Bioremediation of PAH-contaminated soil by composting: a case study

Composting technique was used for bioremediation of industrial soil originating from a former tar-contaminated site. The composting process was regulated by aeration to keep optimal temperature gradient and concentrations of O2 and CO2 inside the composting pile. The efficiency of bioremediation was evaluated by performing analysis of 11 individual three- to six-ring unsubstituted aromatic hydrocarbons (PAH) and estimating of changes in ecotoxicity of the contaminated soil. After 42 d of composting, PAH with 3-4 rings were removed from 42 to 68%, other higher-molar mass PAH from 35 to 57%. Additional 100 d of compost maturation in open-air field did not result in a further decrease of PAH. Ecotoxicity tests performed with bioluminescent bacteria Vibrio fischerii showed a decrease in toxicity both after composting and maturation phases. However, toxicity tests on mustard-seed germination did not reveal any significant changes during composting and maturation phases.