BTEX Remediation in Groundwater

Success

BTEX contamination in groundwater from a leaking underground storage tank was cost-effectively treated with two applications of Petrox. This project demonstrates the rapid degradation of petroleum components when high populations of Petrox aerobic microbes are injected.

The pre-treatment concentrations of Toluene and Xylene were 1,198ppb and 2,408 ppb, respectively. Ten units of Petrox aerobic microbes were injected into the ground water on about June 2, 2002. Within six weeks the concentrations decreased to 515ppb and 690 ppb, Toluene and Xylene, respectively. After a second inoculation in August 2002, the concentrations decreased to 3.7ppb and 16.4 ppb, respectively. There has been a slight rebound in Xylene to 23.8 ppb, and a third inoculation will be implemented to finish the treatment.

The cost to treat this quarter acre plume with Petrox was about $20,000.

BTEXbio

Bioremediation of BTEX at an Industrial Site in Florida

Background

Petrox® bioaugmentation was used to remediate ground water contaminated by benzene, toluene, ethylbenzene and xylene (BTEX) at an industrial facility in central Florida (Facility ID No. 8521705). The bioremediation was implemented in perimeter wells around the source area where air sparging and vapor extraction was implemented. This combined approach provided cost-effective, full-site remediation by using complementary technologies.

Remediation Approach and Results

Petrox® was introduced into the contaminated ground water in the perimeter of the source area plume by injection through temporary well points. Two applications of Petrox® were completed. The initial application was in December 2007 and a subsequent application was completed in April 2008. During each application 550 gallons of Petrox® microbial slurry were injected into the ground water through 19 injection points. The treatment covered an area of approximately 7,000 square feet.

The ground water treatment results were monitored by laboratory analysis of ground water samples for the contaminants of concern. The quarterly monitoring results after the applications showed an immediate and continuous decrease in the BTEX concentrations. The following chart shows the total BTEX concentrations in three quarterly sampling events after the implementation of Petrox® bioaugmentation.

industrial-site6

Conclusions

This project demonstrates two of the benefits of aerobic bioaugmentation. Petrox® organisms were able to metabolize the BTEX compounds, which were initially at part per million levels, to below detection limits. Bioaugmentation provides active control of the site with hydrocarbon-degrading organisms compatible with air sparging and vapor extraction in the source area, where the contaminant concentrations persisted longer than in the bioaugmentation area.

Petrox Aerobic Bioremediation Degradation of Oil-Field Waste

Success

Petrox is a specialty bioremediation product comprised of patented strains of live vegetative aerobic microorganisms providing fast, effective degradation of petroleum hydrocarbons.

The oil-field pit treatment demonstrates the effectiveness of PETROX to treat oil production wastes encountered during the closure of multiple lagoons in the Southeast. Regulations required oil and grease concentrations below 1% prior to closure. PETROX reduced the petroleum to compliance levels in less than 30 days.
OilFieldSouthE-bar

Pit #

Pit Size

Initial

Final

Treatment Days

1

45’x60’x5’

28.89%

 

0.97%

 

30

2

30’x30’x6’

 

9.48%

 

0.66%

 

20

3

30’x40’x4’

 

4.20%

 

0.71%

 

17

4

30’x30’x5’

 

3.10%

 

0.07%

 

30

5

90’100’x8’

 

1.38%

 

0.88%

 

25

In Situ Bioremediation of Petroleum LNAPL

Background

High concentrations of petroleum in the subsurface can accumulate in a separate liquid phase that floats on the water table, which is referred to as light non-aqueous phase liquid (LNAPL). Investigation and characterization of the extent of separate phase petroleum is challenging. In turn, successful remediation, which depends on accurate and complete site characterization, can be equally challenging. In this case study Petrox® bioaugmentation was used to remove LNAPL and dissolved-phase petroleum to achieve No Further Action status.

Geology and Hydrogeology

The site is located in the Georgia Piedmont where the geology is characteristically weathered granite and saprolite. The petroleum was found in layers of interbedded clay, silt and sand. The first water was encountered at approximately 28 feet below ground surface. The hydraulic conductivity based on slug tests of the impacted zone was 10-4 to 10-5 cm/sec.

The ground water aquifer was naturally aerobic. Dissolved oxygen measurements taken from monitoring wells in the source area ranged from 1.9 to 2.1 mg/L. The oxidation-reduction potential (ORP) measured in the same wells ranged from 241 to 283 mv. The aerobic conditions were not typical of petroleum releases, but favored in situ bioremediation.

During the implementation of bioremediation, the region experienced a drought. The water table dropped below the bottom of some of the monitoring well screens for part of the period. Sampling results may have been affected during the drought, but normal ground water conditions were restored and maintained for the final two years of monitoring.

Contamination

The leaking underground storage tank (UST) was removed and a temporary high-vacuum dual phase extraction system was operated for one day in April 2007. Approximately 50 gallons of petroleum was removed by the high vacuum system. After operation of the high vacuum system was discontinued, the source area total benzene, toluene, ethyl benzene and xylene concentrations was more than 143,000 µg/L and 22 inches of separate phase petroleum was found in a monitoring well outside of the former UST cavity.

The remediation goals were to remove the separate phase product and reduce the dissolved phase BTEX concentrations to below in-stream water standards.

Remediation Approach and Results

The remediation approach was combination of in situ Petrox® bioremediation and periodic liquid phase bailing. It was believed that the petroleum was present in a thin layer, but represented itself as a thicker layer in the monitoring well that intersected the layer. The separate phase was bailed out when it was encountered during monitoring events.

Petrox® bioremediation was used to degrade the petroleum in the ground between the former UST cavity and the impacted down gradient monitoring wells. Petrox® was introduced into the contaminated ground water in three applications by injection through nine temporary well points surrounding the former UST location.

The first injection was 275 gallons of microbial slurry in August 2007. The dissolved phase BTEX concentration decreased by more than 60%. The contaminant concentrations continued to decrease for a year following the first injection. The BTEX concentration was reduced by 90% in that first year. A second injection of 110 gallons of Petrox was completed in September 2008. After one month the BTEX concentrations decreased by 50%. The following table summarizes the treatment and contaminant removal results.

groundwatersampling

The analysis of ground water samples for Pseudomonas sp. by plate count analysis showed the microbial population increased over background levels. The Petrox population maintained an effective level for bioremediation for 6 months to a year following each application.

The separate phase was reportedly no longer present in 2011 and the site received a No Further Action Status designation.

Conclusions

This project demonstrates the benefits of bioaugmentation for high concentrations of petroleum in ground water. Bioaugmentation delivers very high population of effective petroleum-degrading organisms that can be sustained for a long time. The microbes are compatible with bailing out accumulated separate phase from monitoring wells to accelerate the site closure. The total cost for microbes used to close this site was $8,000.

Petrox® Bioaugmentation in Bedrock

Case Study: Petroleum Remediation in Central New Jersey

Summary

Petrox® bioaugmentation was implemented at a petroleum remediation site in Morris County, New Jersey to destroy residual petroleum compounds in ground water. The impacted ground water was in bedrock fractures under and down gradient of a former UST location. The UST was removed and an oxygen release compound was added to the ground water to stimulate bioremediation. However, residual contamination persisted and Petrox® bioremediation was implemented to remove the residual low concentration found at the site.

Geology and Hydrogeology

The bedrock surface was fairly close to the ground surface and the first ground water encountered upon drilling at the site was within the bedrock. Impacted ground water was contained within the fractures near the bedrock surface in a zone estimated to be 40 feet thick.

Contamination

Low concentrations of benzene, xylene, ethylbenzene and toluene were present in ground water at and down gradient of the former UST cavity. The area of proposed treatment was 3,600 square feet.

Implementation

Petrox was applied in two monthly applications of 8 units each. One unit of Petrox® is a 55-gallon slurry with a microbial concentration of 109 cfu/ml. ORC socks were installed in treatment wells to provide an oxygen source for the petroleum metabolism.

The monthly Petrox® injections were on May 29, 2009 and June 26, 2009. Post -treatment samples were taken on June 10, 2009 and May 4, 2010. The following table shows the contaminant concentration treads in the treatment area.

case-study-6-table

Results

The treatment was successful in reducing the BTEX concentration at the site. However, the increase in concentrations after the first treatment showed that there were residual petroleum constituents in the source that was not reflected in the pre-treatment sampling. Petrox® microbes were detected in all of the bedrock sampling points as far as 30 feet down gradient of an injection point. Overall the treatment verified the effectiveness of Petrox® bioaugmentation in fractured bedrock.