Polycyclic Aromatic Hydrocarbons (PAHs) Removal during Anaerobic and Aerobic Sludge Treatments

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are of particular interest because of their potential toxic and carcinogenic properties. Due to their low water solubility and their high affinity for organic matter, PAHs are easily concentrated in sewage sludge and may contribute to the contamination of agricultural soils by spreading. In this study, the behavior of 13 PAHs was assessed during anaerobic and aerobic mesophilic treatments of naturally PAH-contaminated sewage sludge. It was shown that abiotic losses were strictly limited to the light PAHs, e.g. fluorene, phenanthrene and anthracene. Under methanogenic conditions, PAH removal was about 50% whatever PAH molecular weight. More specifically, PAH removal was closely linked to solids reduction implying limitation by bioavailability. Under aerobic conditions, the aerated process enhanced PAH removal up to 90%. In contrast, the aerobic treatment is more efficient than the anaerobic treatment to remove PAHs from contaminated sludge by favoring the PAH diffusion. Moreover, the aerobic process was successful for sludge decontamination because outlet concentrations in dry weight were lower than actual French required values, for fluoranthene and benzo[b]fluoranthene.