Nitrate and Perchlorate Bioremediation in Ground Water

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

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

CL-Out® bioremediation was implemented at a confidential manufacturing site to remediate nitrate and perchlorate concentrations in soil and ground water.  The consultant installed a pump and treatment system that was operated for several years in immediate response to the discovery of contamination. While perchlorate was  the primary contaminant,  the ion-exchange resin became quickly saturated with nitrate, which was present at much higher concentrations than the perchlorate.  After review of various options and completion of a bench-scale test, the consultant implemented in situ CL-Out bioremediation 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  much higher than the perchlorate concentrations and pre-maturely saturated the ion-exchange resin. 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.

The initial application of CL-Out to the soil reduced the perchlorate source concentration.  After eight months of ground water bioremediation, the perchlorate concentration in the unconsolidated aquifer decreased 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 nitrate and perchlorate bioremediation provided immediate risk reduction and mitigated potential off-site migration. The bioremediation contaminant levels to the remediation target in 3 years.  Bioremediation saved 5 years of projected treatment time and millions of dollars in OM & M costs.  The owner sold the property without environmental impairment upon completion of bioremediation. View the full case study  or  a slide presentation.

Project Consultant Received Green Leadership Award

The Massachusetts Department of Environmental Protection awarded Irwin Engineering of Natick, Massachusetts the 2016 Greener Cleanup Leadership Award for the innovative in situ bioremediation of perchorate contamination of soil and ground water at the Concord Road Site in Billerica, Massachusetts. The award honors LSPs and their clients for promoting greener cleanup principles and practices to reduce the overall net environmental footprint of hazardous waste site cleanup response actions under the Massachusetts Contingency Plan.  Read more…

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Bioremediation of Phthalates

Bioremediation of phthalatescan reduce risks to human health and the environment.  Phthalates are a  a family of common industrial chemicals used in plastics and other consume products.  Phthalates can damage the liver, kidneys, lungs and reproductive system.  Petrox microbes can remove these contaminants from water or soil to reduce potential exposure to these risks.

Petrox bioremediation of phthalates has been demonstrated in field and laboratory studies to remove phthalates from soil and ground water.  Field application of Petrox bioremediation reduced bis(2-ethylhexyl)phthalate (BEP) concentrations from 650 ppm to 397  ppm in soil and 300 to 39 ppb in ground water at a site in Rochester, New York.  At the same site di-n-octylphthalate (DOP) in soil was reduced from 7.5 to 1.9 ppm. Click here to view the case study.

PCE Aerobic Bioremediation by Key-hole Source Removal

CL-Out aerobic PCE bioremediation in a keyhole treatmentreduced 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 decreased from 120,000 to 12 ug/L.
  • TCE decreased from 2,000 to 12 ug/L
  • Cis 1,2-DCE decreased 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  incomplete reductive dechlorination by other naturally occuring organisms.

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

  • PCE decreased from 5,000 to 1,600 ug/L.
  • TCE decreased from 43 ug/L to BDL.
  • Cis 1,2-DCE decreased 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 PCE Bioremediation By Cometabolism

CL-Out is a consortium selected for aerobic PCE bioremediation.  CL-Out cometabolizes PCE by growing on a simple sugar and producing a metabolic enzyme to degrade PCE.  The microbes produce a dioxygenase enzyme that breaks the carbon bond in PCE.  This reaction eliminates the biproducts of reductive dechlorination.  Also, the synergistic effect of the CL-Out consortium cometabolizes the full suite of chloroethenes and chloroethanes.

Click here to learn more about CL-Out bioremediation.

Oil-Contaminated Water Treatment

CL Solutions provides a special consortium of microbes for oil-contaminated water treatment.   Under various conditions, the oil removal rate was as much as 1,300 mg/L/day.  In some situations the remediation goal is simply to remove the visible sheen or separate-phase oil.  With aeration, CL Solutions microbes were able to remove the visible oil layer and reduce the TPH concentration from 29% to less than 1% in 30 days at a waste oil lagoon. For more information and other case studies click here.

A special consortium of microbes removed the visible oil layer from this wastewater.

Improving Long-Term Bioremediation Results with Nutrients

The goal of bioaugmentation is to improve the rate of contaminant removal by adding a high population of beneficial microbes to the contaminated media.  The additional microbes  should provide short-term benefit as the microbes begin metabolizing the contaminants immediately upon injection. But what benefit does bioaugmentation provide in the long term? And how much benefit does bioaugmentation provide over biostimulation by adding nutrients to the native organisms?

A client of CL Solutions completed a bench-scale study to answer these questions.  A bench-scale study was preferred to a field study because it removes the potential distribution and time-lag issues associated with the distances between injection and monitoring locations in the field.

Samples of petroleum-contaminated soils were obtained and separated into split samples for treatment with microbes and nutrients. Some were untreated for comparison.  Samples were tested for petroleum concentrations, including C-fraction concentrations after 30, 40 and 60 days.  Heterotrophic populations were measured at 40 and 60 days.

The tests showed the following results in the early stages:

  • All of the treated samples showed more than 80% total petroleum reduction in the first 30 days.
  • The sample treated with nutrients only had the same level of petroleum removal as the bioaugmented samples in the first 30 days.
  • The heterotrophic population of the biostimulated sample was as high as in the bioaugmented samples at 40 days.

After 30 days the situation changed.

  • The bioaugmented microbial population continued to increase  after 40 days and may have increased by a factor of 100 times.  Meanwhile, the biostimulated population appeared to stall.
  • The petroleum removal continued in the bioaugmented samples and reached as high as 93% removal.  In comparison the biostimulated sample stalled at 82% removal.
  • The difference appears to be that the bioaugmented samples removed the C-21 to C-35 concentrations at a much higher rate than the biostimulated sample.
  • Phenanthrene was target chemical for bioremediation. The biostimulated sample showed 39% removal while the bioaugmented samples showed complete removal to BDL.

Overall, the superior performance of the bioaugmented samples appears to be related to having a greater metabolic range that removed the heavier hydrocarbon fractions.  Microbes with the extended metabolic range could continue to multiply as they grew on the heavy hydrocarbon fraction.  The results are consistent with field results showing the recalcitrance of heavier hydrocarbon fractions and compounds like naphthalene and phenanthrene under natural attenuation.

Contact CL Solutions for more information and insights.