Laboratory Assessment of Bioremediation Products Under Freshwater Conditions

The recovery and transportation of petroleum and petroleum products creates the potential for spillage of these materials into the environment. Bioremediation is a recently applied technology for clean up after a petroleum spill, and a protocol for evaluating bioremediation products in marine systems has been instituted. The U.S. Environmental Protection Agency (EPA) undertook this research to extend the protocol to freshwater systems, and to validate the protocol by examining commercial products for effectiveness in the laboratory. EPA's shake flask protocol developed for marine systems was adapted for this work. Commercial products were applied per manufacturer's recommended dosage. All flasks received weathered Alaska North Slope oil at 5 g/L. The test flasks contained the commercial products with an inoculum developed from freshwater sources unless the product contained microbes. The control was an oil degrading inoculum in Bushneil Haas (Difco) medium. Triplicate flasks for each treatment were sacrificed on days 0, 7, 14, 21, and 28. Most-Probable-Numbers of alkane and aromatic hydrocarbon degraders were measured. The microbiological populations degrading alkane and aromatic hydrocarbons increased up to four orders of magnitude for all products except one. The original inoculum contained approximately 103 cells/mL of alkane degraders and 104 cells/mL of aromatic degraders. Oil analysis over the experimental period revealed differences in oil degradation among the products. After 28 days alkane reduction was 98% for the Bushnell-Haas control and 94% for Product A. Aromatic reduction was 53% in the control and up to 66% for product A. Product B was similar in alkane reduction but less effective with aromatics. Product C was ineffective in reducing either class of compounds. Product D reduced alkanes 37% and aromatics 47%. Oxygen uptake and CO2 production were high for the control and Products A and B, but low for Products C and D. The protocol was able to demonstrate clear differences among products and thus was deemed successful for evaluating product performance.