Desorption of PAHs from solid phase into liquid phase during co-fermentation of municipal and coke sewage sludge

The work presents the results of the study that determined the changes in the concentration of polycyclic aromatic hydrocarbons (PAHs) in the sewage sludge and supernatants during the co-fermentation of municipal and coke sewage sludge. The municipal sewage sludge served as a control sample, and the mixture of municipal and coke sewage sludge was used as a test sample. The sewage sludge was incubated for 20 d at 37 degrees C in the dark. The quantification of the PAHs was carried out simultaneously in both the solid and supernatant phases, the latter separated from the sludge during centrifugation. After 20 d, the solid phase was observed to have its PAHs content reduced by 60% in the control sample and 64% in the analyzed one, respectively. The decline in the solid phase PAHs content was accompanied by a significant quantitative increase of the PAHs in the liquid phase, which proves the desorption of solid particles. The control supernatants showed the total concentration of 16 PAHs of 1.1 mu g/L prior to the treatment, and reaching 20.5 mu g/L after 20 d of incubation, while for the supernatants separated from the mixture of municipal and coke sewage sludge, a 13-fold higher total concentration of the analyzed PAHs was determined