| The effect of surfactants on the enhancement of the biodegradation of petroleum-based compounds has been theoretically and experimentally investigated. One nonionic synthetic surfactant, (polyethoxyethanol) Igepal CA-630, and two nonionic biosurfactants (rhamnolipids) JBR-204, and JBR-425, were tested in the laboratory to show the effect on the biodegradation of motor oil and diesel fuel.; Igepal CA-630 was found to inhibit the biodegradation of motor oil. Both biosurfactants JBR-204 and JBR-425 were found to enhance the biodegradation of motor oil and diesel fuel to different degrees (up to 70%). However, the enhancement of biodegradation was found to occur during the increasing biodegradation phase.; The theoretical investigation showed that the surfactant has two possible roles in enhancing the biodegradation of petroleum-based compounds: one is to enhance the compound uptake by microorganisms (physical role), and another is to enhance the biochemical reactions inside the microorganisms (chemical role). It was found that the micelle size is a dominating parameter for the enhancement of compound uptake by microorganisms.; Based on the theoretical investigation, general hypotheses for the conditions of enhancement of biodegradation of petroleum-based compounds with surfactants were developed. The hypotheses were validated by the results of the experimental investigation of the current study and were also successfully applied to explain the results of the experimental work in other literature. The contradictory results of using surfactants in many other studies were clarified by the use of the current hypotheses. |
