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.






Pesticide Bioremediation – Landfarming Application for DDD, DDE and Toxaphene

Petrox® bioremediation was used to remediate pesticide-contaminated soil at an industrial location in California.

Soil Remediation

The soil contamination consisted of pesticides including 4,4-DDD, 4’4-DDE and toxaphene.  Soil samples were sent to CL Solutions for bench-scale treatability studies.   The following table shows the  maximum detected concentrations and the treatment results.

Untreated Concentrations (ug/Kg)
Post-treatment concentrations (ug/Kg)

After the bench-scale verification, full-scale bioremediation was implemented.  The contaminated soil was placed in two stockpiles and treated with Petrox. The following table shows the pre- and post-treatment results.

Contaminant Concentrations (ug/Kg)
Pile 1
Pile 2
nd ( <5)
nd  (<5)
nd (<5)


The Petrox treatment successfully reduced the concentrations of pesticide contaminants in the soil stockpiles.  For additional information or assessment of applicability to your site contact CL Solutions.

In Situ CL-Out Bioremediation of Industrial Solvents

Case Study :

Industrial Manufacturing Site, Illinois

Remediation Summary

Leaks from an aboveground solvent tank impacted soil and ground water quality at a manufacturing site in Illinois.  The impact was found under the adjoining building as well as the area near the tank.  The soil and ground water were treated in situ with CL-Out® bioremediation microbes.  Through cometabolism CL-Out® microbes reduced the contaminant concentrations to acceptable levels in less than one year.

Contaminants Soil Results (mg/Kg) Ground Water Results (mg/L)
Pre-Treatment Post- Treatment Pre-Treatment Post- Treatment
PCE 41.8 1.69 5.59 0.006
TCE 4,670 632 15.6 0.026
Cis 1,2-DCE 171 56.6 7.43 0.029
Vinyl Chloride BDL BDL 0.095 0.013

Implementation and Results

Soil Type:  Silty clay till

Treatment Area:  15,000 sq. ft.

Unsaturated soil thickness:  16 ft.

Saturated aquifer thickness:  5 ft.

Treatment: Two applications, initial treatment with 13 units of CL-Out® and follow up treatment with 5 units.

Product Cost: $30,000


CL-Out® bioremediation quickly and cost-effectively reduced the contaminant concentrations to acceptable levels.  Through cometabolism the parent and daughter products were removed simultaneously.  CL-Out® bioaugmentation accelerated the site remediation and reduced uncertainty by applying the right microbes where they were needed.

Aerobic Cometabolism of PCE at an Industrial Site in Tampa, Florida

Project Summary

Degreasing solvents were found in the ground water at an industrial manufacturing facility in Tampa, Florida.  The solvents include PCE and its associated breakdown products. The source of the ground water contaminants was found to be a former water treatment system drain field.  CL-Out® bioremediation was implemented to reduce the volume of contamination in the source area and down gradient. CL-Out® is a consortium of Pseudomonas sp. that produces constitutive enzymes to cometabolize PCE and other halogenated solvents.  Dextrose is added with CL-Out® to provide a substrate for microbial growth.  Application of CL-Out® bioremediation at this site reduced the total chlorinated solvent concentrations as much as 99% in less than 6 months.

Geology and Hydrogeology

The site is located in Tampa, Florida where the geology is characteristically interbedded silt and sand.  The background ground water redox conditions of the aquifer are not known.


The PCE and elevated concentrations of daughter products were found in ground water down gradient of the former drain field.  The PCE concentrations were as high as 280 µg/L and DCE concentrations were as high as 4,400 µg/L, which indicates that there was significant contaminant degradation occurring, but the natural degradation stalled at DCE.   Petroleum hydrocarbons were also present in the ground water and may have served as an oxygen sink during the degradation of the petroleum products.

Remediation Design

CL-Out bioremediation was implemented in the ground water to accelerate the remediation of the source area.  A 55-gallon slurry of  CL-Out was injected on February 11, 2003.

Monitoring wells in the source area and surrounding area were sampled to assess the progress of the remediation.   The following table shows the pre-treatment and post-treatment CVOC concentrations in a source area monitoring well (MW-1) near the application of CL-Out.

 Source Area (MW-1)

Sampling Date CVOC Concentrations (µg/L)
3/28/02 280 750 4,400 BDL
12/19/02 86 120 1,100 BDL
2/11/03 CL-Out Injection
2/24/03 350 280 1,600 BDL
7/7/03 4.6 6.0 63 BDL


After application CL-Out bioaugmentation the chlorinated solvent concentrations in MW-1 decreased by as much as 99%.  Overall the total mass of contamination was significantly diminished by the bioaugmentation in a short period of time to accelerate the natural degradation.

PAH Bioremediation

The results of a recent bench-scale test confirmed the effectiveness of a special blend of CL Solutions’ microbes formulated for PAH bioremediation.  The test results showed that after two weeks, the total concentration of 15 PAH compounds decreased by 85% from a total of 358 mg/kg to 50.9 mg/kg.  Benzo(A)pyrene is often a most difficult PAH to remove. The test showed that the custom blend reduced the benzo(A)pyrene concentration from 24.5 mg/kg to 3.68 mg/kg.  Tests will continue to determine whether even greater effectiveness can be achieved over 30 days.