Removals of some hydrophobic poly aromatic hydrocarbons (PAHs) and Daphnia magna acute toxicity in a petrochemical industry wastewater with ultrasound in Izmir-Turkey

Abstract

The effects of increasing sonication time (60–150 min), NaCl (1.5–18 g/L), CCl 4 (200–1000 mg/L), pH (2–10) and air as dissolved oxygen (DO = 2–12 mg/L) concentrations on the destruction of four polycyclic aromatic hydrocarbons (PAHs) in a real petrochemical industry wastewater in Izmir (Turkey) were investigated. The yields in more hydrophobic PAHs with high benzene rings [benzo[ a]pyrene (BaP) and benzo[ k]fluoranthene (BkF)] were as high as the less hydrophobic PAHs with lower benzene rings [acenaphthylene (ACL) and carbazole (CRB)] at 60 °C after 150 min sonication. The removals in all PAHs increased significantly as the NaCl concentrations were increased from 1.5 up to 8 g/L, respectively. Continuous sparging of 5 mg/L DO increased the yields to 98% in less hydrophobic PAHs while more hydrophobic ones are removed with low yields. The more hydrophobic BaP, BkF and less hydrophobic ACL and CRB PAHs were sono-degraded under acidic and alkaline conditions, respectively, with high yields. The sono-destruction efficiency of more hydrophobic PAHs (97%) was enhanced by 17% with 600 mg/L CCl 4 after 150 min of sonication while the yields of less hydrophobic PAHs remained around 82%. Sonication alone provided 80% PAH yields. OH was the main process for complete sono-degradation of the ACL and CRB PAHs while pyrolysis was the main process for complete degradation of BaP and BkF PAHs. The Daphnia magna acute toxicity was significantly reduced.