Petrox microbe thrive on naphthalene and are very efficient at naphthalene bioremediation in the field. In fact, 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.
CL-Out® was successfully used to remediate solvents in ground water at an operating industrial site in central New Jersey. The the facility was a manufacturing and plating company with historical petroleum and solvent releases.
Chlorinated solvents were found in the ground water in two plumes covering a combined area of about one half acre. The contaminants were a mix of chlorinated solvents including 1,1,1-TCA, 1,1-DCE and PCE in low concentrations. The remediation goal was to reduce the mass of contamination in the ground water plume to prevent mitigate off-site risks.
After the CL-Out application, ground water concentrations in all monitoring wells decreased by more than 80%, which was sufficient to meet the remediation standards. Click here to download a complete case study.
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.
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.
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.
CL-Out bioremediation was used to remediate ground water at an active manufacturing plant in eastern Massachusetts after ISCO treatment of TCE in groundwater reached a limit. CL-Out was selected because the aquifer was naturally aerobic. CL-Out cometabolizes TCE and other chlorinated solvents under aerobic conditions by producing an oxygenase enzyme that breaks the carbon to carbon bond. Under aerobic conditions daughter products such as DCE and vinyl chloride are not formed. 30 days after one application of CL-Out the TCE concentration was reduced by 97% and the site remediation goals were achieved. Click here to download the case study.
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.
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.
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.
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.
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.