The results of a recent bench-scale test confirmed the effectiveness of a special blend of CL Solutions’ microbes formulated for PAH bioremediation. The test results showed that after two weeks, the total concentration of 15 PAH compounds decreased by 85% from a total of 358 mg/kg to 50.9 mg/kg. Benzo(A)pyrene is often a most difficult PAH to remove. The test showed that the custom blend reduced the benzo(A)pyrene concentration from 24.5 mg/kg to 3.68 mg/kg. Tests will continue to determine whether even greater effectiveness can be achieved over 30 days.
Recent data from field applications of Petrox bioremediation show degradation rates of 100 to 500 micrograms per liter (ug/ml) per day. These degradation rates are for total petroleum hydrocarbons or total BTEX, depending on the site monitoring requirements.
Achieving high degradation rates requires high initial concentrations. Initial concentrations of 1,000 to 10,000 ug/l were used to develop these degradation rates.
At lower concentrations, the degradation rates depend on effective distribution of microbes for cell to contaminant contact. Secondly, desorption of petroleum constituents from submerged soil may cause rebound and suggest lower degradation rates. For these reasons we cannot calculate a degradation rate for petroleum at low concentrations.
Petrox microbes were added to excavated petroleum-contaminated soil to accelerate the degradation of DRO and ERO total petroleum hydrocarbons. Petrox was added by spraying the surface of the soil with a hydrated Petrox solution. The microbes were mixed into the soil using a tractor-mounted disc tiller.
After approximately 60 days, soil samples were taken for testing. The soils showed 90% to 99% petroleum removal. The following chart shows the range of DRO and ERO concentrations before and after Petrox treatment.
Petrox bioremediation accelerates the removal of naphthalene and isomers of methylnaphthalene. These petroleum compounds are often slow to remediate due to their low volatility and strong affinity for absorption onto soil particles. The remediation rate of these compounds is slower than BTEX compounds. They often also rebound as the absorbed phase solubilizes following removal of the compound from ground water to reestablish phase equilibrium. Petrox bioremediation accelerates the remediation of these compounds by a combination of metabolizing the dissolved phase and a biosurfactant effect that strips the compound from soil to make it available for metabolism.
For example, Petrox achieved more than 90% removal of these compound in less than 9 months at a site of a former underground storage tank (UST) in Florida. After the UST and surrounding contaminated soil were removed, the residual BTEX compounds were treated by chemical oxidation. The chemical oxidation, however, did not remove the naphthalene and methylnaphthalene isomers. Petrox was applied to the ground water in and around the former UST cavity.
Nine months after the Petrox application the following reductions in concentrations were achieved. The concentrations are the average of four ground water sampling locations.
Naphthalene – 367 ug/L reduced to 18 ug/L, 95% removal.
1 Methylnaphthalene – 255 ug/L reduced to 33 ug/L, 87% removal.
2 Methylnaphthalene – 400 ug/L reduced to 30 ug/L, 93% removal.
The Petrox was injected into the ground through a continuous low-volume injection system. This application method did not impact the use of the property or require major construction. The application was also far less costly than alternatives.
The greatest benefit was the relatively rapid removal of difficult contaminants.
Petrox microbes provide quick response surface oil spill bioremediation. Petrox can be applied to the oil surface with a backpack sprayer to initiate rapid bioremediation. This approach protects surface water and vegetation with minimal surface traffic.
In the following example, an oil spill affected the vegetation and surface water at the edge of a lake. Contractors applied Petrox to the oil surface on vegetation and soil. Periodic soil samples tracked the results. After 90 days, the maximum and average concentrations decreased by more than 95% at a very low cost.