Thursday, October 14, 2010

Degrading Crude Oil Contaminants in Soil Using Bioremediation

As a society, we rely on oil as a huge source of energy, but when that oil gets into the soil it can have very negative effects. Crude oil is a fossil fuel made up of a mixture of hydrocarbons found beneath the earth’s surface. When refined, it can be turned into many different things including gasoline. However during the drilling and refining process, some crude oil leaks and contaminates the soil. This is a problem because of the environmental effects of the soil contamination.

A study was recently done by Yaohui Xu and Mang Lu on the bioremediation of soil that is contaminated with crude oil, looking for efficient ways to reduce the soil contamination.

Bioremediation is a way of cleaning the soil and getting rid of the oil. It is also an efficient and low cost way of achieving results. The 2010 study “Bioremediation of crude oil-contaminated soil: Comparison of different biostimulation and bioaugmentation treatments” compares the efficiency of two different methods of bioremediation: biostimulation and bioaugmentation (Xu and Lu 2010).

In the study, samples of soil were collected from a crude oil spill site in China. The samples were either bioaugmented with bacteria which use hydrocarbons or biostimulated with an inorganic fertilizer for 12 weeks. Peanut hull powder was used as a bulking agent and carrier to immobilize the bacteria and improve oxygen flow. It was used because it inexpensive, biodegradable and easily available. It also has a low density, can hold a lot of water and conditions soil.  The degradation of the oil contaminants was measured using gas chromatography-mass spectrometry (Xu and Lu 2010).
Changes in concentrations of petroleum fraction during bioremediation. (a) TPH; (b) the polar fraction. Treatment A: soil; treatment B: soil+bacteria solution; treatment C: nutrient+peanut hull powder; treatment D: nutrient+peanut hull powder+immobilized cells. Values in each column labelled with an asterisk (*) indicated significant (p<0.05) differences between treatment A and other treatments at week 12. (Xu and Lu 2010)

The results of the study showed that the treatments of just soil with biostimulation and soil with a bacteria solution with biostimulation were not very effective, with 26% and 27% efficiencies respectively. Adding bacteria which had been immobilized on peanut hull powder (bioaugmentation) was the most effective at degrading the oil contaminants in the soil, with a 61% total removal efficiency.  It was found that adding peanut hull powder had a significant effect of degradation of hydrocarbons (38% efficiency).  The authors of the study suggest that the reason biostimulation was not effect compared to bioaugmentation might be because the limiting factor in degrading the oil could be either nutrition or aeration, both of which the peanut hull powder provides. Using this bulking agent increased oxygen diffusion, flow of water and nutrients, all of which are necessary for biodegradation of hydrocarbons found in crude oil (Xu and Lu 2010).

The study concluded that the most effective method of bioremediation was using bioaugmentation with bacteria immobilized on a biocarrier such as peanut hull powder (Xu and Lu 2010). Though these results were only for laboratory conditions, this method has potential to be used on a larger scale.  There is a lot of soil that has been contaminated by crude oil and biodegradation could be a good and safe way to clean the soil up.


Xu, Yaohui and Lu, Mang.2010.  “Bioremediation of crude oil-contaminated soil: Comparison of different biostimulation and bioaugmentation treatments.” Journal of Hazardous Materials, 183: 395-401.

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