Abstract

Soils that are co-contaminated with petroleum hydrocarbons and metals account for 55% of all hazardous waste sites and are hard to decontaminate because of the different nature of the remedial treatment required. Biosurfactant-producing microorganisms are present in many environments and can be stimulated to produce them under favorable conditions. This dissertation investigates the effect of biosurfactant production by indigenous microorganisms of a co-contaminated soil. A soil that was heavily contaminated with petroleum hydrocarbons and metals was acquired from the Toronto Harbour area. Phase one of the study evaluated the extent of the biodegradation of organic pollutants as well as the feasibility of biosurfactant production by the produced microorganisms. Results show that by the end of the experiment (50 days) batches amended with nutrients produced biosurfactants up to 3 times their critical micelle concentration (CMC). The produced surfactants caused the concentration of TPH and metals in the filtrate to increase from 2 to 8% and from 2 to 4%, respectively. In the phase two of the experiments the production of biosurfactants was enhanced by 40% by limiting the inorganic source of nitrogen in the batches, following a short growth phase. The produced biosurfactants were able to wash 10% of TPH and 6% of the metal content of the soil. The results indicate that biosurfactants can be produced by the indigenous soil microorganisms using organic contaminants as the sole carbon source. Furthermore, the produced biosurfactants showed potential to enhance biodegradation of petroleum hydrocarbons as well as to improve flushing of the remaining soil pollutant from soil