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What is MEOR?

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MEOR is microbial enhanced oil recovery.  Some microbes produce biosurfactants that increase the water-solubility of oil.  The biosurfactants’ benefit microbes by making it easier for the microbes to metabolize oil.  Additionally, the biosurfactants can strip oil from rock and soil surfaces to improve environmental remediation by extraction, air stripping, or sparging.

The Pseudomonas sp. in Petrox are naturally occuring petroleum-degrading microbes with the broadest metabolic capabilities.  Their production of biosurfactants is one of their features that makes them so effective.  Pseudomonas sp. produce both glycolipid and lipopeptide surfactants.

An initial increase in concentrations may be observed after Petrox is used at a site due to the biosurfactants.  However, the concentrations decrease as the microbes metabolize the oil.  This feature has been used to remove oil safely from inaccessible or sensitive locations such as near utilities, tanks or building structures.

Micorbial Insights, Inc. (micorbe.com) has biosurfactant assays available t0 test for the presence of the genes in Pseudomonas sp. and other organisms that produce biosurfactants.  If tests show that they are abscent from a site, you can enhance the oil recovery with Petrox and the surfactants it produces.

In addition to the biosurfactants that Petrox produces, a non-ionic surfactant is added to Petrox to formulate Petrox EC.  This combination makes Petrox EC a strong cleaning agent to remove oil and grease from surfaces or contaminated subsurface soil or rock.

CL Solutions continues to expand the use of biological products such as Petrox and Petrox EC for bioremediation and microbial enhanced oil recovery.

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.

 

 

 

 

 

Soil Mixing to Improve Distribution of Microbial Solution

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Bioaugmentation results can be accelerated and amplified by soil mixing to improve distribution and contact.  The equipment shown in this example was used to blend Petrox with contaminated soil to a depth of 10 feet.

Soil Mixing Equipment to Improve Microbial Solution Distribution

Soil Mixing Equipment to Improve Microbial Solution Distribution

Click here to view a short video of soil mixing.

Bioremediation of Industrial Fill

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Historical industrial sites often have deposits of fill material containing a wide range of organic contaminants.   Perched ground water  present in the base of the fill is usually impacted by the contaminants and may provide a mechanism for off-property migration of the contaminants.  The organic contaminants are wide spread throughout the fill without a well defined source area.  Cost-effective remediation is difficult with this combination of conditions.

Bioaugmentation with CL-Out or Petrox can remove the contaminants from the fill and perched water by destruction in place.  The organisms in CL-Out and Petrox can metabolize a wide-range of organic chemicals at concentrations from separate-phase layers to part per trillion levels.  Soil and ground water contaminants are addressed simultaneously though injection of the microbes without disturbing the  site operations.

The following table shows typical results from a single application of Petrox to contaminated soil and perched ground water on July 10, 2011.  The remediation progress was tracked by ground water monitoring because it was the easiest sampling method once wells were in place.Industrial Fill TreatmentThe results show that within 30 days the contaminant concentrations in perched water were reduced by 50%.  After 60 days there was slight rebound in come of the contaminants, showing that more soil treatment may be necessary if lower cleanup goals needed to be maintained.

 

 

Field Bioremediation Rates For Petroleum and Solvents

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The success of bioaugmentation depends on effective distribution of the beneficial microbes.  If the target population is achieved, the remediation rate ranges from 50% to over 99% removal.  The rate appears to be independent of the contaminant starting concentrations.  This indepedence is the advantage of bioaugmentation.  Through bioaugmentation the density of beneficial organisms is sufficient for frequent reactions with high or low contaminant levels.  The following chart shows the results of a single application of bioaugmentation at 11 sites in different states, with different contaminants.

remediation rates with bioaugmentation

 

The chart also suggests that the results are not time dependent.  The apparent time independence may be because the reactions are completed early and because these were grid applications with the monitoring locations within the bioaugmented area instead of downgradient where the results would depend on dispersion rates.

The USEPA tested the degradation rate of oil using Munox SR for NCP listing.  The degradation rate exceeded most comparable products with 95% removal of alkanes and 89% removal of aromatics in 28 days.  The NCP test results are available at https://19january2017snapshot.epa.gov/sites/production/files/2013-08/documents/notebook.pdf