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Improving Long-Term Bioremediation Results with Nutrients

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Adding Nutrients Increases Long-Term Population and Bioremediation Results

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.

Contact CL Solutions for more information and insights.

 

 

 

 

 

Land Farming Application Reduces TPH by 90% to 99%

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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.  photo-2              photo-1

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.

land-farming-results

Surface Oil Spill Bioremediation

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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.

Surface Spill Results

Surface Spills to Deep Subsurface Success With Petrox Bioremediation

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Petrox bioremediation is used to remove petroleum contamination from soil and water under many different conditions.  From surface spills to deep soil and ground water contamination, Petrox has successfully removed the contamination and environmental risk.  This summary of case studies demonstrates the applicability of Petrox bioremediation to the full range and life cycle of petroleum spills. Click here to view the document.

 

Fast Bioremediation Eases Site Development in Boston

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Underground storage tank (UST) leaks from a former gas station contaminated shallow ground water under a parking lot for a commercial building.  The UST contamination was found during trenching for utilities.  As the presence of contamination prevented further property development, fast remediation was important to the stakeholders.

The size of ground water plume that resulted from leaching soil contaminants was estimated to be 5,000 square feet.    The contamination was mainly diesel-range petroleum constituents, with the highest concentrations in the aliphatic range, but there were also scattered detections of xylene, toluene, and ethylbenzene.

Petrox bioremediation was implemented in the ground water.  Three units of Petrox (165 gallons) were injected into the contaminated ground water through vertical injection wells located up gradient of the monitoring wells.

After a single inoculation of Petrox, the contaminant concentrations were reduced across the property.  The following table shows the overall reduction in both the volatile and semi-volatile range hydrocarbons.

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