Mass flows and removal of antibiotics in two municipal wastewater treatment plants

The mass flows and removal of 20 antibiotics of seven classes in two wastewater treatment plants (WWTPs) of Hong Kong were investigated in different seasons of a whole year, using bihourly 24 h flow proportional composite samples. Antibiotics were detected at concentrations of 3.2–1718, 1.3–1176 and 1.1–233 ng L−1 in influents, secondary and disinfection effluents. Total daily discharges of all the detected antibiotics from effluents of Shatin and Stanley WWTPs were 470–710 and 3.0–5.2 g d−1, respectively. Ampicillin, cefalexin, sulfamethoxazole, sulfadiazine, sulfamethazine, chlortetracycline and vancomycin were effectively (52–100%) eliminated by activated sludge process while ampicillin and cefalexin were effectively (91–99%) eliminated by disinfection. Bihourly variation analysis showed that concentrations of the major antibiotics in influents varied more significantly in Stanley WWTP which served small communities.

► Mass flows and elimination of 20 antibiotics in two WWTPs were investigated in 1 year.
► Seven and two antibiotics are effectively removed by AS and chlorination, respectively.
► Antibiotic consumption patterns vary significantly in different regions in the same city.
► Concentrations of antibiotics fluctuate significantly, as showed by the bihourly sampling.