Bioremediation of Petroleum Based Contaminants

The bioremediation of petroleum based contaminants involves the use of microorganisms to break down toxic chemicals in soil and water. These microorganisms consume contaminants as their energy source and eliminate them by changing their chemical composition into harmless gasses like carbon dioxide.

This process of remediation has many applications. Oil spills from petrol stations, industrial sites and farms are common sources of contamination. Contaminants like benzene and methyl tertiary butyl ether (MTBE) can be particularly dangerous because they are carcinogens.

1. Introduction

A naturally occurring process, bioremediation relies on microorganisms to break down or transform chemical pollutants into less harmful or non-toxic substances. This occurs as these organisms carry out their normal life functions, using the chemicals as energy sources. The susceptibility of the pollutant to degradation and the conversion into innocuous products is dependent on the chemical structure, solubility, temperature, soil conditions, and the presence of supplemental nutrients.

Petroleum pollutants are receptive to bioremediation, including crude oil, gasoline, fuel oils and diesel fuels. This process can be used to clean up contaminated sites such as petroleum stations and gas wells, industrial plants, landfills, and beaches.

The indigenous bacteria found in soil are able to degrade petroleum hydrocarbons, although the process can take years. To speed up this process, bulking agents such as straw, saw dust and bark can be added to a biopile. In addition, oxygen and supplemental nutrients such as inorganic nitrogen and phosphorous can be delivered to the soil through injection or diffusion wells. Non-indigenous butane-utilizing bacteria can also be introduced to the soil for enhanced bioremediation of petroleum contaminants.

2. Background

Petroleum hydrocarbons are the most widespread organic pollutants in soil. They have many harmful effects such as carcinogenicity, cytotoxicity, and eutrophication. They can also affect groundwater resources. They are the most common source of environmental pollution caused by human activities, requiring effective remediation.

Various types of microorganisms present in soil are capable of degrading these harmful contaminants by using them as carbon sources for growth. These bacteria produce enzymes that break down the petroleum hydrocarbons into smaller molecules, which are more water soluble. This process is known as bioremediation.

However, the rate of biodegradation of petroleum hydrocarbons is affected by many factors such as temperature, moisture, pH, redox potential, aeration and mineral nutrition. As a result, it takes a long time for the bacteria to degrade the petroleum hydrocarbons. To speed up the bioremediation of petroleum contaminated sites, we need to know more about these microbial reactions and how they are influenced by the environment. This will help us find ways to improve the natural degradation process. This will ultimately lead to more efficient and effective remediation of petrochemical contaminants.

3. Methods

There are several different methods for bioremediation of petroleum based contaminants. These include natural attenuation, bioaugmentation and biostimulation. Natural attenuation uses naturally occurring processes to transform or degrade pollutants into less harmful compounds or immobilize them in soil. Bioremediation can also be done by using plants that consume or otherwise remove the petroleum pollutant (landfarming and biopiles).

Microorganisms that are capable of breaking down petroleum hydrocarbons produce enzymes that help break the carbon-hydrocarbon bonds. These enzymes are important for biodegradation, and the rate of oil degradation depends on the number of microorganisms present, their metabolic capabilities, and the availability of energy.

During the 1970s, scientists began to investigate whether the addition of certain oxidants or nutrients could enhance microbial activity in petroleum hydrocarbon-contaminated ground water systems. While many of the technologies developed during this time met expectations set out by early investigators, others proved more difficult than expected. Some, such as air sparging and hydrogen peroxide addition, have been used successfully at many sites. Others, such as nitrate addition and bioslurping, have not. The varying responses of environmental factors to the bioremediation process make these methodologies difficult to predict.

4. Results

The bioremediation process can accelerate the elimination of petroleum hydrocarbon pollutants by transforming them into less toxic, water-soluble compounds. Microbial degradation processes are able to do this because microorganisms have enzyme systems that help break the hydrocarbons’ bonds. The biodegradation of petroleum hydrocarbons is a crucial process for the environment since it is a natural method to clean up organic pollutants that are difficult to remove using mechanical or chemical methods.

In this study, four blocks of soil were treated: a blank control (Ctrl), a block of untreated oily soil (BA), a blocked of oily soil that received bioaugmentation (BA+), and a block of oily soil that received biostimulation (BS). The BA+ and BS+ blocks were sprinkled with nutrients dissolved in deionized water. The BS+ and BA+ samples were then analyzed to determine if the addition of nutrients enhanced the activity of bacteria that could remove petroleum hydrocarbons.

All soil microorganisms require moisture for growth and function. However, too much moisture slows the rate of microorganism degradation because it reduces the amount of oxygen available for aerobic respiration.

5. Conclusions

Bioremediation is a natural process that relies on microorganisms to transform pollutants into harmless metabolites. Microorganisms use chemical contaminants as energy and food sources during the normal processes of cell growth. They degrade or change the harmful chemicals into water and harmless gases. It is less labor intensive than traditional methods, and is environmentally friendly because it does not require the use of hazardous chemicals.

The effectiveness of bioremediation is affected by the solubility, temperature, pH, and availability of nutrients for bacteria. The molecular structure of the pollutant also affects its bioremediation potential, and compounds with rigid molecular structures are more difficult to convert into innocuous substances. The amount of sunlight and the surrounding vegetation also affects bioremediation.

In situ bioremediation has been in use for over 20 years, and it is currently a commonly used method to remediate petroleum oil contamination. It involves a combination of techniques, including bioaugmentation (BA) and biostimulation (BS). These methods involve adding to the indigenous population of oil-degrading microorganisms or stimulating their growth by supplying them with the necessary substrates. These methods can be used in conjunction with floating booms to restrict the movement of water, thus allowing the microbial populations to be isolated and concentrated.