Evolution of polycyclic aromatic hydrocarbons (PAHs) and heavy metals in sludge samples from conventional activated sludge wastewater treatment plants

摘要

This paper presents results on the presence and evolution of PAHs and heavy metals in a conventional activated sludge wastewater treatment plant (WWTP). The 16 PAHs recommended by the EPA were determined. On the other hand, 13 heavy metals were studied (Al, Cd, Co, Cr, Cu, Fe, Hg, Mn, Mo, Ni, Pb, Ti and Zn). Moreover, water content, organic and mineral matter were determined for the generic characterization of the sludges in an attempt to assess their agricultural value. The sewage sludges originated from the Guadalete WWTP site in Jerez de la Frontera (Cadiz, Spain). PAHs have been extracted by microwave energy. High performance liquid chromatog-raphy coupled with diode array and fluorescence detectors have been used (HPLC-DAD-FL). Heavy metals were analyzed by ICP-AES. The results showed that total PAHs concentration (sum of 16 EPA PAHs) varied between 6757 ng g~(-1) dry matter (DM) for compost and 4176 ng g~(-1) DM for secondary sludge. The most abundant PAH is pyrene. The highest concentration of heavy metals was also found in compost (51750mg kg~(-1) DM) and lowest concentration in secondary sludge (24250 mg kg~(-1)). In order to obtain global conclusions from all results, several chemometrical techniques of pattern recognition were applied.