), domestic waste polluted site (DWPS) and palm oil mill effluent polluted site (POMEPS) as well as unpolluted site were evaluated. Soil samples, namely, subsoil from 50 cm below soil surface, and topsoil were collected from different locations in Egbema urban area in Ohaji/Egbema local government area of Imo state, Nigeria. Soil enzymes activities were measured using spectrophotometric and titrimetric methods. Dehydrogenase activities of topsoil and subsoil from POMEPS were significantly (p<0.05) higher than those from unpolluted site. Comparative analysis of soil enzyme activity showed that topsoil and subsoil from HCPS gave the highest hydrogen peroxidase activity of 8.48 ± 0.01 × 10-3 U/g and 7.52 ± 0.02 × 10-3 U/g respectively. Topsoil from POMEPS gave the highest lipase activity of 1.90 ± 0.02 U/g and was followed by lipase activity of subsoil from DWPS=1.85 ± 0.02 U/g. Catalase activity of the subsoil was significantly (p<0.05) higher than that of the topsoil from all soil sites. The overall variability in enzymes activities of soil strata from different polluted sites defined the pattern of soil contamination, which could serve as biomarkers for ascertaining level of soil pollution as well as monitorial indices for bioremediation.

The impact of long-term hydrocarbon exposure on the structure, activity, and biogeochemical functioning of microbial mats

Photosynthetic microbial mats are metabolically structured systems driven by solar light. They are ubiquitous and can grow in hydrocarbon-polluted sites. Our aim is to determine the impact of chronic hydrocarbon contamination on the structure, activity, and functioning of a microbial mat. We compared it to an uncontaminated mat harboring similar geochemical characteristics. The mats were sampled in spring and fall for 2years. Seasonal variations were observed for the reference mat: sulfur cycle-related bacteria dominated spring samples, while Cyanobacteria dominated in autumn. The contaminated mat showed minor seasonal variation; a progressive increase of Cyanobacteria was noticed, indicating a perturbation of the classical seasonal behavior. Hydrocarbon content was the main factor explaining the differences in the microbial community structure; however, hydrocarbonoclastic bacteria were among rare or transient Operational Taxonomic Units (OTUs) in the contaminated mat. We suggest that in long-term contaminated systems, hydrocarbonoclastic bacteria cannot be considered a sentinel of contamination.

Pyrene metabolism by the novel bacterial strains Burkholderia fungorum (T3A13001) and Caulobacter sp (T2A12002) isolated from an oil-polluted site in the Arabian Gulf

The novel bacterial strains Burkholderia fungorum T3A13001 and Caulobacter sp T2A12002, which were previously isolated from oil-contaminated sites and identified via 16S RNA sequences, were tested for their hydrocarbon degrading efficiency. Media spiked with 100 ppm pyrene were incubated at 25 °C and 37 °C. The bacterial isolates' pyrene-degrading capability was assessed in acidic (pH 5.0) and alkaline (pH 9.0) media. Caulobacter sp degraded 21% and 24% of the pyrene at pH 9.0 and 5.0, respectively; thus, the strain was more active at pH 5.0 than pH 9.0. B. fungorum was active in a wide range of pH values, because it biodegraded 59%–62% of the provided pyrene in acidic and alkaline media. Caulobacter sp degraded 35%–36% of the provided pyrene in cultures at 37 °C and 25 °C. B. fungorum degraded 56% and 59% of the provided pyrene at 37 °C and 25 °C, respectively. Given that B. fungorum biodegraded over the half-life of the initial 100 ppm pyrene in the cultures, the strain may be suitable for bioremediation of high molecular weight PAHs. The study provides important insight into possible PAH biodegradation and bioremediation of hydrocarbon-polluted sites using novel bacterial strains.

Enhanced Degradation of Petroleum Hydrocarbons in Corn-Steep-Liquor-Treated Soil Microcosm

The efficiency of corn steep liquor (CSL) as a potential stimulant for remediation of hydrocarbon-contaminated soil was evaluated in soil microcosms. Chronically polluted soil samples treated with CSL, water, and un untreated control were compared over a period of 42 days. There were remarkable changes in the physicochemical status of the soil in the CSL-treated set-up with noticeable utilization of essential nutrients such as nitrogen, phosphorus, and potassium. Percentage hydrocarbon utilizers showed a concomitant increase with hydrocarbon utilization in CSL-treated (0.05–0.16%) and water-treated (0.02–0.12%) set-ups, while no significant changes occurred in the untreated control. Gas chromatographic fingerprints showed complete disappearance of the lower-fraction alkanes C7, C8, C9, and C11 within 21 days, as well as some higher fractions, significantly C16 and C29, in the CSL-treated set-up. In the CSL-treated set-up, 77.9% of hydrocarbon was degraded, while the corresponding values for the water-treated and untreated control were 40.55 and 30.6%, respectively. The percentage aliphatic components degraded differed significantly in the CSL-treated, water-treated, and untreated set-ups. The n-C17/pristane and n-C18/phytane ratios in the CSL-treated set-up were 1.298 and 1.153, respectively, on day 0, but at the end of the treatability period, the values had dropped drastically to 0.182 and 0.585, respectively. The results of this study show that corn steep liquor is a potential material for bioremediation of hydrocarbon-polluted sites.

Determination of migration rates of contaminants in a hydrocarbon-polluted site using non-reactive tracer test in the Niger Delta, Nigeria

A natural gradient tracer test with sodium chloride as the injectate was conducted using one injection well and eleven observation wells in an oil-contaminated site in the study area. The aim was to characterize the site and to determine migration rates of the contaminants to provide information on their fate in groundwater resources in the area. The migration of the tracer was constantly monitored by sampling all the observation wells spaced 5 m from each other at 15–30 min intervals for a period of 6 days. The test soil layer is a clayey silty sand consisting of 50 % sand, 30 % silt and 20 % clay. The average static water level at the site is about 2.5 m. Gas chromatography fingerprinting showed that kerosene and diesel are the dominant fractions within the soil matrix. The arrival times of the breakthrough moments of the migrating tracer plume from two observation piezometers situated 2.0 and 7.22 m away from the injection well showed that the mean velocity in the longitudinal direction in the aquifer is 1.403 × 10−3 ms−1 (121 m/day). The longitudinal and transverse dispersion coefficients of 2.45 × 10−3 m2s−1 and 2.3 × 10−3 m2s−1 were used to obtain longitudinal and transverse dispersivities of 1.78 and 1.64 m, respectively. High hydraulic conductivity denoted by the high migration rate of the tracer implies that contaminant at the site will migrate through the aquifer with relative ease. However, the significant clay fraction within the soil provides the medium for adsorption and partitioning of contaminants to the soil.

Isolation and Screening of Black Fungi as Degraders of Volatile Aromatic Hydrocarbons

Black fungi reported as degraders of volatile aromatic compounds were isolated from hydrocarbon-polluted sites and indoor environments. Several of the species encountered are known opportunistic pathogens or are closely related to pathogenic species causing severe mycoses, among which are neurological infections in immunocompetent individuals. Given the scale of the problem of environmental pollution and the phylogenetic relation of aromate-degrading black fungi with pathogenic siblings, it is of great interest to select strains able to mineralize these substrates efficiently without any risk for public health. Fifty-six black strains were obtained from human-made environments rich in hydrocarbons (gasoline car tanks, washing machine soap dispensers) after enrichment with some phenolic intermediates of toluene and styrene fungal metabolism. Based on ITS sequencing identification, the majority of the obtained isolates were members of the genus Exophiala. Exophiala xenobiotica was found to be the dominant black yeast present in the car gasoline tanks. A higher biodiversity, with three Exophiala species, was found in soap dispensers of washing machines. Strains obtained were screened using a 2,6-dichlorophenol-indophenol (DCPIP) assay, optimized for black fungi, to assess their potential ability to degrade toluene. Seven out of twenty strains tested were able to use toluene as carbon source.

Bioremediation of diesel-polluted soil using biostimulation as post-treatment after oxidation with Fenton-like reagents: Assays in a pilot plant

The present study focuses on the remediation of diesel-polluted soil using modified Fenton treatment coupled with inorganic NPK fertilizer (“Fenton+NPK”). Studies were carried out in a pilot plant containing 1m3 of sandy soil contaminated with 20,000mgkg−1 of diesel, placed outdoors at a temperature ranging between 5 and 10°C. Results showed that NPK-fertilizer as post-treatment stimulated culturable degrading bacteria and enhanced dehydrogenase activity. Fenton+NPK treatment increased total petroleum hydrocarbon (TPH) removal efficacy. Natural attenuation removed 49% of TPH in the surface layer, 23% of TPH in the non-saturated layer and 4% of the TPH in the saturated layer, while the percentage removed of TPH after Fenton+NPK treatment was 58%, 57% and 32% respectively. The results from our study showed that, immediately after soil contamination, occurred a specialization and differentiation of the bacterial community, but after this initial modification, no significant changes of bacterial diversity was observed under natural attenuation conditions. In contrast, when the Fenton's reagent was applied a reduction of the bacterial biodiversity was observed. However, the post-biostimulation did enhance the degrading microbiota and stimulated their degrading biological activity. In conclusion, biostimulation, as a post-treatment step in chemical oxidation, is an effective solution to remediate hydrocarbon-polluted sites.