Persistent Organic Pollutants in Sewage Sludge: Occurrence, Temporal Concentration Variation and Risk Assessment for Sewage Sludge Amended Soils

In this study, the occurrences, temporal concentration variations and ecotoxicological risks were determined for 18 polycyclic aromatic hydrocarbons (PAHs); 7 congeners of polychlorinated biphenyls (PCBs), and 18 selected organochlorine pesticides (OCPs) in the anaerobically digested sewage sludge samples obtained from a conventional wastewater treatment plant (WWTP) in Konya, Turkey. Flowrate of the evaluated WWTP was 200,000 m(3)/day, with the production of 140 tons/day treated sewage sludge. Total 18 PAHs were in the range of 1,203 - 17,599 & mu;g/kg of dry matter (dm); total PCBs were in the range of 51.26 - 561.37 & mu;g/kg dm, and total OCPs were in the range of 4.90 - 13.11 & mu;g/kg dm. The highest concentrations were determined for fluoranthene among PAHs, with 2445 & mu;g/kg dm, PCB118 congener with 514 & mu;g/kg dm, and & delta;-HCH among OCPs with 2.44 & mu;g/kg dm. Considering the average daily production amounts of treated sludge, the highest mass loads were 1,785 g/day for total PAHs; 79 g/day for total PCBs; and 1 - 2 g/day for total OCPs, while the annual mass load was estimated to be approximately 7.3 kg. An ecotoxicological risk assessment was performed by estimation of risk quotients (RQs). High risk for soil ecosystem was identified due to PAHs and PCBs ingredient of sludge, while lower risk was determined for OCPs compounds. The highest RQ values were determined for pyrene (RQ: 1337) among PAHs, PCB118 congener (RQ: 7608), and & gamma;-HCH (RQ: 5.23) among OCPs. Findings of this study show that sewage sludge can be an important source in the spread of persistent pollutants to the environment, and may pose a risk for soil ecosystem.