Bioremediation of 1,1,1-Trichloroethane and 1,1-Dichloroethene at a Confidential Site

Background

CL-Out® bioaugmentation was used to remediate ground water contaminated by 1,1,1-trichloroethane (1,1,1-TCA) and 1,1-dichloroethene (1,1-DCE). The 1,1-DCE was formed as a product of the natural abiotic degradation of 1,1,1-TCA. The bioremediation was implemented as a pilot study and a subsequent interim action for source removal.

Remediation Approach and Results

CL-Out® was introduced into the contaminated ground water in the suspected source area by injection through temporary well points up gradient of the monitoring point. The initial application was in March 2007 and a subsequent application was completed in September 2007.

The ground water treatment results were monitored by analysis of ground water samples for the contaminants of concern. The 30-day monitoring results after the first application showed an immediate decrease in the contaminant concentrations. After 30 days, the 1,1,1-TCA concentration decreased from 1,000 µg/L to 190 µg/L and the 1,1-DCE concentration decreased from 160 µg/L to 27 µg/L . Long-term monitoring after the second application showed that the concentrations of both compounds were reduced to 1.4 µg/L. The following chart shows the long-term contaminant concentrations.

chart_industrial_TCA_DCE

Conclusions

This project demonstrates several of the benefits of aerobic bioaugmentation. CL-Out® organisms were able to metabolize the parent chloroethane compound and the daughter product, which was a chloroethene compound. The metabolic diversity of the CL-Out® organisms facilitates enables the bioremediation of mingled plumes and multiple contaminants. Bioaugmentation provides active control of the site as effective organisms compatible with the site conditions were injected where they were needed for quick contaminant removal.

Fast Dry Cleaner Bioremediation

Case Study: Dry Cleaners Site, Southern California

Site Summary

CL-Out® fast dry cleaner bioremediation cost-effectively removed solvents from soil and ground water at a site in Soutern California.  After one application of CL-Out® bioremediation, the total chlorinated solvents concentration in ground water decreased by 90%. At the same time, the contaminant concentrations in soil decreased by an average of 85%. The remediation provided immediate risk reduction including avoiding vapor intrusion by vinyl chloride

Project Design and Implementation

Investigation found dry cleaning solvents in soil and groundwater around a dry cleaning machine. The solvent entered the soil below the building and percolated through the soil to a perched ground water.  The soil and sediments are interbedded alluvial and marine sediments with a high permeability.   The impacted soil volume covered approximately 80 cubic yards. The area of ground water impact and treatment covered approximately 2,000 square feet.

Based on the volumes of impacted soil and ground water, the remediation plan included five drums of hydrated CL-Out®.  Two drums treated the soil and perched ground water beneath the dry cleaning machine. Three drums treated the deeper ground water in the diffused area of the plume. The total injection volume was less than .1% of the pore volume of the treated soil and ground water.

CL-Out® bioremediation destroys chlorinated solvents by aerobic cometabolism. Dextrose provided the carbon source to support microbial growth. EHC-O by Adventus maintained the aerobic conditions to support cometabolism and prevent potential production of vinyl chloride.

Fast Dry Cleaner Bioremediation Results

Post–treatment soil and ground water sampling was approximately 30 days after the injection. The post-treatment soil samples came from locations adjacent to pretreatment sampling locations. The shallow soil samples all showed a decrease in solvent concentrations and no generation of vinyl chloride. Post-treatment ground water samples came from existing monitoring wells. The perched ground water showed a decrease in PCE concentrations but a slight increase in TCE and DCE concentrations. The deeper ground water showed a decrease in all concentrations. Vinyl chloride was not detected in either the perched or deep ground water. The following table shows the fast dry cleaner bioremediation results.

dry_cleaner_chart 6_11

The 30-sampling results show that the site progressing toward fast closure. Additional ground water treatment is unlikely to be necessary to achieve site closure after sufficient post-treatment monitoring.

Click here to learn more about CL-Out bioremediation.

Remediation of an Industrial Dry Cleaning Site

Site Summary

A CL-Out bioaugmentation pilot study verified the applicability of CL-Out remediation of an industrial dry cleaning site. The pilot study also determined whether the availability of oxygen to support cometabolism would limit the bioremediations.

Geology and Hydrology

Although the impacted ground water was relatively shallow, the site geology was complicated and varied across even this small site. In general the glacial deposits at the site were mainly till with interbedded sandy and silty zones. The impacted ground water was contained within the granular deposits.

Contamination

The main ground water contaminant was PCE with lower concentrations of TCE, cis -1,2 DCE and vinyl chloride. In the pilot study area, the PCE concentration was 44,200 μg/L and the total of the daughter products was 14,750 μg/L.

Pilot Study Design

A pilot study was completed in the source area in the fall of 2009. One unit of CL-Out was injected into the affected ground water in the source area. One unit of CL-Out is a 55-gallon slurry with a microbial concentration of 109 cfu/ml. The CL-Out microbes were injected with 50 pounds of dextrose to provide a carbon source to support the energy requirements of the population. Pre- and post -treatment samples were taken on February 19 and December 10, 2009. The post-treatment sample was taken after the monitoring well was purged of the injected volume. The following table shows the contaminant concentration trends in the treatment area.

dryclean8

Results

The pilot study verified the applicability of CL-Out bioremediation to the site. The total concentration of CVOCs was reduced from 59,000 to 13,740 μg/L. The CL-Out bioremediation was most effective in the removal of PCE and TCE. There was an increase in vinyl chloride suggesting some incomplete reductive dechlorination, probably by native dehalogenating organisms. Full-scale treatment will be most effective with the addition of an oxygen supplement to limit the dehalogenation and promote the cometabolism of the daughter products. Overall the push-pull pilot study verified the effectiveness of CL-Out bioremediation and provided insights for making full-scale application more effective.

Bioremediation of Chlorobenzene Following ISCO

Compatable Techology To Finish Remediation

CL-Out® micorbes bioremediation of chlorobenzene continued treatment after ISCO remediation stalled.  The target isomers included chlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, and 1,2-dichlorobenzene. Before bioaugmentation, individual concentrations exceeded 50,000 µg/L. The CL-Out® treatment quickly reduced contaminant concentrations by as much as 82% more.

Remediation Approach and Results

Injection through temporary well points introduced CL-Out® micorbes into the contaminated ground water in November 2010. Only one drum of the CL-Out® was injected into the ground water.

The ground water monitoring included analysis of ground water samples for the contaminants of concern, microbial population, and known functional genes, including naphthalene dioxygenase, phenol hydroxylase, and toluene dioxygenase. The 30-day monitoring results show an immediate decrease in the contaminant concentrations. After 30 days, bioremediation reduced 62% to 82% of individual contaminants. The sampling results 30 days after bioaugmentation are compared to the pre-treatment concentrations on the following chart.

isco-1

The total biomass increased from 1.5 million to 12.8 million cells per milliliter following the bioaugmentation. The concentration of the naphthalene dioxygenase functional gene also increased by more than ten fold, as shown on the following table.

isco-2

Conclusions

This project demonstrates several of the benefits of bioremediation of chlorobenzene. Bioaugmentation provides active control of the site as effective organisms compatible with the site conditions were injected where they were needed. Furthermore, the CL-Out® aerobic cometabolism was compatible with the residual conditions following ISCO treatment. Treatment will continue to reduce the contaminant concentrations to acceptable levels.

Click Here to read more about CL-Out bioremediation.