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.






BTEX and Naphthalene Bioremediation to BDL by Petrox Microbes

Case Study:
Orange County Fire and Rescue Station 81, Orlando, Florida

Oculus Number 8520434

Petrox was used to treat the residual petroleum contamination in ground water after the leaking tank was removed.  The petroleum contamination exceeded applicable standards for benzene, toluene, ethylbenzene, and xylene (BTEX) and naphthalene.  Petrox was injected into the ground water through 28 injection points covering a plume area of approximately 6,300 square feet.   Petrox injections were completed on June 18, September 11, and November 1, 2002.

Prior to bioaugmentation 100 pounds of ORC was added to provide supplemental oxygen for the bioremediation.  After verifying the dissolved oxygen concentration was more than 1.0 mg/l, the site was ready for bioaugmentation.

During the first injection 10 drums of Petrox were injected to cover the full plume.  As the area of contamination decreased, less Petrox was injected.  Five drums were injected in a focused application on September 11 and November 1, 2002.

Quarterly monitoring was completed during and after the inoculation to determine the bioremediation results.  The cleanup goals were achieved in the source area after the first inoculation.  The contamination persisted, however, in the down gradient wells.  The cleanup goals were achieved in the down gradient monitoring well after the third injection, but there was subsequent rebound.  After full distribution of Petrox was reached throughout the plume, the BTEX and naphthalene concentration were below detection limits (BDL), and cleanup goals were achieved and maintained. 

Please refer to the table below for the ground water monitoring results.

Monitoring Well Date Benzene Toluene Ethylbenzene Total Xylenes Naphthalene
MW-7 Source Area 6/12/2000 5.0 46.0 18.0 90.0 24.0
6/13/2001 39.0 272.0 167.0 526.0 26.0
3/14/2002 21.0 19.0 102.0 266.0 39.0
6/5/2002 ORC Added
6/18/02 10 Drums of Petrox Added
7/14/2002 <1.0 <1.0 <1.0 <2.0 <1.0
9/11/2002 <1.0 <1.0 <1.0 <2.0 <1.0
9/11/02 5 Drums of Petrox Added
10/7/2002 <1.0 <1.0 <1.0 <2.0 <1.0
11/1/02 5 Drums of Petrox Added
12/2/2002 <1.0 <1.0 <1.0 <2.0 <1.0
1/9/2003 <1.0 <1.0 <1.0 <3.0 <5.0
4/17/2003 <1.0 <1.0 <1.0 <2.0 <1.0

Down Gradient

6/12/2000 2.0 72.0 21.0 109.0 39.0
6/13/2001 14.8 677.0 207.0 1292.0 113.0
3/14/2002 71.0 1198.0 357.0 2408.0 193.0
6/5/2002 ORC Added
6/18/02 10 Drums of Petrox Added
7/15/2002 19.0 515.0 170.0 690.0 39.0
9/11/2002 <1.0 3.7 3.8 16.4 <1.0
9/11/02 5 Drums of Petrox Added
10/7/2002 6.4 2.3 4.7 23.8 15.0
11/1/02 5 Drums of Petrox Added
12/2/2002 38.0 515.0 95.0 460.0 10.0
1/9/2003 <1.0 <1.0 <1.0 <3.0 <5.0
4/17/2003 <110.0 1060.0 285.0 1120.0 65.0
4/29/2004 <1.0 <1.0 <1.0 <1.0 <1.0
9/1/2004 <1.0 <1.0 <1.0 <1.0 <1.0
12/1/2004 <1.0 <1.0 <1.0 <1.0 <1.0
3/21/2004 <1.0 <1.0 <1.0 <1.0 <1.0

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.

In-Situ Petroleum Bioremediation Rates With Petrox

Recent data from field applications of Petrox bioremediation show degradation rates of 100 to 500 micrograms per liter (ug/ml) per day. These degradation rates are for total petroleum hydrocarbons or total BTEX, depending on the site monitoring requirements.

Achieving high degradation rates requires high initial concentrations. Initial concentrations of 1,000 to 10,000 ug/l were used to develop these degradation rates.

At lower concentrations, the degradation rates depend on effective distribution of microbes for cell to contaminant contact. Secondly, desorption of petroleum constituents from submerged soil may cause rebound and suggest lower degradation rates. For these reasons we cannot calculate a degradation rate for petroleum at low concentrations.

In situ Heavy Oil Bioremediation in Alberta

Using a special microbial blend, Delta Environmental has been successfully bioremediating high concentrations of heavy oil in soil around pipelines and oil production equipment.  At a typical site, Delta reduced the concentration of petroleum C34 to >C50 from 130,000 mg/Kg to less than 10,900 in 30 days.  That is a removal rate of 3,970 mg/Kg/day.  This approach not only benefits the environment and meets green cleanup standards, but saves money and equipment downtime for the facility.