Vermont Dry Cleaner Remediation Using CL-Out

Cl-Out bioremediation was used to remove PCE from ground water at a dry cleaners in Vermont.  CL-Out micorbes 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.

The following table summarizes the process of aerobic cometabolism of PCE.  The pre-bioaugmentation sampling showed aerobic conditions and a low population of Pseudomonas microbes.  After bioaugmentation the Pseudomonas population was higher.  As the microbes consumed the dextrose substrate and produced the oxygenase enzymes necessary for PCE destruction, the ORP and PCE concentrations decreased.  Six months after the bioaugmentation, the microbial population returned to the pre-bioaugmentation conditions.

Aerobic CL-Out Cometabolism Tracking

Improve Soil Flushing and LNAPL Removal with Petrox EC

Petrox EC is a product that combines a surfactant with petroleum-degrading microbes to improve separate phase oil recovery and bioremediation of residual oil.  The combined approach improves the rate of oil removal from soil and other subsurface media and establishes a beneficial petroleum-degrading microbial population that will treat tightly bound or deeply penetrated oil.

Petrox EC has been used in combination with periodic LNAPL extraction by pumping or bailing.   In field applications the surfactant effect has increased the LNAPL recovery rate by more than 10 fold.

Petrox EC has also been used to improve the efficiency of air sparging by flushing oil from the sediment surface for sparging and vapor phase recovery.

Field Bioremediation Rates For Petroleum and Solvents

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

 

Push-Pull Application of Aerobic Cometabolism

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.

Switching to In Situ Aerobic Cometabolism Saves Client $100,000s

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).