Improving Long-Term Bioremediation Results with Nutrients

Adding Nutrients Increases Long-Term Population and Bioremediation Results

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.

Contaminant
Untreated Concentrations (ug/Kg)
Post-treatment concentrations (ug/Kg)
4,4-DDD
390
250
4,4-DDE
380
220
Toxaphene
8,500
440

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)
Contaminant
Pile 1
Pile 2
Before
After
Before
After
4,4-DDD
310
170
14
nd ( <5)
4,4-DDE
810
300
8.7
nd  (<5)
Toxaphene
12,000
7,300
380
nd (<5)

Conclusions

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.

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.

Chromium-Contaminated Ground Water Bioremediation

A bench-scale study demonstrated the viability of bioremediation of chromium contaminated ground water. The key factor to successful bioremediation was the selection of chromium-tolerant microbes. Actual contaminated ground water samples for the test. The ground water contained total chromium of 280 mg/L, with 270 mg/L hexavalent chromium.

The original sample was split into four bottles, with one preserved as a standard. Three split samples were treated with different blends of microbes. All three of the treated samples showed a reduction in the total dissolved chromium and nearly complete conversion from hexavalent to trivalent chromium. The average total chromium concentration in the treated samples was 160 mg/L and the hexavalent chromium concentration was 0.017 mg/L in two of the three treated samples. The sediments were not isolated for testing due to the small volume of sediment in the sample bottles.

Vials Showing Chromium Bioremediation Results

The photograph shows the untreated chromium-contaminated water on the left. The three bottles to the right were treated with various microbial blends.