Occurrence and fate of phthalate esters in wastewater treatment plants in Qingdao, China

The concentrations of 16 phthalate esters (PAEs) were detected in the sewage and sludge from wastewater treatment plants (WWTPs) in Qingdao, China. The total PAE concentrations in the influent samples from the Chengyang, Licun River, and Haibo River WWTPs were 134.42, 186.02, and 135.72 ng/mL, respectively. Dimethyl phthalate (DMP), diethyl phthalate (DEP), dimethylglycol phthalate (DMGP), di(2-ethylhexyl) phthalate (DEHP), di(2-ethoxyethyl) phthalate (DEEP), dicyclohexyl phthalate (DCHP), and di-n-octyl phthalate (DnOP) were all detected, with DMP being the most abundant compound. By contrast, the total PAE concentrations in the effluent samples from the three WWTPs were 39.91, 55.42, and 44.37 ng/mL. The removal efficiencies for individual PAEs in the three WWTPs varied widely. DMP and DEP were removed effectively in the Chengyang WWTP, whereas DMP and DnOP were removed relatively well in the Chengyang and Haibo River WWTPs. In the sludge from the Chengyang, Licun River, and Haibo River WWTPs, the total PAE contents were 96.46 mg/kg, 91.20 mg/kg, and 98.45 mg/kg, respectively. According to the mass balance, most PAEs (48.30%-56.31%) in the sewage decreased, and 43.69%-51.70% of total PAEs were discharged to the environment through the effluent and sludge.