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Florida Site Closures With One Petrox Application

The following applications demonstrate the significant results that can be achieved with a single application of Petrox bioremediation.

Florida Panhandle Gas Station

Facility ID # 32-8520334

Petrox was injected through horizontal drilling to address a ground water plume with limited surface access.  After a single Petrox® application there was significant reduction in the contaminant concentrations.

Sampling Date Benzene Toluene Ethyl benzene Xylene Naph-thalene 2-Methyl naphthalene
Pre- bioaugmentation 11/11/05 4,300 3,000 1,300 5,300 240 48
10/23/07 2,700 4,200 860 5,700 240 41
Post-bioaugmentation 11/06/08 1.7 8.5 0.71 5.1 0.49 0.45
1/22/09 0.88 0.64 0.43 1.3 0.49 0.45

All Concentrations shown in µg/L.

 

Southeast Florida Gas Station

Facility ID 8838788

After removal of USTs, piping and surrounding soils Ground water was treated with 110 gallons of Petrox® by direct injection in June 2009.  Sampling six months after the Petrox® treatment showed significant reductions in all contaminants.

Sampling Date Benzene Toluene Ethylbenzene Total Xylenes
Pre-  bioaugmentation 4/4/2008 480 1800.0 110.0 900.0
Post- bioaugmentation 11/12/09 <0.5 <0.51 <0.44 <0.5

All concentrations shown in µg/L.

 

Southeastern Florida Marina

Tequesta, Florida

Facility ID # 43-8731703

Subsequent to the removal of petroleum underground storage tanks (USTs), piping and surrounding soils for redevelopment, residual soil and ground water contamination at the site were treated with Petrox® bioremediation.  Petrox® was applied to the soil that was removed during the UST removals and to the ground water in the UST cavity.

Approximately 4,000 tons of soil were removed from the excavation and stockpiled on site for treatment.  The total BTEX concentrations in the excavated soil were up to 100 mg/kg.  Petrox® bioremediation was applied to the stockpiled soils.  In less than 90 days the petroleum was no longer detected in the soil and in the soil met the applicable Florida DEP standards.

Petrox® bioremediation was applied to the water in the former UST cavity to treat residual petroleum.  The proximity of the cavity to the Jupiter Sound indicated that the ground water was strongly influenced by infiltration from the Sound.  After less than 90 days post treatment, the water in the excavation also met the applicable Florida DEP standards.

 

Maximum Water Conc. Benzene Toluene Ethylbenzene Total Xylenes
Pre-treatment 1,960 5,140 1,860 18,340
90 days after treatment 3.7 BDL BDL BDL

All concentrations shown in µg/L. BDL= below detection limits.

 

Central Florida Gas Station

Petrox was applied to the ground water in an area around a single monitoring well that did not respond to another treatment as well as the rest of the plume.  A single 10-gallon application of Petrox® was sufficient to apply for site closure.

Sampling Date Benzene Toluene Ethylbenzene Total Xylenes
Pre- treatment 8/2/2007 11,100 1,250 1,260 5,040
Post-treatment 10/4/07 1,600 20.0 290. 840.
11/19/07 0.40 1.0 1.00 32.0

All concentrations shown in µg/L.

 

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.