Remediation Of Crude Oil-contaminated Soil Research Articles

Feasibility of microwave remediation of simulative crude oil-contaminated soil assisted by bluecoke-based modifiers

Microwave (MW) remediation of organics-contaminated soil technology offers the advantages of high efficiency and minimal damage, representing a new approach of soil thermal remediation. However, soil, being a weak MW-absorbing medium, struggles to convert MW energy into thermal energy, thus failing to attain the necessary temperature for thermal remediation. This paper prepared two new bluecoke (BC)-based modifiers (KHCO3@BC and KHCO3/MnO2@BC) to address temperature problem of MW remediation, as well as enhance soil quality. Their composition, structure and electromagnetic properties were analyzed to investigate their role in assisting with the MW remediation of an artificially crude oil-contaminated soil were investigated. Additionally, the industrial feasibility of MW remediation was addressed for the first time. The results showed that the KHCO3 and MnO2 particles in the two modifiers were covered on the BC surface and exhibited local agglomeration. Their carbon crystalline grain size increased, and the electromagnetic properties were weaker than those of the BC. Following 10 min of MW remediation assisted by KBC or KMnBC, the remediation temperatures exceeded 300 °C, with the removal rates of PHs reaching 76.16% and 88.31%, respectively. The organic matter content, soil potassium and mechanical fraction of the remediated soil were improved, but soil acidification still needed to be further addressed. The industrial application analysis indicated that the technical process and techno-economics of MW remediation of crude oil-contaminated soil were feasible, suggesting significant potential for the large-scale industrial application.

Modelling of Bioremediation of Oil-Contaminated Soil Using Chicken Droppings as Biostimulant

The suitability of poultry droppings as a biostimulant for the remediation of crude oil-contaminated soil has been investigated. Four equal-sized containers, each containing 400g of soil were each contaminated 20 ml of crude oil after which they were thoroughly mixed. To first three containers, A,B and C were respectively added 20 g, 60 and 100 g of poultry droppings which were previously dried and pulverised. To the fourth container which served as control, was added no poultry droppings. The degradation of oil in the samples were monitored for 7 weeks by observing the residual hydrocarbon content (RHC) and pH of samples. The RHC of the samples over the seven-week period were then modelled using artificial neural network (ANN) in the MATLAB Neural Network Toolbox. The RHC values decreased for all samples, with the highest reduction of 100 mg/kg obtained in sample C and the least reduction of 1000 mg/kg in sample D. The PH values were observed to increase slightly from the acidic region of 5.5 to a range of 7.8 to 8.3. The best and most suitable training algorithm of RHC of the samples was TRAINSCG since it had the least mean square error (MSE) value of 0.00183 as well as the highest R-squared value of 0.99808.

Bioremediation of Crude Oil-Contaminated Soil using Compost as Bio-Stimulant

This study was conducted to investigate the usability of compost as a stimulant for the remediation of crude oil-contaminated soil. 2kg of porous sandy soil was measured into six different equal-sized cells and contaminated with 250 ml of sample crude oil. Masses of solid waste comprising of compost and sawdust were measured in varying amounts of 900g, 750g, 600g, 450g, 300g, and a control sample that had no compost and sawdust. The set-up was left to stand for eight weeks and the residual hydrocarbon content (RHC), pH, and total microbial count (TMC)of these samples were monitored and recorded. The percentage of hydrocarbon degradation that occurred in the treatment cells were; 33.11, 32.2, 31.2, 29.46 and 28.05 respectively, for the individual cells in the order above, while the control had a degradation rate of (0.44%) of the total hydrocarbon content after 8 weeks. pH values varied slightly within the ranges of 6.5-7.5. The TMC average values were 21, 188, 17,125, 15,000, 14,250, 13,125 and 0.1, with the highest count occurring in the sample having 900g of solid waste; followed by the other samples having lesser quantities of solid waste with the least value in the control. The resultant descent in TMC across each of the samples was due to the distribution of waste material in the samples, and the pH of the resulting mixtures remained at optimum, thereby favouring microbial growth across the samples.

Development of a plant microbiome bioremediation system for crude oil contamination

Bacterial-assisted phytoremediation is recently being considered to be an efficient technique for remediation of crude oil-contaminated soil. The present research was designed to establish a plant microbiome bioremediation system for treating crude oil contamination. 10 strains of plant growth-promoting rhizobacteria (PGPR) were isolated from oil-contaminated soil near Oil Refinery Rawalpindi, Pakistan. Based on plant growth-promoting characteristics and biosurfactant production, two strains (Pseudoarthrobacter phenanthrenivorans (MS2) and Azospirillum oryzae (MS6)) were selected. They showed a better emulsification index (54.2, 42.5%), oil displacement activity (3.4, 2.6 mm), and hydrophobicity content (78, 75%,). For the establishment of the plant microbiome system, both strains and their combination were inoculated in rhizospheric soil of maize in crude oil-contaminated soil. Better germination attributes of maize were observed by a combination of both strains with improved fresh (32%) and dry biomass (26.5%) as compared to control under oil stress (10%). Plant microbiome bioremediation system improved the chlorophyll content (30.4%), water potential (23.2%), proline (32%), amino acids (11.1%), and antioxidant enzymes (catalase (21%), peroxidase dismutase (30%) and superoxide dismutase (22%), as compared to control under oil stress (10%). The hydrocarbons degradation efficiency of this system was 38.5%. Analysis of degradation products by GC-MS revealed the presence of low molecular weight hydrocarbons in the treated soil as compared to untreated soil. This study showed promising results by this plant microbiome system can be a way forward in bacterial assisted phytoremediation approaches at the field level in the future.

Biostimulation potential of biochar for remediating the crude oil contaminated soil and plant growth.

Crude oil contamination is a serious environmental threat to soil and plants growing in it. Biochar has the potential of biostimulation for remediation of crude oil-contaminated soil. Therefore, the current research was designed to analyze the bio-stimulatory impact of biochar for remediating the crude oil contaminated soil (10%, and 15%), and growth of maize under glasshouse conditions. Biochar was produced by pyrolysis of Australian pines at 350 °C. Soil incubations were done for 20 days. The results of soil analysis showed that the crude oil degradation efficiency of biochar was 34%. The soil enzymatic activities had shown 38.5% increase in fluorescein diacetate (FDA) hydrolysis and 55.6% increase in dehydrogenase activity in soil incubated with biochar in comparison to control. The soil microbial diversity was improved to 41% in biochar treated soil with respect to untreated one, while microbial respiration rate had shown a 33.67% increase in soil incubated with biochar with respect to control under oil stress. Gas Chromatography Mass spectrometry (GC-MS) analysis had shown the high content of low molecular weight hydrocarbons (C9-C13) in the soil incubated with biochar in comparison to untreated soil. Biochar showed a significant increase in fresh and dry biomass (25%, 14.61%), leaf area (10%), total chlorophyll (11%), water potential (21.6%), osmotic potential (21%), and membrane stability index (12.7%). Moreover, biochar treatment showed a higher increase in the contents of proline (29%), total amino acids (18%), soluble sugars (30.4%), and antioxidant enzymes like superoxide dismutase (16.5%), catalase (11%), and peroxidase (12%). Overall, the results of the present study suggest the bio-stimulating potential of biochar for degradation of hydrocarbons in crude oil contaminated soil and their growth-stimulating effects on maize.

Pyrolytic remediation of crude oil-contaminated soil

Deterioration of our terrestrial environment due to decreasing soil quality brought on by crude oil spills and leakages is a major issue. In this study, soil samples were prepared by mixing clay (bentonite) and sand contaminated with 5 and 10 wt% crude oil (in order to study the effect of oil concentration), and weathered in a laboratory to simulate actual contaminated soil. Volatilization of light oil was inhibited in clay rich-soil, resulting in higher contamination after weathering. The efficiency of the pyrolytic treatment was evaluated by comparing the weight change and n-hexane extractable material (HEM) content of the soil samples. The working temperature influenced pyrolysis efficiency more than the reaction time. A residual amount of 0.29–0.61 wt% (below the soil pollution standard) was observed in the samples with high clay content and pollution level (by pyrolysis for 30 min at 400 °C). Infrared analysis of treated soil samples showed a reduction in alkyl functionality (CH), confirming a decrease in hydrophobicity and an improvement in water holding capacity (WHC). Seed germination and plant growth were relatively better in the pyrolyzed soil. The field applicability of the pyrolytic treatment process was confirmed at laboratory and pilot scale, as well as by treating soil samples collected from actual polluted sites.

Interactions between electrokinetics and rhizoremediation on the remediation of crude oil-contaminated soil

An electrokinetics (EK)-enhanced phytoremediation system with ryegrass was constructed to remediate crude oil-polluted soil. The four treatments employed in this study included (1) without EK or ryegrass (CK-NR), (2) EK only (EK-NR), (3) ryegrass only (CK-R), and (4) EK and ryegrass (EK-R). After 30d of ryegrass growth, EK at 1.0 V·cm−1 with polarity reversal (PR-EK) was supplied for another 30 d. The electric current was recorded during remediation. The pH, electrical conductivity, total petroleum hydrocarbon content (TPH), 16S rDNA, functional genes of AlkB, Nah, and Phe, DGGE, and dehydrogenase activity in soil were measured. The physical-chemical indexes of the plant included the length, dry mass, and chlorophyll contents of the ryegrass. Results showed that EK-R removed 18.53 ± 0.53% of TPH, which was higher than that of other treatments (13.34–14.31%). Meanwhile, the values of 16S rDNA, AlkB, Nah, Phe, and dehydrogenase activity in the bulk soil of EK-R all increased. Further clustering analysis with numbers of genes and DGGE demonstrated that EK-R was similar to the ryegrass rhizosphere soils in both EK-R and CK-R, while the EK treatment of EK-NR was similar to that of CK-NR without EK and ryegrass. These results indicate that the PR-EK treatment used in this experiment successfully enlarged the existing scale of the rhizosphere microorganisms, improved microbial activity and enhanced degradation of TPH.

Efficient remediation of crude oil-contaminated soil using a solvent/surfactant system.

Crude oil contaminated soil has been widely recognized to constitute a major environmental issue due its adverse effects on human health and ecological safety. The main objective of this study is to explore the possibility of using an ex situ solvent/surfactant washing technique for the remediation of crude oil-contaminated soil. Three organic solvents (methanol, acetone, and toluene) and one surfactant (AES-D-OA) were employed to form three kinds of solvent/surfactant systems, and utilized to evaluate the desorption performance of crude oil from soil. Natural soil, crude oil-contaminated soil, and after-remediation soil were characterized by SEM, EDX, FT-IR, and contact angle. The ability of solvent/surfactant systems to remove crude oil from soil was determined as a function of solvent polarity, mass ratio of solvent to surfactant, temperature, and ionic strength. The removal of crude oil by the toluene/AES-D-OA system was found to be more effective than the other systems. At a high toluene ratio, more than 97% of crude oil could be removed from contaminated soil. Crude oil removal efficiency was also found to increase with rising temperature or increasing ionic strength appropriately. Experimental results suggested that, compared to conventional surfactant-aided remediation, the combined utilization of surfactant and solvent achieved superior results for crude oil removal because of their similar compositions and structures in terms of aromaticity and polarity.

Successful phytoremediation of crude-oil contaminated soil at an oil exploration and production company by plants-bacterial synergism

ABSTRACTPhytoremediation is a promising approach for the cleanup of soil contaminated with petroleum hydrocarbons. This study aimed to develop plant-bacterial synergism for the successful remediation of crude oil-contaminated soil. A consortia of three endophytic bacteria was augmented to two grasses, Leptochloa fusca and Brachiaria mutica, grown in oil-contaminated soil (46.8 g oil kg−1 soil) in the vicinity of an oil exploration and production company. Endophytes augmentation improved plant growth, crude oil degradation, and soil health. Maximum oil degradation (80%) was achieved with B. mutica plants augmented with the endophytes and it was significantly (P < 0.05) higher than the use of plants or bacteria individually. Moreover, endophytes showed more persistence, the abundance and expression of alkB gene in the rhizosphere as well as in the endosphere of the tested plants than in unvegetated soil. A positive relationship (r = 0.70) observed between gene expression and crude oil reduction indicates that catabolic gene expression is important for hydrocarbon mineralization. This investigation showed that the use of endophytes with appropriate plant is an effective strategy for the cleanup of oil-contaminated soil under field conditions.

Role of hemoglobin in hemoglobin-based remediation of the crude oil-contaminated soil

This study investigated the changes in the indigenous microbial community structure with hemoglobin (Hb) application to determine the role of Hb in Hb-based remediation of crude oil-contaminated soil. The phylogenetic diversity of the bacterial community showed that the Hb addition selected surfactants-producing species, thereby, promoting TPH degradation. The significant increase in the CO2 generation, which can be related to the increase in the bacterial abundance inferred from the 16S rRNA gene copy number, supports the enhanced TPH degradation with Hb application. The similar residual TPH concentrations in the presence of only hydrogen peroxide (H2O2) and both Hb and H2O2 suggested that the role of Hb as a catalyst was not as significant as the role of Hb as a nutrient. Also, in the presence of H2O2, a greater recovery of the microbial community structure was observed with the double Hb injection than the single Hb injection. Overall, this study shows that the Hb-based remediation strategies via microbial metabolism can be successfully applied to remediate the crude-oil contaminated Kuwaiti soil.

Rhamnolipids and nutrients boost remediation of crude oil-contaminated soil by enhancing bacterial colonization and metabolic activities

Bioaugmentation is a promising approach for the remediation of soil and water contaminated with petroleum hydrocarbons. Addition of rhamnolipids and nutrients in the soil enhance survival and metabolic activity of microbes and thus has the potential to restore the quality of soil to a greater extent. This study was carried out to evaluate the prospective role that these supplementary compounds can play in remediation of crude oil-contaminated soil by aiding bacterial strains to survive and perform better. A consortium of hydrocarbon degrading bacteria was inoculated in crude oil-contaminated soil and supplemented with different combinations of rhamnolipids and nutrients. Maximum crude oil-degradation of 77.6% was observed in the soil inoculated with hydrocarbon-degrading bacteria supplemented with rhamnolipids and nutrients. Moreover, addition of supplementary compounds enhanced bacterial survival as well as abundance and expression of alkane hydroxylase gene, alkB, in oil-contaminated soil. A strong positive relationship (r = 0.94) observed between gene expression and crude oil reduction indicates that catabolic gene expression is essential for hydrocarbon mineralization. All results from the investigation collectively confirm that addition of rhamnolipids and nutrients enhance bacterial colonization and metabolic activity thus improving remediation of crude oil-contaminated soil.