Cost reduction strategies in the remediation of petroleum hydrocarbon contaminated soil.

Petroleum hydrocarbon spill on land pollutes soil and reduces its ecosystem. Hydrocarbon transport in the soil is aided by several biological, physical, and chemical processes. However, pore characteristics play a major role in the distribution within the soil matrix. Restoring land use after spills necessitates remediation using cost-effective technologies. Several remediation technologies have been demonstrated at different scales, and research is ongoing to improve their performances towards the reduction of treatment costs. The process of removing the contaminants in the soil is through one or a combination of containment, separation, and degradation methods under the influence of biological, physical, chemical, and electrically-dominated processes. Generally, performance improvement is achieved through the introduction of products/materials and/or energy. Nevertheless, the technologies can be categorized based on effectiveness period as short, medium, and long term. The treatment cost of short, medium, and long-term technologies are usually in the range of $39 - 331/t (/tonne), $22 - 131/t, and $8 - 131/t, respectively. However, the total cost depends on other factors such as site location, capital cost, and permitting. This review compiles cost-saving strategies reported for different techniques used in remediating petroleum hydrocarbon polluted soil. We discuss the principles of contaminant removal, performance enhancing methods, and the cost-effectiveness analysis of selected technologies.

Selenium abates manganese-induced striatal and hippocampal toxicity via abrogation of neurobehavioral deficits, biometal accumulation, oxidative stress, inflammation, and caspase-3 activation in rats.

Excessive exposure to manganese (Mn) is associated with neurotoxicity characterized by oxidative stress, inflammation, and apoptosis induction. Selenium (Se) has been shown to possess antioxidant, anti-inflammatory, and anti-apoptotic properties in humans and animals. The present study investigated the neuroprotective mechanism of Se in rats sub-chronically treated with Mn at 30 mg/kg body weight or orally co-treated with Se at 0.2 and 0.4 mg/kg body weight for 35 consecutive days. Locomotive and exploratory profiles were recorded and computed with the aid of ANY-Maze (a video-tracking software) for 5-min trial, in a novel apparatus. The ANY-Maze analysis showed that Se significantly (p < 0.05) abated Mn-induced locomotive impairment evidenced by increased in maximum speed, total time traveled, absolute turn angle, number of line crossing, rotation and forelimb grip and decreased total time immobile, grooming, and negative geotaxis as verified by the enhanced track plot density. Furthermore, the striatum and hippocampus of the rats were excised and the levels of Mn and Se, oxidative stress markers, proinflammatory cytokines including acetylcholinesterase and caspase-3 activities were assayed. The result shows that Se abates Mn-mediated accumulation of Mn. Also, Se ameliorated Mn-induced decrease in antioxidant enzymes as well as glutathione level and increase in acetylcholinesterase activity, lipid peroxidation, proinflammatory cytokines (i.e., interleukin (IL)-6, IL-1ß, tumor necrosis factor alpha), and caspase-3 activation in the striatum and hippocampus of the rats. Collectively, Se abated Mn-induced striatal and hippocampal toxicity via abrogation of neurobehavioral deficits, biometal accumulation, oxidative stress, inflammation, and caspase-3 activation in rats. Se may serve as a neuroprotective agent against Mn-mediated neurotoxicity.

Attenuation of petroleum hydrocarbon fractions using rhizobacterial isolates possessing alkB, C23O, and nahR genes for degradation of n-alkane and aromatics.

This work assessed the catabolic versatility of functional genes in hydrocarbon-utilizing bacteria obtained from the rhizosphere of plants harvested in aged polluted soil sites in Ogoni and their attenuation efficacy in a bioremediation study. Rhizosphere soil was enumerated for its hydrocarbon-utilizing bacteria. The bacteria were in-vitro screened and selected through the quantification of their total protein and specific intermediate pathway enzyme (catechol 2,3-dioxygenase) activity in the metabolism of hydrocarbon. Thereafter, agarose gel electrophoresis technique was deployed to profile the genome of the selected strains for catechol 2,3-dioxygenase (C23O), 1,2-alkane monooxygenase (alkB), and naphthalene dioxygenase (nahR). Four rhizobacterial isolates namely Pseudomonas fluorescens (A3), Achromobacter agilis (A4), Bacillus thuringiensis (D2), and Staphylococcus lentus (L1) were selected based on the presence of C23O, alkB, and nahR genes. The gel electrophoresis results showed an approximate molecular weight of 200 bp for alkB, 300 bp for C23O, and 400 bp for nahR. The gas chromatogram for residual total petroleum hydrocarbon (TPH) revealed mineralization of fractions C8-C17, phytane, C18-C30. TPH for in-vitro bioremediation of crude oil-polluted soil was observed to have an optimal reduction/loss of 97% within the 56th day of the investigation. This study has further revealed that the microbiome of plants pre-exposed to crude oil pollution could serve as a reservoir for mining group of bacterial with broad catabolic potentials for eco-recovery and waste treatment purposes.

Optimization of bioremediation-cocktail for application in the eco-recovery of crude oil polluted soil.

Background: Environmental sustainability is the driver for finding the optimal bioremediation cocktail with the combination of highly potent hydrocarbonoclastic strains and the nutrient additives that significantly enhance mineralization of crude oil in polluted soil in order to mitigate its deleterious effects on the environment. In this study, four hydrocarbon-degrading bacterial strains were pre-selected from mined rhizobacterial isolates in aged crude oil-contaminated soil.  Method: Agrowaste residues of poultry-droppings, corn chaff, and plantain peel were selected among others for their ability to support high biomass of selected bacterial strains. Baseline proximate analysis was performed on the agrowaste residues. Simplified, one variable at a time (OVAT) was employed in the validation of the variables for optimization using the Multivariate analysis tool of Response Surface Methodology (RSM). To test the significant formulation variables, the Box-Behnken approach using 15 runs design was adopted. Results:  The rate of contaminant removal was observed to fit into a quadratic function. For optimal rate or contaminant removal, the fitted model predicted the optimal formulation cocktail condition to be within 0.54 mg/kg (Corn steep liquor), phosphate 137.49 mg/kg (poultry droppings) and 6.4% inocula for initial TPH of 9744 mg kg -1 and THC of 9641 mg kg -1 contaminant level. The model for the application of the bioremediation product and the variables evaluated had a significant p-value < 0.005 for the attainment of 85 to 96 % of TPH and THC removal after 56 days of treatment. Conclusions:  This study has shown the need to harness the abundant agrowaste nutrients in supporting high throughput rhizobacteria in the formulation of a bioremediation agent suitable for use in the reclamation of oil spill sites in the Niger Delta oil-producing region.

Evaluation and decontamination of crude oil-polluted soils using Centrosema pubescen Benth and amendment-support options.

Growth performance and phytoremediation of soil of the Niger Delta Region of Nigeria artificially-contaminated with crude oil (up to 100 mL/2 kg soil) using centrosema pubescen Benth was investigated for 12 weeks. The soil samples in which the plants were established were either un-amended, or amended with NPK, or UREA or chicken manure. The extents of removal of PAHs and BTEX were measured as well as the rates of growth of the plants. Gas Chromatographic analysis confirmed the degradation of carcinogenic hydrocarbons like BTEXs and PAHs with this technique. At the highest dose of crude, the contaminant concentrations were 43 mg/kg PAHs, 10 mg/kg BTEX, and 5,613 mg/kg O&G. The greatest percent removal of BTEX was observed at the highest contaminant dose, and with the manure amendment. Similar trends were observed with PAHs and although they were less marked, the trends with PAHs may have been more highly statistically significant. There was no measurable plant uptake of contaminants. Inhibition of plant growth (measured as leaf area, shoot length and production of dry weight) was proportional to the dose of crude oil, but the manure amendment was very effective at reducing the growth inhibition. Interestingly, manure amendment reduced the phytotoxicity significantly in this study.

Characterization and safety evaluation of the impact of hydrocarbon contaminants on ecological receptors.

Hydrocarbon-contaminant removal efficiency of Bambara groundnuts and biomagnification was investigated. The crude oil contaminated soil samples in which the plants were established were either un-amended, or amended with NPK, or Urea, or Poultry manure. Amendments improved phytoextraction rates as follows: Urea - 63.37%, NPK - 65.99%, Poultry - manure - 70.04%, for PAH; Urea - 78.80%, NPK - 79.80%, Poultry manure - 87.90%, for BTEX. Hazard characterization from 28-day feeding study revealed negative effects of potentially toxic BTEX and PAH on organ weight, optimum digestibility and animal growth rate. Sleep time decreased with increasing hydrocarbon concentrations probably due to increased liver enzyme activity.