Hydrocarbon-contaminated Soil Research Articles

Environmental and economic performance of chemical and biological processes for treating petroleum hydrocarbon-contaminated soil: An experimental study

Over the past ten years, researchers have applied various approaches to treat petroleum hydrocarbon-contaminated soil and assess its performance based on removal efficiencies and not on its environmental and economic impacts. In this study, the environmental and economic performances of the operational stages of electro-Fenton and bio-slurry technologies are investigated and compared using a life cycle assessment to assess the environmental and economic performances in treating petroleum hydrocarbon-polluted soil. The data used in this study were collected from primary and secondary sources, and the potential 18 environmental impacts were calculated using the ReCiPe 2016 characterization approach in SimaPro 9.5 software. The electro-Fenton process is the most environmentally friendly method, identifying chemicals and energy as major contributors to the environmental impact. Energy is the main hotspot, accounting for 90 % of the total environmental impact. Energy and biosurfactants are the main environmental hotspots in bioslurry processes, accounting for 60 % of the total. The bioslurry process has the highest environmental impact owing to the use of biosurfactants and electricity consumption. The bioslurry process is the most cost-effective, with a life-cycle cost of 7.13$/kg, while the electro-Fenton technique is the most expensive (661.25$/kg) owing to the use of BDD as the electrode, costing 323$/kg.

Do phosphorus amendments enhance biodegradation activity in stalled petroleum hydrocarbon-contaminated soil?

Phosphorus (P) fertilizers promote soil petroleum-hydrocarbon (PHC) bioremediation by correcting carbon-to-P ratio imbalances. While these inputs create conditions favorable to microbial growth, areas of a site or an entire site with low degradation rates (i.e., "stalled") occur for unknown reasons. We hypothesized that soil conditions limit P bioavailability, leading to stalls in PHC bioremediation, and adding the correct P amendment restarts microbial activity. Soils were collected and characterized from four cold calcareous PHC-impacted sites in Saskatchewan, Canada, undergoing bioremediation. A generalized linear mixed model identified that regions with lower degradation rates possessed a neutral pH with high magnetic and salinity values. In a subsequent laboratory experiment, the proportion of benzene degraded at greater rates within active (i.e., higher degradation rates) than stalled soils, thereby following model predictions (p-value=0.19, Kruskal-Wallis). The PHC degradation efficiency of different P amendments was tested by doping stalled soils (n=3) with one of five treatments: 0 (control), 0 (autoclaved control), or 50mg phosphate kg-1 soil as sodium diphosphate, triethyl phosphate, or tripolyphosphate. Tripolyphosphate accelerated benzene degradation (75.5±5.4%) in one stalled soil (Outlook 323) and increased degradation non-significantly (43.9±9.4%) in another (Allan 917). Alternatively, the final sample (Davidson 421) possessed the greatest benzene removal with no amendments. This implies that soil P bioavailability may not be the sole cause of decreased microbial activity. Accordingly, combining model outputs with mineralogy and microbiology investigations could enhance PHC biodegradation rates in these cold calcareous soils.

Laboratory Evaluation of the Efficacy of Chlorine Dioxide (ClO2) Composite Powder for Remediation of Petroleum Hydrocarbon-Contaminated Soils

Laboratory Evaluation of the Efficacy of Chlorine Dioxide (ClO2) Composite Powder for Remediation of Petroleum Hydrocarbon-Contaminated Soils

Degradation of petroleum hydrocarbon contaminants by Rhodococcus erythropolis KB1 synergistic with alfalfa (Medicago sativa L.).

Petroleum hydrocarbons are a stubborn pollutant that is difficult to degrade globally, and plant-microbial degradation is the main way to solve this type of pollutant. In this study, the physiological and ecological responses of alfalfa to petroleum hydrocarbons in different concentrations of petroleum hydrocarbon-contaminated soil with KB1 (Rhodococcus erythropolis) were analyzed and determined by laboratory potting techniques. The growth of alfalfa (CK) and alfalfa with KB1 (JZ) in different concentrations of petroleum hydrocarbons contaminated soil was compared and analyzed. The results of the CK group showed that petroleum hydrocarbons could significantly affect the activity of alfalfa antioxidant enzyme system, inhibit the development of alfalfa roots and the normal growth of plants, especially in the high-concentration group. KB1 strain had the ability to produce IAA, form biofilm, fix nitrogen, produce betaine and ACC deaminase, and the addition of KB1 could improve the growth traits of alfalfa in the soil contaminated with different concentrations of petroleum hydrocarbons, the content of soluble sugars in roots, and the stress resistance and antioxidant enzyme activities of alfalfa. In addition, the degradation kinetics of the strain showed that the degradation rate of petroleum could reach 75.2% after soaking with KB1. Furthermore, KB1 can efficiently degrade petroleum hydrocarbons in advance and significantly alleviate the damage of high concentration of petroleum hydrocarbons to plant roots. The results showed that KB1 strains and alfalfa plants could effectively enhance the degradation of petroleum hydrocarbons, which provided new ideas for improving bioremediation strategies.

Remediation of petroleum hydrocarbon contaminated soils by nZVI coupled with electrokinetic activation of persulfate

This paper explores the use of nanoscale zero-valent iron (nZVI) coupled with electrically activated persulfate (nZVI-EK/PS) for remediating petroleum hydrocarbon-contaminated soil. The effects of persulfate (PS) dosage, nZVI dosage, and soil organic matter content on the remediation of petroleum hydrocarbons were investigated. The study concludes that persulfate (PS) and nanoscale zero-valent iron (nZVI) are the primary factors influencing the remediation of petroleum hydrocarbons in the nZVI-EK/PS system. The optimal reaction conditions of PS = 170 mmol and nZVI = 17 mmol increased the efficiency of petroleum hydrocarbon treatment to 40.45%, with the highest removal efficiency of petroleum hydrocarbons observed at position S2, reaching 48.5%. With the addition of organic matter at 5%, the efficiency of petroleum hydrocarbon treatment reached 50.08%, representing a 9.68% enhancement in the nZVI-EK/PS system. Furthermore, potential mechanisms for the degradation of petroleum hydrocarbons by the nZVI-EK/PS system were identified using gas chromatography-mass spectrometry (GC-MS). The degradation order of different components was found to be esters < alkenes < alkanes < phenols.

Remediation of Polycyclic Aromatic Hydrocarbon-Contaminated Soil by Using Activated Persulfate with Carbonylated Activated Carbon Supported Nanoscale Zero-Valent Iron

Soil contamination by polycyclic aromatic hydrocarbons (PAHs) has been an environmental issue worldwide, which aggravates the ecological risks faced by animals, plants, and humans. In this work, the composites of nanoscale zero-valent iron supported on carbonylated activated carbon (nZVI-CAC) were prepared and applied to activate persulfate (PS) for the degradation of PAHs in contaminated soil. The prepared nZVI-CAC catalyst was characterized by scanning electron microscopy (SEM), X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). It was found that the PS/nZVI-CAC system was superior for phenanthrene (PHE) oxidation than other processes using different oxidants (PS/nZVI-CAC &gt; PMS/nZVI-CAC &gt; H2O2/nZVI-CAC) and it was also efficient for the degradation of other six PAHs with different structures and molar weights. Under optimal conditions, the lowest and highest degradation efficiencies for the selected PAHs were 60.8% and 90.7%, respectively. Active SO4−• and HO• were found to be generated on the surface of the catalysts, and SO4−• was dominant for PHE oxidation through quenching experiments. The results demonstrated that the heterogeneous process using activated PS with nZVI-CAC was effective for PAH degradation, which could provide a theoretical basis for the remediation of PAH-polluted soil.

Enhancement of oil biodegradation by using the biosurfactant produced from local Bacillus subtilis isolate

Background: Oil contamination poses a significant threat to the global environment and has attracted widespread attention in recent years. Given its significance, further exploration of biodegradation options for this contamination has never been more crucial than it is today. Therefore, the objective of the study was to improve the biodegradation of oil by utilizing local bacterial isolates alongside a biosurfactant produced by a Bacillus subtilis isolate. Twenty-two bacterial isolates were collected from four samples of hydrocarbon-contaminated soil. These isolates underwent screening to assess their effectiveness in degrading crude oil using two distinct methods.Methods: Soli samples were collected from two contaminated sites with oil pollutants in Baghdad city. Biodegradation ability was tested on liquid Bushnell Haas medium (BH), pH 7 supplemented with 1% of crude oil and then screened primarily using the 2,6-dichlorophenol indophenol method to determine the ability of isolates to degrade the crude oil. All isolates were identified morphologically and biochemically. Biosurfactants was extracted from Bacillus subtilis previously isolated.Results: Isolate SCS1 has appeared the highest ability reaching 52.6% compared with other isolates, also, the results of secondary screening confirmed that isolate SCS1 has given the best biodegradation reaching 53.8%. The isolate SCS1 was identified as Pseudomonas aeruginosa, this isolate was used to study the effect of biosurfactant on crude oil biodegradation. Results exhibited a high biodegradation efficiency reaching 85.1% in culture broths supplemented with 100 mg/100. It was noted that the use of 150 and 200 mg of biosurfactant led to a decrease in the biodegradation of crude oil.Conclusion: The use of biosurfactant led to an increase in the degradation rate by up to 61.7% of crude oil by Pseudomonas aeruginosa when using 25-100 mg of crude biosurfactant that produced by local isolate Bacillus subtilis.Keywords: Biodegradation; Biosurfactant; Bacillus subtilis; Pseudomonas aeruginosa

Investigating the influence of sulphur amendment and temperature on microbial activity in bioremediation of diesel-contaminated soil

This study investigated the effectiveness of incorporating sulphur (S) with nitrogen (N) and phosphorus (P) for enhancing microbial activity in diesel-contaminated soil during ex-situ bioremediation. While N and P amendments are commonly used to stimulate indigenous microorganisms, the potential benefits of adding S have received less attention. The study found that historically contaminated soil with a moderate concentration of total petroleum hydrocarbons (TPH; 1270 mg/kg) did not have nutrient limitation, and incubation temperature was found to be more critical for enhancing microbial activity. However, soil spiked with an additional 5000 mg/kg of diesel showed increased activity following NP and NPS amendment. Interestingly, NPS amendment at 10 °C resulted in higher microbial activity than at 20 °C, indicating the potential for a tailored nutrient amendment approach to optimize bioremediation in cold conditions. Overall, this study suggests that incorporating S with N and P can enhance microbial activity in diesel-contaminated soil during ex-situ bioremediation. Furthermore, the study highlights the importance of considering incubation temperature in designing a nutrient amendment approach for bioremediation, especially in cold conditions. These findings can guide the design and implementation of future effective bioremediation strategies for petroleum hydrocarbon-contaminated soil.

New Silicon-Rich Mineral-Based Materials and Their Use for Remediation of Hydrocarbon-Contaminated Soil

New Silicon-Rich Mineral-Based Materials and Their Use for Remediation of Hydrocarbon-Contaminated Soil

Evaluation of lipopeptides biosurfactant from Raoultella planticola for bioremediation in n-hexadecane-contaminated soil

Biosurfactants combined with bioaugmentation for the remediation of petroleum hydrocarbon-contaminated soils proved to be one of the most effective ways. However, research on lipopeptides combined with bioaugmentation is rare, and the biological mechanisms are undefined. Therefore, the effect of Raoultella planticola and the lipopeptides it produces to restore contaminated soils was investigated using n-hexadecane as a model of petroleum hydrocarbons. After 60 d, n-hexadecane removal rate increased from 31.3% in contaminated soil to 39.9% with R. planticola alone and 59.0% with R. planticola together with 1.0 g intracellular lipopeptide (INLS) and 7.5 g sodium gluconate (SG)/kg dry soil. Meanwhile, the nitrogen and phosphorus components of the soil increased by 13.9% and 8% in the experimental group, respectively. Besides, DHA activity was 6.7 times that of the control group at 28 d, indicating a considerable increase in DHA activity. Microbial community analysis revealed a considerable increase in functional genera of Sphingomonas, Nocardia, Pseudoalteromonas, Povalibacter, Apiotrichum, Pseudallecheria, and Ascodesmis. The amount of fungus in the experimental group was more than 30 times that of the control group after 60 d. Microbial co-occurrence networks showed improved interactions of Firmicutes and Ascomycota, encouraging synergistic cooperation among microbes and thereby accelerating n-hexadecane breakdown. At once, the metabolic pathways ko00071 and ko00980 for n-hexadecane degradation were greatly elevated, indicating that functional genes such as alkane 1-monooxygenase and NADPH-cytochrome P450 reductase were activated. These results implied that combining hydrocarbon-degrading microbial with INLS was a promising bioremediation technique to remove soil petroleum hydrocarbons.

Biodegradation of a complex hydrocarbon mixture and biosurfactant production by Burkholderia thailandensis E264 and an adapted microbial consortium.

Bioremediation is considered to be an effective treatment for hydrocarbon removal from polluted soils. However, the effectiveness of this treatment is often limited by the low availability of targeted contaminants. Biosurfactants produced by some microorganisms can increase organic compound solubility and might then overcome this limitation. Two different inocula producers of biosurfactants (Burkholderia thailandensis E264 and SHEMS1 microbial consortium isolated from a hydrocarbon-contaminated soil) were incubated in Bushnell-Haas medium supplemented with hydrocarbons to investigate their biodegradation potential. Experimental results showed their ability to degrade 9.1 and 6.1% of hydrocarbons respectively after 65 days of incubation with an initial total hydrocarbon concentration of 16 g L-1. The biodegradation was more effective for the light and medium fractions (C10 to C36). B. thailandensis and SHEMS1 consortium produced surfactants after 14 days of culture during the stationary phase with hydrocarbons as the sole carbon and energy source. However, biosurfactant production did not appear to directly increase hydrocarbon degradation efficiency. The complexity and recalcitrance of hydrocarbon mixture used in this study appeared to continue to limit its biodegradation even in the presence of biosurfactants. In conclusion, B. thailandensis and SHEMS1 consortium can degrade recalcitrant hydrocarbon compounds and are therefore good candidates for the bioremediation of environments polluted by total hydrocarbons.

Effect of the Application of Ochrobactrum sp.-Immobilised Biochar on the Remediation of Diesel-Contaminated Soil.

The immobilisation of bacteria on biochar has shown potential for enhanced remediation of petroleum hydrocarbon-contaminated soil. However, there is a lack of knowledge regarding the effect of bacterial immobilisation on biosolids-derived biochar for the remediation of diesel-contaminated soil. This current study aimed to assess the impact of the immobilisation of an autochthonous hydrocarbonoclastic bacteria, Ochrobacterium sp. (BIB) on biosolids-derived biochar for the remediation of diesel-contaminated soil. Additionally, the effect of fertiliser application on the efficacy of the BIB treatment was investigated. Biochar (BC) application alone led to significantly higher hydrocarbon removal than the control treatment at all sampling times (4887-11,589 mg/kg higher). When Ochrobacterium sp. was immobilised on biochar (BIB), the hydrocarbon removal was greater than BC by 5533 mg/kg and 1607 mg/kg at weeks 10 and 22, respectively. However, when BIB was co-applied with fertiliser (BIBF), hydrocarbon removal was lower than BIB alone by 6987-11,767 mg/kg. Quantitative PCR (q-PCR) analysis revealed that the gene related to Ochrobacterium sp. was higher in BIB than in the BC treatment, which likely contributed to higher hydrocarbon removal in the BIB treatment. The results of the q-PCR analysis for the presence of alkB genes and FTIR analysis suggest that the degradation of alkane contributed to hydrocarbon removal. The findings of this study demonstrate that bacterial immobilisation on biosolids-derived biochar is a promising technique for the remediation of diesel-contaminated soil. Future studies should focus on optimising the immobilisation process for enhanced hydrocarbon removal.

Research Progress on in-situ Remediation of Typical Heavy Metals in Petroleum Hydrocarbon-contaminated Soil Enrichment by Plants

Petroleum hydrocarbon is one of the dangerous substances in the process of petroleum development, refining, processing, transportation, and production. In the related activities of the petroleum industry, the output is large, and improper treatment will cause pollution to the surrounding environment. It is an urgent problem to conduct harmless and resource treatment of petroleum hydrocarbon polluted soil. Plant enrichment, as an environmentally friendly and pollution-free technical means, has the advantages of low cost and small change to the soil environment and effectively solves the problems of excessive heavy metals in petroleum hydrocarbons through plant enrichment. In this paper, the development process of plant enrichment, remediation methods, and plant enrichment of typical heavy metals (Cd, Hg, Zn) in petroleum hydrocarbon-polluted soil were systematically introduced. Through investigation, the mechanism and influencing factors of plant enrichment of heavy metals in the presence of petroleum hydrocarbons were summarized and analyzed, and the possible development direction of plant enrichment technology in the future was prospected.

Biodegradation of petroleum hydrocarbons using a novel bacterial strain isolated from hydrocarbons contaminated soil of Saudi Arabia

Petroleum spills pose a significant environmental threat, underscoring the need for efficient pollution removal methods. Bioremediation, employing bacterial cultures, emerges as a cost-effective and eco-friendly technique. The success of this method hinges on whether petroleum pollution is eliminated or converted into a harmless form. This study seeks to isolate a bacterial strain exhibiting excellent capacity for degrading petroleum hydrocarbons. Biochemical tests and 16S rRNA results identified various Microbacterium spp., namely Microbacterium barkeri (SA9) and Microbacterium deserti (SA2, SA3, SA5, and SA7), isolated from hydrocarbon-contaminated soil. Within five days, these strains demonstrated degradation percentages of 20.91%, 38.51%, 77.68%, 22.51%, and 31.11% for petroleum, respectively. Phylogenetic and sequence analyses targeting the 16S rRNA gene revealed that M. barkeri (accession number ON 421582) is closely related to strains from India and Saudi Arabia, while M. deserti (ON 421525, ON 421524, ON 421523, and ON 421522) shares affinity with strains from Saudi Arabia, China, and India. Furthermore, these isolates produced a stable emulsion with E−24% of 25% for 72 h. Notably, this marks the first study exploring the use of these bacterial strains for petroleum bioremediation in Saudi Arabia.

ENHANCEMENT OF DECONTAMINATION OF PETROLEUM HYDROCARBONS IN CRUDE OIL POLLUTED SOIL BY USING CYCLODEXTRINS

Soil contaminated by total petroleum hydrocarbons is a well-recognized worldwide problem because of its strong persistence in the environment and its potentially toxic effects on human beings, animals and microorganisms. During the past three decades, the research and development of remediation technology for petroleum hydrocarbons-contaminated soil have been systematically studied such as the physical, chemical and bioremediation technologies. To address the associated environmental concerns, innovative remediation technologies are urgently needed. Cyclodextrins are nonhazardous and environmentally acceptable organic substances that have been shown to be biodegradable in soil and water after their introduction into an environmental system. The decontamination technique based in cyclodextrin extraction has been developed to eliminate petroleum hydrocarbons. Cyclodextrins have successfully been used in soil cleaning technologies as solubiliser–carrier molecules. These molecules can transfer continuously the insoluble contaminants from the soil surface to the aqueous phase by complex formation. In the aqueous phase the microorganisms can degrade the contaminants much easier partly because these molecules become available for the microbial cells, partly because the entrapment of contaminants by cyclodextrins reduces their toxicity.

Relationships among protozoa, bacteria and fungi in polycyclic aromatic hydrocarbon-contaminated soils

Soil bacterial and fungal communities play key roles in the degradation of organic contaminants, and their structure and function are regulated by bottom-up and top-down factors. Microbial ecological effects of polycyclic aromatic hydrocarbons (PAHs) and trophic interactions among protozoa and bacteria/fungi in PAH-polluted soils have yet to be determined. We investigated the trophic interactions and structure of the microbiome in PAH-contaminated wasteland and farmland soils. The results indicated that the total concentration of the 16 PAHs (∑PAHs) was significantly correlated with the Shannon index, NMDS1 and the relative abundances of bacteria, fungi and protozoa (e.g., Pseudofungi) in the microbiome. Structural equation modelling and linear fitting demonstrated cascading relationships among PAHs, protozoan and bacterial/fungal communities in terms of abundance and diversity. Notably, individual PAHs were significantly correlated with microbe-grazing protozoa at the genus level, and the abundances of these organisms were significantly correlated with those of PAH-degrading bacteria and fungi. Bipartite networks and linear fitting indicated that protozoa indirectly modulate PAH degradation by regulating PAH-degrading bacterial and fungal communities. Therefore, protozoa might be involved in regulating the microbial degradation of PAHs by predation in contaminated soil.

Performance evaluation of electrokinetic bioremediation for weathered petroleum hydrocarbon-contaminated soil

This study investigates the impact of Electrokinetic Remediation (EKR) time on total petroleum hydrocarbons (TPH) removal from soil, focusing on electroosmotic phenomena guided by Helmholtz-Smoluchowski theory. Soil samples were exposed to a constant 2 V/cm voltage gradient for 8, 16, and 24 hours, utilizing a 0.05 M Na2SO4 solution as an electrolyte to enhance soil conductivity. Biostimulation was combined with EKR, and TPH levels and microbial colonies (TPC) were monitored over a 4-week period. Maintaining optimal conditions (25-40°C, pH 6-8, 30-60% water content) was crucial for effective biodegradation. Results showed that a 24-hour EKR duration was most effective, achieving an 87.9% removal rate. The 16-hour duration closely followed at 85.7%, while the 8-hour duration exhibited lower effectiveness at 62.5%. TPC counts increased in the fourth week for the 16-hour and 24-hour durations but decreased for the 8-hour duration. Post-EKR, a gradual decline in TPH levels indicated electroosmotic flow’s (EOF) positive impact on TPH desorption and biodegradation. Electroosmosis influence was evident in varying TPH concentrations among segments after EKR, with higher levels near the cathode in the 16-hour and 24-hour durations. Lower TPH near the cathode in the 8-hour variation suggested electroosmosis-induced desorption, while reduced concentrations in regions A (near anode) and B (middle) resulted from biodegradation and microbial mobility due to electrophoresis. Confirmation of electroosmosis across all durations was supported by observed water content and EOF volume. The 24-hour duration exhibited the highest EOF proportion in the cathode chamber at 22.2%, followed by 16 hours at 16.1%, and 8 hours at 8.6%.

Primary Mathematical Modeling of the Growth of Diesel by a Bacterium Isolated from a Hydrocarbon-contaminated Soil

Mathematical modeling of microbial growth via nonlinear regression is essential for determining key parameters such as the maximum specific growth rate, which are foundational for secondary modeling. Models such as modified Gompertz, modified Logistic, modified Richards, Buchanan-3-phase, Baranyi-Roberts, modified Schnute, von Bertalanffy, Morgan-Mercer-Flodin (MMF), and Huang elucidate the impact of substrates on bacterial growth and biotransformation processes, vital for biotechnological applications like wastewater treatment and bioremediation. A previously isolated diesel-degrading Pseudomonas sp. strain Neni-4 growth on diesel was modeled using the aforementioned primary models. Experimental data showed that diesel concentrations from 0.25 to 3.5% (v/v) are toxic, slowing bacterial growth and increasing lag periods from 3 to 15 hours. Among the primary models tested, the Baranyi-Roberts model provided the best fit, evidenced by a high adjusted coefficient of determination, low RMSE and AICc values, and favorable accuracy (AF) and bias factors (BF). The reliability of the Baranyi-Roberts model underscores its suitability for modeling bacterial growth under toxic conditions, offering valuable insights for optimizing biotechnological processes involving bacterial adaptation and growth under stress conditions.

Application of Organic Amendment from Kitchen Waste Composting for Enhanced Bioremediation of Petroleum Hydrocarbon-Contaminated Soil

Application of Organic Amendment from Kitchen Waste Composting for Enhanced Bioremediation of Petroleum Hydrocarbon-Contaminated Soil

Slow-release microencapsulates containing nanoliposomes for bioremediation of soil hydrocarbons contaminated

ABSTRACT Encapsulation and nutrient addition in bacterial formulations have disadvantages concerning cell viability during release, storage, and under field conditions. Then, the objective of this work was to encapsulate a bacterial consortium with hydrocarbon-degrading capacities in different matrices composed of cross-linked alginate/ polyvinyl alcohol /halloysite beads (M1, M2, and M3) containing nanoliposomes loaded with or without nutrients and evaluate their viability and release in a liquid medium, and soil (microcosmos). Also, evaluate their capacity to remove total petroleum hydrocarbons (TPH) for 165 days and matrices characterization. The encapsulate consortium showed a quick adaptation to contaminated soil and a percentage of removal (PR) of TPH up to 30% after seven days. All the matrices displayed a PR of up to 90% after 165 days. The matrix M2 displayed significant resistance to degradation and higher cell viability with a PR of 94%. This result supports the encapsulation of bacteria in a sustainable matrix supplemented with nutrients as a well-looked strategy for improving viability and survival and, therefore, enhancing their effectiveness in the remediation of hydrocarbon-contaminated soils.