Naphthalene Bioremediation With Petrox Microbes

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Naphthalene is often a recalcitrant petroleum compound that keeps sites from clean closure.  This resistance to remediation is due to naphthalene’s relative high adsorption and low solubility rates.  Naphthalene has an aqueous solubility of 3.1E1 mg/l compared to benzene at  1.75E3 mg/l .  Naphthalene has an affinity of adsorption expressed as the octanol/water partition coefficient  (log Kow) of 3.26, while benzene has a log Kow of 2.13.  For further comparison, acetone has a high water solubility at 1E6 mg/l and low log Koc of -0.24.  In a study of relative degradation rates, the USEPA found a first order kinetic constant of 14.0 L/hg for naphthalene and 0.234 for benzene in activated sludge.  Despite these challenges,  naphthalene bioremediation with Petrox microbes has been successful at many spill sites.

Microbes initiate metabolism of naphthalene by inserting two oxygen atoms into the naphthalene structure.  This initial step is catalyzed by naphthalene dioxygenase.  Tests of sites inoculated with Petrox microbes show naphthalene dioxygenase at 1E8 to 1E10.

Petrox microbes thrive on naphthalene to the extent that 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.

Click here and here to view cases studies of naphthalene bioremediation case studies.

Case Study:
Orange County Fire and Rescue Station 81, Orlando, Florida

Oculus Number 8520434

Petrox was used to treat the residual petroleum contamination in ground water after the leaking tank was removed.  The petroleum contamination exceeded applicable standards for benzene, toluene, ethylbenzene, and xylene (BTEX) and naphthalene.  Petrox was injected into the ground water through 28 injection points covering a plume area of approximately 6,300 square feet.   Petrox injections were completed on June 18, September 11, and November 1, 2002.

Prior to bioaugmentation 100 pounds of ORC was added to provide supplemental oxygen for the bioremediation.  After verifying the dissolved oxygen concentration was more than 1.0 mg/l, the site was ready for bioaugmentation.

During the first injection 10 drums of Petrox were injected to cover the full plume.  As the area of contamination decreased, less Petrox was injected.  Five drums were injected in a focused application on September 11 and November 1, 2002.

Quarterly monitoring was completed during and after the inoculation to determine the bioremediation results.  The cleanup goals were achieved in the source area after the first inoculation.  The contamination persisted, however, in the down gradient wells.  The cleanup goals were achieved in the down gradient monitoring well after the third injection, but there was subsequent rebound.  After full distribution of Petrox was reached throughout the plume, the BTEX and naphthalene bioremediation achieved  cleanup goals.

Please refer to the table below for the ground water monitoring results.

Monitoring Well Date Benzene Toluene Ethylbenzene Total Xylenes Naphthalene
MW-7 Source Area 6/12/2000 5.0 46.0 18.0 90.0 24.0
6/13/2001 39.0 272.0 167.0 526.0 26.0
3/14/2002 21.0 19.0 102.0 266.0 39.0
6/5/2002 ORC Added
6/18/02 10 Drums of Petrox Added
7/14/2002 <1.0 <1.0 <1.0 <2.0 <1.0
9/11/2002 <1.0 <1.0 <1.0 <2.0 <1.0
9/11/02 5 Drums of Petrox Added
10/7/2002 <1.0 <1.0 <1.0 <2.0 <1.0
11/1/02 5 Drums of Petrox Added
12/2/2002 <1.0 <1.0 <1.0 <2.0 <1.0
1/9/2003 <1.0 <1.0 <1.0 <3.0 <5.0
4/17/2003 <1.0 <1.0 <1.0 <2.0 <1.0
             
MW-8

Down Gradient

 6/12/2000 2.0 72.0 21.0 109.0 39.0
6/13/2001 14.8 677.0 207.0 1292.0 113.0
3/14/2002 71.0 1198.0 357.0 2408.0 193.0
6/5/2002 ORC Added
6/18/02 10 Drums of Petrox Added
7/15/2002 19.0 515.0 170.0 690.0 39.0
9/11/2002 <1.0 3.7 3.8 16.4 <1.0
9/11/02 5 Drums of Petrox Added
10/7/2002 6.4 2.3 4.7 23.8 15.0
11/1/02 5 Drums of Petrox Added
12/2/2002 38.0 515.0 95.0 460.0 10.0
1/9/2003 <1.0 <1.0 <1.0 <3.0 <5.0
4/17/2003 <110.0 1060.0 285.0 1120.0 65.0
4/29/2004 <1.0 <1.0 <1.0 <1.0 <1.0
9/1/2004 <1.0 <1.0 <1.0 <1.0 <1.0
12/1/2004 <1.0 <1.0 <1.0 <1.0 <1.0
3/21/2004 <1.0 <1.0 <1.0 <1.0 <1.0

Contact CL Solutions for a free consultation to find out whether bioremediation is right for your site.

Case Study: Horizontal Injection for BTEX and Naphthalene Remediation

In situ remediation is a contact sport, requiring contact between the microbes and contamination.  Clay-rich soils are particularly challenging as the low permeability limits effective distribution of inoculants.  While numerous closely-spaced injection points can improve the distribution of inoculants, this approach is often not possible at active properties and can be costly.  Horizontal drilling was used on the subject site to overcome the combined challenges of low permeability and limited site access to inject Petrox® microbes for bioaugmentation.  The combined technologies reduced the total BTEX concentrations in ground water from 2,771 µg/L to 645 µg/L in less than one year.

Background

The site is a former gas station located in the Florida panhandle.  The site soils are mixed silt and clayey silts that are typical of the coastal setting.  The depth to the water table varied seasonally from 13 to 18 below ground surface.

The underground storage tanks and contaminated soil had been removed prior to the ground water treatment.  Residual ground water contamination exceeded Florida Ground Water Cleanup Target Levels (GCTLs) for benzene, toluene, ethylbenzene, xylene, naphthalene and methylnaphthalene isomers.

The proposed treatment area was approximately 2,500 square feet.  The treatment depth was from 10 to 25 feet below grade.  The treatment depth included the capillary fringe to treat residual contamination above the seasonal low water table.

Horizontal Injection

 Access to the treatment area was limited by the current property use, the proximity of roads on two sides and a building on the third.  Horizontal drilling was selected by the site consultant, Advanced Environmental Technologies (www.aetllc.com) to deliver Petrox® to the contamination.

The horizontal drill rig was set back from the treatment zone on the opposite side of the building.  The horizontal injection wells were set in four horizontal sets of eight wells. The horizontal layers were at 10, 15, 20 and 25 feet deep.  The wells in each layer were five feet apart.  A total of 32 injection wells were closely spaces for excellent coverage through the treatment zone.

Petrox® was injected into the ground water in two treatment events – November 6, 2008 and June 24, 2009.  Petrox® was delivered in each injection well as the drill stem was withdrawn through the treatment zone.  The injection was monitored for accuracy so that 0.2 gallons of Petrox® was injected per foot of injection zone.  A total of 320 gallons of Petrox® slurry was injected.

Following the Petrox® injection, air was injected periodically through vertical sparging wells to increase the oxygen availability for the microbial metabolism.

Results

Ground water samples were collected from a monitoring well inside the treatment area to track the progress of the bioremediation.  Approximately 60 days after the first Petrox® treatment, analysis of ground water samples showed 84% reduction in the benzene concentration and 35% reduction in the total BTEX compounds concentrations.  There was an apparent increase in the xylene concentration due to ground water mixing and induced increase in solubility due to the bioaugmentation injections.

A second sampling event approximately 30 days after the second injection showed additional reduction in the contaminant concentrations.  After the second injection, the total BTEX concentrations were 23% of the original concentration with xylene decreasing from 1,200 to 95 µg/L.

In addition to the BTEX compounds, naphthalene and methylnaphthalene isomer concentrations decreased through both treatments.

Sampling Date Benzene Toluene Ethylbenzene Xylene Naphthalene
Pre-treatment 11/11/05 3,000 42 1,100 1,100 230
10/23/08 1,700 18 460 454 280
11/6/08 1,600 41 370 760 310
Post-treatment

 

 1/22/09 420 43 140 1,200 43
7/30/09 490 2.6 57 95 55

Conclusions

Horizontal drilling and injection made it possible to remediate ground water at this site of petroleum contamination with limited access and low natural permeability.  Without disturbing the property use, the horizontal injection of Petrox® provided effective distribution of the microbes for bioremediation.  The injection may have also made the contamination more available for bioremediation by increasing the contaminant solubility as shown by temporary increases in concentration.

This case study demonstrates that in situ bioaugmentation may be a feasible solution for sites with limited permeability and access restrictions.  For more information contact CL Solutions at www.cl-solutions.com.

Case Study: South Carolina Industrial Site

Petrox microbes were injected in a petroleum ground water plume for naphthalene bioremediation to remove contamination at an industrial site.  With one application, the petroleum constituents were below detection limits in under six months.

  Sampling Date Benzene

(ug/L)

 Toluene

(ug/L)

 Ethylbenzene

(ug/L)

 Xylene

(ug/L)

 Naphthalene

(ug/L)
Pre-Injection 1/8/14 210 1,100 180 3,500 530
30 Days After 4/25/14 58 300 28 1,100 65
6 Months After 9/3/14 <0.2 <1.7 <1.7 <1.7 <1.7

Petrox is a blend of  Pseudomonas sp. formulated to degrade a wide range of petroleum hydrocarbons including BTEX and naphthalene bioremediation.  The application of Petrox at the case study site overcame some of the recalcitrance of xylenes and naphthalene that can result in slow remediation.

Case Study: Petrox and Methylnaphthalene Isomers Bioremediation 

Petrox microbes accelerated BTEX and methylnaphthalene bioremediation at a former fueling station in Florida.  After a leaking tank underground storage tank (UST) was removed,  the consultants injected Petrox micorbes into the groundwater. A temporary well showed high concentrations of BTEX, methylnaphthalene isomers, and total recoverable petroleum hydrocarbons (TRPH) in the former tank location.  A permanent monitoring point replaced the temporary well. Since the contaminants were not detected outside of the UST cavity, the treatment focused on the cavity and its proximity. The consultant injected Petrox  into the ground water through 12 direct-push injection points in and around the UST cavity. They used approximately 10 gallons of Petrox solution at each of the injection points in August 2001. After one injection of Petrox, petroleum hydrocarbons concentrations decreased below detection levels in the UST cavity.  Please refer to the table below for the ground water monitoring results.

Persistence in Soil and Low Ground Water Concentrations

Methylnaphthalene and naphthalene persist in soil after other volatile components of fuels are gone.  The persistence comes from to their relatively high affinity for adsorption to soil and relatively low water solubility.  These factors account for the common rebound of ground water concentrations. Despite high concentrations of naphthalene and methylnaphthalene in soil near the ground water table, often the dissolved  concentration in the ground water is very low.  The accumulation of these compounds at the water table causes a problem for remediation.  Frequently after ground water remediation, seasonal fluctuation of the water table through the contaminated vadose zone recharges the concentrations of these compounds.  This results in seasonal fluctuation in the ground water concentrations.

Methylnaphthalene Metabolism

The microbes in Petrox  accelerate the remediation because they product an extracellular biosurfactant that desorbs the methylnaphthalene to make it available for extraction or for in situ bioremediation.  At this site, the contaminated soil was removed to the water table, so concentrations did not rebound after the initial ground water remediation.  At other sites where Petrox bioremediation addressed methylnaphthalene or naphthalene, the consultant combined bioremediation with extraction.  The combined technologies removed the contamination flushed from the soil in addition to the bioremediation.  Click here to view case studies from other sites.

Methylnaphthalene Bioremediation

In Situ TPH Bioremediation with Petrox

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With Petrox microbes, in situ TPH bioremediation reduced the concentration of petroleum in soil at a former gas station from 9,500 mg/kg to 52 mg/kg. The impacted soil was at more than 20 feet deep.  Injection of calcium peroxide provided the oxygen needed for metabolism of the petroleum by Petrox microbes.  The post treatment sampling was 90 days after the bioaugmentation, so that even though the average remediation rate was 105 mg/kg/day, the peak remediation rate must have been much higher when the Petrox population was higher.

This is another example of fast, reliable bioremediation by Petrox organisms.

In-situ Bioremediation of BTEX, TPH and PAHs in Groundwater

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Summary

In situ bioremediation reduced ground water contamination by more than 99% in less than a year at a gas station in Florida.

Convenience Store in Florida

After three underground storage tanks were removed from the location of a convenience store, investigation showed that petroleum contamination was present in small area near the former dispenser island.  The vadose-zone contaminated soil was excavation and disposed off-site.  Ground water monitoring showed that the ground water impact was limited to a small area near the source of contamination. The decision was made to close the site by applying Petrox® bioremediation to the ground water.

Ground Water Contamination

The ground water contamination was in a shallow water table aquifer that had a medium permeability.  The contamination was a suite of BTEX, PAHs, methylnaphthalene isomers and TRPH.

Bioremediation

A pilot study was completed to determine feasibility of Petrox bioremediation combined with a peroxide oxygen supplement.  The pilot study reduced contaminant concentrations by up to 92%.  A full-scale application completed the site remediation.

Results

The pilot study and full-scale applications of Petrox and an oxygen supplement reduced BTEX compounds by >99%, naphthalene by 99%, TRPH by 96% and naphthalene isomers by 88% to achieve the remediation goals and site closure.  The microbial cost for the pilot study and full-scale treatment was less than $2,000.

To learn more, click here to download the case study.

Improving Long-Term Bioremediation Results with Nutrients

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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.

 

 

 

 

 

PAH Bioremediation

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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.