Removal of Typical Pharmaceutically Active Compounds in Sewage Sludge Using Anaerobic Digestion Processes

The removal of four pharmaceutically active compounds (PhACs), i.e. anti-inflammatory painkiller diclofenac (DFC), lipid regulating agent clofibric acid (CFA), epilepsy drugs carbamazepine (CBM), and broad-spectrum antibacterial agent triclosan (TCS), present in sewage sludge was investigated using anaerobic digestion (AD) processes in the mesophilic and thermophilic mode. Sludge retention times (SRTs) were 10 d, 15 d, and 20 d for the mesophilic mode and 7 d, 15 d, and 20 d for the thermophilic mode. The effective isolation and purification pretreatment to extract the target compounds from the sewage sludge samples was firstly established, followed by gas chromatography-mass spectrometer (GC-MS) analysis to identify and quantify them. The removal efficiencies of the target compounds could be raised to a certain extent with the increase on SRTs, especially under the mesophilic condition. The removal of CFA and TCS under thermophilic condition hardly varied when the SRTs were above 15 d. All the compounds could be partly removed from the sewage sludge under the two temperature conditions, particularly the triclosan which was obtained about 74% of removal. Besides, CFA, firstly reported in this study, could obtained maximal 65% removal efficiency during ADs of sewage sludge. On the whole, the thermophilic mode was more conducive to the removal of CFA, CBM and TCS, but DFC could be better removed in the mesophilic mode.