Removal of clofibric acid and diclofenac during anaerobic digestion of sewage sludge

Removal of two acidic pharmaceuticals, clofibric acid and diclofenac, present in sewage sludge using two kinds of anaerobic digestions was investigated. The effective isolation and purification pretreatment to extract the target compounds from the sewage sludge samples was firstly established, followed by gas chromatography-mass spectrometry (GC-MS) analysis to identify and quantify them. Under mesophilic conditions, the removal efficiencies for clofibric acid and diclofenac with the initial concentrations of 5 μg /dm3 were up to 95% and 97%. After thermophilic anaerobic digestion, the removal efficiency could be increased to 99.3% for clofibric acid, however, it did not increase for diclofenac. In general, anaerobic digestion could effectively remove the target compounds from the sewage sludge (all above 90%).