Evaluation of landfarm remediation of hydrocarbon-contaminated soil at the Inveresk Railyard, Launceston, Australia

Costing of landfarm bioremediation of hydrocarbon-contaminated soil (2700 m3 material) at a disused railyard site in Tasmania, Australia is reported. The landfarm area (8000 m2) was enclosed in an impermeable clay embankment and where necessary the base was also rolled with clay. Microbial inoculation was not deemed to be necessary since suitable degrading biota were found to be present in site samples prior to commencement of the landfarming. Fertilizer amendment comprised primarily ammonium sulphate and superphosphate to give a C:N ratio (TPH:fertilizer) of 28:1 and a C:P ratio of 200:1. The soil was turned regularly and watered as required for the 12- month duration of the operation. Over this period levels of TPH showed a linear decline from a mean of 4644 mg/kg (SD = 1252 mg/kg) to near 100 mg/kg or less, with greatest losses being in the chain lengths C10-C28. The costing was determined to be $A13.40c per m3 ($A10.30c per tonne), which is at the lower end of the spectrum of reported landfarming costs. Costing of such operations is important since the reported economics will influence others' choice of bioremediation techniques.