Petrox microbe thrive on naphthalene and are very efficient at naphthalene bioremediation in the field. In fact, naphthalene is occasionally used in the QA/QC process to verify Petrox viability and effectiveness. In this test, the Petrox organisms are placed on an agar devoid of a carbon source. The naphthalene is applied to the top plate as the sole carbon source. The Petrox viability is then demonstrated by colony growth on the top plate as shown on the following picture.
Creosote bioremediation was recently demonstrated by a user of a custom blend of CL Solutions organisms. The environmental consulting firm applied the microbes to finely shredded wood that had been saturated with creosote. The initial testing results after bioaugmentation showed a reduction of the creosote concentration by 57% in just 7 days. The concentration measured as total recoverable hydrocarbons decreased from 3,453 mg/kg to 1,497 mg/kg.
The goal of bioaugmentation is to improve the rate of contaminant removal by adding a high population of beneficial microbes to the contaminated media. The additional microbes should provide short-term benefit as the microbes begin metabolizing the contaminants immediately upon injection. But what benefit does bioaugmentation provide in the long term? And how much benefit does bioaugmentation provide over biostimulation by adding nutrients to the native organisms?
A client of CL Solutions completed a bench-scale study to answer these questions. A bench-scale study was preferred to a field study because it removes the potential distribution and time-lag issues associated with the distances between injection and monitoring locations in the field.
Samples of petroleum-contaminated soils were obtained and separated into split samples for treatment with microbes and nutrients. Some were untreated for comparison. Samples were tested for petroleum concentrations, including C-fraction concentrations after 30, 40 and 60 days. Heterotrophic populations were measured at 40 and 60 days.
The tests showed the following results in the early stages:
- All of the treated samples showed more than 80% total petroleum reduction in the first 30 days.
- The sample treated with nutrients only had the same level of petroleum removal as the bioaugmented samples in the first 30 days.
- The heterotrophic population of the biostimulated sample was as high as in the bioaugmented samples at 40 days.
After 30 days the situation changed.
- The bioaugmented microbial population continued to increase after 40 days and may have increased by a factor of 100 times. Meanwhile, the biostimulated population appeared to stall.
- The petroleum removal continued in the bioaugmented samples and reached as high as 93% removal. In comparison the biostimulated sample stalled at 82% removal.
- The difference appears to be that the bioaugmented samples removed the C-21 to C-35 concentrations at a much higher rate than the biostimulated sample.
- Phenanthrene was target chemical for bioremediation. The biostimulated sample showed 39% removal while the bioaugmented samples showed complete removal to BDL.
Overall, the superior performance of the bioaugmented samples appears to be related to having a greater metabolic range that removed the heavier hydrocarbon fractions. Microbes with the extended metabolic range could continue to multiply as they grew on the heavy hydrocarbon fraction. The results are consistent with field results showing the recalcitrance of heavier hydrocarbon fractions and compounds like naphthalene and phenanthrene under natural attenuation.
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A 30 acre bulk fuel facility is ready for reuse after remediation of nearly 100,000 tons of petroleum-contaminated soil in an urban setting near Los Angeles. Bulldog Green Remediation of Walnut Creek, California used a proprietary ex situ treatment process combining Petrox organisms in a custom blend to remediate the soils. All soil was treated and reused on site. This closed-loop process eliminated 8,000 truck loads of soil from the roads and landfills in southern California.
The treatment process reduced contaminant concentrations from typical levels of 1,000 to 10,000 mg/kg to less than 100 mg/kg in less than 30 days. This rapid treatment rate made possible continuous cycling from excavation, through treatment, and back filling.
The site is now ready for reuse as a park and other development.
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.