Utilization of Combined Technologies to Recover Hydrocarbons and Treat Residual Sediments

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This article describes the utilization of combined technologies aimed to recover hydrocarbon and treat the residual sediments in a relatively very short time. In this project, oily sludge which was stored inside a lined pit was treated using a combination of centrifugation, bio-cells and bioreactor technologies. The project was implemented by Industrial Supply center (ISC), branch of Environmental Technology. The First phase of the project involved the removal of liquid, recovery of oil using centrifugation, and the transfer of the clean oil to a newly constructed pit. The second phase included the bioremediation, treatment of residual soil and sludge using engineered biopile and bioreactor technologies.

Risk assessment study was conducted to find the most cost effective and environmentally responsible way to manage oily pits. The following provides a summary of the oil recovery and bioremediaum degrading microorganisms present in soil and sludge obtained from the pit. No microbial culture was either imported or brought in from any other parts outside the country.

Total 14 treatment Biocells (15 m L x 5 m W x 2.5 m H) and one control Biocell equipped with air, water and nutrient supply provisions were prepared for the treatment of contaminated soil/ sand. During Biocell treatment process of contaminated sand, they were covered using tarps to retain moisture and evaporation of any volatile hydrocarbon to mitigate any air pollution. For sampling, a composite sample was prepared by mixing 8 samples from different location in each biocell and was analyzed for hydrocarbons and other parameters in a certified laboratory.

The soil treatment time varied from 6 weeks to 12 weeks in An Oily sludge pit before and after treatment and pit closure tion methodology of the project.

Around 50,000 bbl of liquid was removed from the pit, oil recovery was achieved using a three-phase centrifuge unit with a production capacity of 10 m3 per hour for separation of oil and solids. Approximately 47,000 bbl (>7,700 m3) of oil was recovered and transferred to a storage pond.

Approximately 3000 m3 of contaminated soil was removed for treatment with engineered biopile technology. Enhanced bioremediation or biological processes are cost effective methods for treatment of petroleum contaminated soil and oily sludge because there is no extreme temperature / pressure involved, controlled process with predictable results, robust to sludge variation, conversion of hazardous wastes to non-hazardous residues and no toxic byproducts generation. The microbial culture / inoculum for the Biocells was developed on site in a 50 m3 capacity Bioreactor using a blend of nutrients designed by ISC Canada for accelerated growth of indigenous or naturally occurring microbial population petroledifferent Biocells. During treatment, significant reduction in hydrocarbons in all the Biocells was achieved and the treated soil met the US EPA non-hazardous criteria and limits for TCLP – volatiles and semi-volatiles and further confirmed by bulk analysis of the BTEX and PAHs. Based on the final analysis results, completion of the treatment of the Biocells was established. After econtamination of the pit and treatment of contaminated soil, the treated soil was backfilled in the pit to close and level the surface.

A carefully designed blend of nutrients was used for proper microbial growth and maintenance of the culture during our bioreactor process. In the presence of appropriate nutrients, high growth rate of microorganisms is promoted, hydrocarbon bioavailability increased, and desorption of contaminants also improved, resulting in enhanced degradation of toxic mobile hydrocarbon compounds.

A batch of oily sludge was treated in bioreactor for the demonstration purpose using a nutrient mixture developed by the ICS Canada for optimum microbial growth and activity. The bioreactor was operated for 15 days and A rapid reduction in TPH content from 10% at day 1 to 0.5% on day 13 achieving 95% degradation of hydrocarbons. The bioreactor contents were later used for completion of the treatment of control Biocell. If we compare this method to land farming, which takes approximately 1 year to achieve the same results, the advantages and benefits can be clearly realized. The treatment of the oily sludge pit was treated successfully. An integrated approach of oil recovery and enhanced bioremediation was demonstrated using centrifuge, bioreactor and biopile technologies.

Raed Al-Atrash is a Projects Manager with Industrial Supplies Company (ISC) based in Al-Khobar, Saudi Arabia.

 

The Asia Environmental Daily