Rapid Bioremediation of Refinery Sludge with BioRemove HC

Background

A crude oil refinery in Central America needed to remove 7,300 yd³ (5,580 m³) of oily sludge that had collected in waste reservoirs over an 8-year period. The sludge had an extractable petroleum hydrocarbon (EPH) concentration of 79,000 mg/kg that consisted primarily of C₁₄ to C₄₀ hydrocarbons. A US engineering firm acted as lead consultant for the project and investigated bioremediation strategies with EnviroZyme as an alternative to disposal in an environmental landfill or incineration.

Solution

The goal for the project was to reduce the average EPH concentration below 10,000 mg/kg as quickly as possible. Since long-chain hydrocarbons are difficult and often slow to degrade, it was felt that bioaugmentation was necessary to ensure that a capable population of bacteria existed in the soil. EnviroZyme recommended BioRemove HC, a blend of selectively adapted bacterial cultures that is particularly effective at degrading diesel range organics with additional effectiveness in degrading longer-chain aliphatic hydrocarbons.

BioRemove HC

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BioRemove HC

BioRemove HC is the most effective biological solution for degrading hydrocarbons like alkanes, phenols, and aromatic compounds such as benzene, toluene, ethylbenzene, and xylene (BTEX). BioRemove HC contains a combination of microorganisms that are specially blended for petroleum refining and petrochemical applications. BioRemove HC is also tolerant and effective in high-salinity wastewaters, which makes it a very versatile product.

• Improves effluent quality and plant stability through enhanced hydrocarbon degradation
• Lower operating costs by reducing permit violations for oil and grease
• Reduces hydrocarbon-related filament outbreaks and settling problems
• Simplify operations by improving system stability

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2 land treatment cells (LTCs), 1 to 2 acres (0.4 - 0.8 ha) in size, were constructed adjacent to the waste reservoirs. The petroleum sludge was dredged, mixed with soil, lime, and Portland cement for bulking and stabilization, and then spread in the LTCs for biological treatment. The mixture was graded, tilled, and treated with nitrogen- and phosphorous-based fertilizers prior to the application of 3,500 pounds (1,580 kg) of dry BioRemove HC. The product was rehydrated with water immediately and thoroughly tilled into the soil. After the initial inoculation, the soil was tilled at least weekly to provide mixing and oxygen for the bacteria.

Results

The baseline EPH concentration of the sludge/soil mixture averaged 29,195 mg/kg at the time BioRemove HC was applied. At the 90-day sample date, the average EPH concentration had already decreased to 9,395 mg/kg. Out of 20 samples analyzed, only 3 “hot spots” that had been water-saturated during much of the 90-day period were still above the 10,000-mg/kg limit. The project was closed following a brief period of concentrated tilling to oxygenate the soil in these areas.