Bioremediation Of Marine Oil Spills Research Articles

Bioremediation of marine oil spills

Bioremediation is a potentially important option for dealing with marine oil spills. Oildegrading microorganisms are indigenous to the world's oceans, but environmental constraints limit their activity and so a bioremediation strategy must be tailored to local conditions. While an oil slick is at sea, its biodegradation is likely to be surfacearea limited and can be stimulated by employing dispersants. However, if oil reaches a shoreline, alternative options are needed. The addition of fertilizer nutrients has been successful in stimulating oil biodegradation in oligotrophic conditions, and suggests opportunities for designing alternative strategies for other environments.

Field evaluations of marine oil spill bioremediation.

Bioremediation is defined as the act of adding or improving the availability of materials (e.g., nutrients, microorganisms, or oxygen) to contaminated environments to cause an acceleration of natural biodegradative processes. The results of field experiments and trials following actual spill incidents have been reviewed to evaluate the feasibility of this approach as a treatment for oil contamination in the marine environment. The ubiquity of oil-degrading microorganisms in the marine environment is well established, and research has demonstrated the capability of the indigenous microflora to degrade many components of petroleum shortly after exposure. Studies have identified numerous factors which affect the natural biodegradation rates of oil, such as the origin and concentration of oil, the availability of oil-degrading microorganisms, nutrient concentrations, oxygen levels, climatic conditions, and sediment characteristics. Bioremediation strategies based on the application of fertilizers have been shown to stimulate the biodegradation rates of oil in aerobic intertidal sediments such as sand and cobble. The ratio of oil loading to nitrogen concentration within the interstitial water has been identified to be the principal controlling factor influencing the success of this bioremediation strategy. However, the need for the seeding of natural environments with hydrocarbon-degrading bacteria has not been clearly demonstrated under natural environmental conditions. It is suggested that bioremediation should now take its place among the many techniques available for the treatment of oil spills, although there is still a clear need to set operational limits for its use. On the basis of the available evidence, we have proposed preliminary operational guidelines for bioremediation on shoreline environments.

Field evaluations of marine oil spill bioremediation.

Bioremediation is defined as the act of adding or improving the availability of materials (e.g., nutrients, microorganisms, or oxygen) to contaminated environments to cause an acceleration of natural biodegradative processes. The results of field experiments and trials following actual spill incidents have been reviewed to evaluate the feasibility of this approach as a treatment for oil contamination in the marine environment. The ubiquity of oil-degrading microorganisms in the marine environment is well established, and research has demonstrated the capability of the indigenous microflora to degrade many components of petroleum shortly after exposure. Studies have identified numerous factors which affect the natural biodegradation rates of oil, such as the origin and concentration of oil, the availability of oil-degrading microorganisms, nutrient concentrations, oxygen levels, climatic conditions, and sediment characteristics. Bioremediation strategies based on the application of fertilizers have been shown to stimulate the biodegradation rates of oil in aerobic intertidal sediments such as sand and cobble. The ratio of oil loading to nitrogen concentration within the interstitial water has been identified to be the principal controlling factor influencing the success of this bioremediation strategy. However, the need for the seeding of natural environments with hydrocarbon-degrading bacteria has not been clearly demonstrated under natural environmental conditions. It is suggested that bioremediation should now take its place among the many techniques available for the treatment of oil spills, although there is still a clear need to set operational limits for its use. On the basis of the available evidence, we have proposed preliminary operational guidelines for bioremediation on shoreline environments.

Bioremediation of petroleum pollutants

Hydrocarbon-degrading microorganisms are ubiquitously distributed in soil and aquatic environments. Populations of hydrocarbon-degraders normally constitute less than 1% of the total microbial communities, but when oil pollutants are present these hydrocarbon-degrading populations increase, typically to 10% of the community. With regard to rates of natural degradation, these typically have been found to be low and limited by environmental factors. Rates reported for pristine marine waters typically are less than 0·03 g/m 3/day. In adapted communities rates of hydrocarbon degradation of 0·5–50 g/m 3/day have been reported. Bioremediation tries to raise the rates of degradation found naturally to significantly higher rates. The two general approaches that have been tested for the bioremediation of marine oil spills are the application of fertilizer to enhance the abilities of the indigenous hydrocarbon-utilizing bacteria and the addition of naturally occurring adapted microbial hydrocarbon-degraders by seeding. Bioremediation, accomplished by the application of fertilizer to enhance the abilities of the indigenous hydrocarbon-utilizing bacteria, was successfully applied for the treatment of the 1989 Alaskan oil spill in Prince William Sound, Alaska. Seeding with adapted nonindigenous microbial hydrocarbon degraders was tested on smaller spills in Texas—such as the Mega Borg spill—but bioremediation to remove petroleum pollutants by seeding has yet to be demonstrated as efficacious in field trials. The spill of more than 200,000 barrels of crude oil from the oil tanker Exxon Valdez in Prince William Sound, Alaska, as well as smaller spills in Texas—such as the Mega Borg spill—have been treated by bioremediation to remove petroleum pollutants. The Exxon Valdez spill formed the basis for a major study on bioremediation through fertilizer application and the largest application of this emerging technology. Three types of nutrient supplementation were tested: water-soluble (23:2 N:P garden fertilizer formulation): slow-release (Customblen); and oleophilic (Inipol EAP 22). Each fertilizer was tested in laboratory simulations and in field demonstration plots to determine the efficacy of nutrient supplementation. The use of Inipol EAP22 (oleophilic microemulsion with urea as a nitrogen source, laureth phosphate as a phosphate source, and oleic acid as a carbon source) and Customblen (slow-release calcium phosphate, ammonium phosphate, and ammonium nitrate within a polymerized vegetable oil coating) was approved for shoreline treatment and was used as a major part of the cleanup effort. Multiple regression models showed that nitrogen applications were effective in stimulating the rates of biodegradation.