Abstract

Each year more than 1.3 million metric tonnes of oil are released into the seas from manmade and natural sources. While mechanical and chemical processes have proven to have limited effectiveness, in many cases biological techniques are promising alternatives because of the lower costs, environmental friendliness associated with them. This study focuses on assessing the effectiveness of a rhamnolipid biosurfactant (JBR 425(TM)) and two other commercial biological products on biodegradation of weathered light crude oil, heavy crude oil, and diesel fuel spilled on saline water following the USEPA's biological effectiveness test method. The two products contain bacterial consortia and nutrients and were used as supplementary additives to enhance the biodegradation rate and extent of hydrocarbon compounds. Results show that at 20°C and 35 [per thousand] salinity, the mixture of rhamnolipid biosurfactant and one of the biological products overall produced the highest percentage of biodegradation at 81% for diesel fuel, 76% for light crude oil, and 64% for heavy crude oil after 28 days of experiment. Degradation rates of oil types for most of the treatments were in the order of diesel fuel > light crude oil > heavy crude oil and generally removal percentage and microbial densities had a direct relationship. The results obtained from this study show the potential for petroleum hydrocarbon removal enhancement in various oils by the addition of biological agents to the rhamnolipid biosurfactant