Demonstration of Dry Cleaner PCE Bioremediation in Vermont

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Cl-Out bioremediation at a dry cleaner in Vermont demonstrated bioremediation of PCE in aerobic ground water.  CL-Out microbes were selected for bioremediation of the site because they are compatible with the natural aerobic aquifer conditions.  One application of CL-Out bioaugmentation reduced the PCE concentration by 90% in less than 6 months without increasing the vinyl chloride concentrations.

Sampling Results

The pre-bioaugmentation sampling showed aerobic conditions (DO 1.2 mg/L and ORP 108) and a low population of Pseudomonas microbes (2,000 cells/ml).  After bioaugmentation the Pseudomonas population was greater than 300,000 cells/ml.  As the microbes consumed the dextrose substrate and produced the oxygenase enzymes necessary for PCE destruction, the ORP and PCE concentrations decreased to -236 and 0.89 mg/L, respectively.  Six months after the bioaugmentation, the microbial population returned to the pre-bioaugmentation conditions (5,000cells/ml).

The bioaugmentation reduced the PCE concentration from 219 ug/L to 22.3 ug/L.

Field Bioremediation Rates For Petroleum and Solvents

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The success of bioaugmentation depends on effective distribution of the beneficial microbes.  If the target population is achieved, the remediation rate ranges from 50% to over 99% removal.  The rate appears to be independent of the contaminant starting concentrations.  This indepedence is the advantage of bioaugmentation.  Through bioaugmentation the density of beneficial organisms is sufficient for frequent reactions with high or low contaminant levels.  The following chart shows the results of a single application of bioaugmentation at 11 sites in different states, with different contaminants.

remediation rates with bioaugmentation

 

The chart also suggests that the results are not time dependent.  The apparent time independence may be because the reactions are completed early and because these were grid applications with the monitoring locations within the bioaugmented area instead of downgradient where the results would depend on dispersion rates.

The USEPA tested the degradation rate of oil using Munox SR for NCP listing.  The degradation rate exceeded most comparable products with 95% removal of alkanes and 89% removal of aromatics in 28 days.  The NCP test results are available at https://19january2017snapshot.epa.gov/sites/production/files/2013-08/documents/notebook.pdf

 

Bioremediation of Dinitrotoluene

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Dinitrotoluene (DNT) may occur in soil and ground water as the result of spills and historical use of the chemical as a solvent and industrial intermediary or as a residual of explosives at military facilities.  CL Solutions and SpecPro, Inc. conducted a treatability study to determine the effectiveness of CL-Out microbes in the removal of DNT from contaminated ground water at the Badger Army Ammunition Plant (BAAP) near Baraboo, Wisconsin.  The treatability study showed the removal of all six isomers of DNT, with a 53% to 91% removal in 21 days.  Intermediate by-products were detected only temporarily during the treatability study.  For more detailed information call CL Solutions.

Push-Pull Application of Aerobic Cometabolism

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A CL-Out bioremediation push-pull pilot study was implemented  at a confidential dry cleaners site to verify the applicability of CL-Out bioremediation.

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 1,000,000 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.   The post-treatment sample was taken after the monitoring well was purged of the injected volume.

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.

CL-Out Bioaugmentation Saves Time and Money

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By switching from active extraction to in situ CL-Out® bioremediation, In Control Technologies, Inc. of Houston, Texas saved their client $100,000s in on-going operation and maintenance costs.  The Site was a shopping center where soil and ground water were contaminated by dry cleaning chemicals.  A dual phase extraction system was installed and operated for 9 years.  The dual phase system reduced the total CVOCs by 70%, but the contaminant removal rate  reached the limit of cost effectiveness.

By switching to bioremediation, the client avoided $75,000 on-going annual operation and maintenance cost with a $20,000 investment in bioremediation. CL-Out® bioremediation reduced the residual contamination by more than 98% in less than 90 days.  This case study was reported at the 9th In Situ and On-Site Bioremediation Symposium, 2007

Irwin Engineers, Inc., of Natick, Massachusetts has undertaken a similar approach to reduce on-going pump and treat remediation costs at a site of perchlorate contamination.  Irwin Engineering presented that case study at the AEHS Soils, Sediment, Water and Energy Conference (2013).