The occurrence and treatment of antibiotics in a micro-polluted lake which serves as a drinking water source in East China was surveyed. A pilot plant with conventional and O3-BAC (biological activated carbon) processes was set up to investigate its effectiveness in dealing with the contaminants. Solid phase extraction (SPE) coupled with electro-spray ionization-tandem mass spectrometry (LC-ESI-MS-MS) was applied to detect various antibiotics simultaneously. Three groups of antibiotics, i.e. sulfonamides, fluoroquinolones and tetracyclines, were detected in the source water. The gross concentrations of them in the lake are up to 471, 23.4 and 1,039 ng/L, respectively. The conventional and O3-BAC processes could remove 78.9, 62.4 and 70.2% of them, respectively. Among the antibiotics, tetracyclines could be effectively removed by ozonation, while fluoroquinolones could be removed by the coagulation–sedimentation process. BAC could not degrade fluoroquinolones but enabled the reduction of the other two antibiotics. In addition, O3-BAC was an effective technology for the removal of bulk organic matter. The concentrations of chemical oxygen demand (CODMn), UV254 and dissolved organic carbon (DOC) in the effluent of the up-flow BAC process were 2.31 mg/L, 0.034 cm−1 and 1.76 mg/L, respectively, with the corresponding removal rates of 45.1, 67.3 and 65.1%, respectively. In all, the combined conventional and O3-BAC process was the best available technology to remove organic matter as well as antibiotics.