Field Study IX: Pilot-Scale Composting of PAH-Contaminated Materials: Two Different Approaches
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Results of this field study describe composting of two different PAH-contaminated materials (soils originated from four industrial sites and creosote-treated railway crossties). Sequential mild supercritical fluid extraction (SFE) was employed to estimate the fast-release fractions (F) of PAHs in order to predict bioaccessible portion of PAHs in the materials. These values were consequently compared with the real biodegradation data obtained from the two pilot-scale experiments in order to investigate whether the bioaccessible data can be used as a prediction parameter of the degradation efficiency. The final results of the PAH elimination ranged between 62.4% and 92.9% in the case of the soil samples and between 81.4% and 97.0% for two different treatments of contaminated railway crossties. The results showed that the elimination efficiency decreased with the increasing number of aromatic rings in the PAH molecules. Estimation of the bioaccessible fraction of PAHs using the SFE method has been proven to be a useful tool for prediction of the bioremediation process efficiency. This fact is particularly important because if the composting method is employed in the full scale, any addition of the necessary bulking agent leads to the final increase in the total amount of the treated hazardous wastes if the remediation process fails.
KeywordsComposting Bioremediation PAHs Supercritical fluid extraction Bioavailability
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