On-Site Bioremediation of Diesel-Contaminated Soil
Abstract
Mount Gambier is a medium sized rural city located in South Australia, approximately 450km south of Adelaide. Australian National (Railways) formerly operated a large site in the city. Site operations included the regular fuelling of locomotives with diesel fuel which led to contamination of the fuelling area due to spillage. Sinclair Knight Merz was engaged as part of a Commonwealth Government Assessment and Remediation program to remediate the site. Flinders University were engaged by Sinclair Knight Merz to contribute to the research and design of the Mount Gambier remediation program.
A series of soil analyses and laboratory tests on materials from the site were first undertaken to assess the potential for conducting in situ remediation using soil bioventing and to test the requirement for nutrient supplementation for either in situ or ex situ bioremediation. Assessment of the bioremediation potential in the laboratory tests as based on conducting tests with site soils supplemented with aeration and/or nutrient addition. The effects of supplements on rates of removal of hydrocarbons, numbers of soil bacteria and microbial activity using a rapid enzyme activity test were assessed. These tests indicated that aeration alone would not achieve significant reductions in levels of total petroleum hydrocarbons or stimulation of microbial activity and that nutrient supplementation was necessary. A series of biopile feasibility tests were then undertaken to determine remediation end points and the most effective nutrient supplementation using an ex situ biopile process.
Approximately 8000m3 of clean soil was excavated at the site in order to remove 2000 m3 of hydrocarbon contaminated soil. The validated clean fill was returned to the excavation and the contaminated soil was placed on the base of a designed biopile system. The full scale biopile process was commissioned in February 1999 and reductions in TPH from initial levels of approximately 15,000 mg.kg-1 to below 2,000 mg.kg-1 were achieved within 5 months. The remediation target is 1,000 mg.kg-1 and the projected remediation time frame is 12 months.