Nitrate and Perchlorate Bioremediation in Ground Water

In Situ Bioremediation Eliminated Pump and Treat and Ion-Exhange Treatment Cost 

Site closure reached in less than half the time and at less than half the cost

CL-Out® bioremediation was implemented at a confidential manufacturing site to remediate nitrate and perchlorate concentrations in soil and ground water.  A pump and treatment system was installed and operated for years in immediate response to the discovery of contamination. While perchlorate was considered the primary contaminant,  the ion-exchange resin became quickly saturated with nitrate, which was present at much higher concentrations than the perchlorate.  In situ bioremediation was implemented to reduce the on-going cost of ground water extraction and treatment.

One of the key factors in CL-Out® cometabolism of perchlorate at this site was that CL-Out® organisms were able to reduce sequentially the oxygen and nitrate prior to perchlorate. The initial nitrate concentrations were typically much higher than the perchlorate concentrations. The perchlorate concentration did not decrease until the nitrate concentration decreased to less than the perchlorate concentration. One of the benefits of the CL-Out® organisms was this ability to utilize these different electron acceptors.

In eight months, the perchlorate concentration in the unconsolidated aquifer was reduced from 128 mg/L to 3.4 mg/L immediately down gradient of the source area and from 220 mg/L to 39 mg/L farther down gradient.

Simultaneously, the CL-Out® microbes also removed the nitrate. Down gradient of the source area the nitrate concentration decreased from 105 mg/L to <1.0 mg/L.  Farther down gradient the nitrate concentration decreased from 200 mg/L to 5 mg/L.

The in situ bioremediation provided immediate risk reduction and mitigated potential off-site migration. The contaminant levels were reduced to the remediation target in 3 years, saving 5 years of projected treatment time and millions of dollars in OM & M costs.  The property sold without environmental impairment upon completion of bioremediation.

 

 

 

 

Aerobic PCE Cometabolism

Pilot Study Confirms Aerobic Cometabolism of PCE at Kentucky Site

A CL-Out bioremediation pilot study confirmed the PCE could be removed from ground water by aerobic cometabolism.  The pilot study was at the former location of a dry cleaners where PCE wasfound in ground water at 27 parts per billion (ppb).  CL-Out micorbes and dextrose as the metabolic substrate were injected into the ground water upgradient from the sentinal monitoring well.  After 30 days the PCE concentration decreased to 20 ppb.  After 6 months the PCE concentration decreased to 16 ppb.

As the PCE was decreasing the site conditions stayed aerobic.  The dissolved oxygen level in ground water decreased 1.07 mg/L to 0.71 mg/l and the ORP decreased from 99 to 45 mv.

CL-Out cometabolism used a dioxygenase enzyme that is produced constituatively as the metabolic substrate is consumed.  The dioxygenase enzyme destabilizes the carbon bond in the PCE to convert the molecule to an organic acid that leads to complete mineralization.

 

 

Keyhole Treatment – Cost Effective Plume Treatment Through Source Removal

CL-Out bioremediation was used in a keyhole treatment to reduce the mass of contamination near the source and down gradient concentrations in the plume.  At a former manufacturing facility in Ohio the concentration of PCE near the source was over 100,000 ug/L.  Down gradient of the source the PCE concentrations were less than 10% of the source concentration.  Aggressive treatment in the source area reduced the source concentration and in the down gradient plume.

Source area concentrations decreased as follows after one treatment with CL-Out bioremediation:

  • PCE was reduced from 120,000 to 12 ug/L.
  • TCE was reduced from 2,000 to 12 ug/L
  • Cis 1,2-DCE was reduced from 9,500 to 8,100 ug/L.
  • Vinyl chloride, however, increased from 1,200 to 22,000 ug/L.

The vinyl chloride increased as the aggressive cometabolic treatment stimulated some incomplete reductive dechlorination.

Down gradient from the source, the concentrations decreased with slight to no increase in daughter products.  The following results were measured in the down gradient plume:

  • PCE reduced from 5,000 to 1,600 ug/L.
  • TCE reduced from 43 ug/L to BDL.
  • Cis 1,2-DCE was reduced from 140 to 23 ug/L.
  • Vinyl chloride  was not detected before or after treatment.

Keyhole treatment was a cost effective approach to reducing the mass of contamination in a ground water plume by focusing aggressive treatment on the source area.  Concentrations in the rest of the plume decreased as the microbes and treated water dispersed through the plume.

Aerobic Cometabolism of TCE and 1,4-Dioxane – Field Demonstration

In a pilot study to compare aerobic cometabolism with anaerobic reductive dechlorination  to remediation TCE and 1,4-dioxane at a former industrial facility in New Jersey, aerobic cometabolism reduced the concentrations of both compounds while anaerobic reductive dechlorination was unsuccessful.  For aerobic cometabolism, CL-Out microbes were injected into the aquifer to a depth of 60 to 90 feet below ground.  The pilot treatment area was 500 square feet.  Monitoring wells were placed upgradient, sidegradient and downgradient of the injection point.  Ground water samples were taken on a monthly basis for 9 months.

The results showed that complete TCE mineralization, without the production of daughter products, was measured within the first month.  CL-Out bioremediation removed 80% of the TCE at 40 feet downgradient in less than three months.  CL-Out bioremediation reduced the 1,4-dioxane concentration to below detection limits at 20 and 40 feet downgradient in the first month.

Click here to view a summary case study.

 

 

1,1,1-TCA Bioremediation at an Industrial Site in Dayton, Ohio

CL-Out bioremediation reduced the concentration of 1,1,1-TCA in ground water at a steel manufacturing facility in Dayton, Ohio. Following implementation of ozone treatment and high vacuum extraction for more than 2 years, the contaminant concentrations remained high.  Bioaugmentation followed up on these treatments and reduced the 1,1,1-TCA concentration very quickly.  Within 30 days of bioaugmentation, the source area contaminant concentration decreased by 80%.  After a second application, the concentration decreased from the pre-treatment concentration of 1,100 ug/L to 1.4 ug/L.  The bioaugmentation effect was observed as far as 250 feet downgradient where the concentrations decreased by more than 50%.  Click here for the full case study.