Fate of pharmaceutically active compounds in sewage sludge during anaerobic digestions integrated with enzymes and physicochemical treatments

Abstract

The removal of 4 typical pharmaceutically active compounds (PhACs) in sewage sludge, i.e. diclofenac (DCF), clofibric acid (CFA), carbamazepine (CBM), and triclosan (TCS), was evaluated during 3 integrated processes of anaerobic digestions (ADs). The integrated processes included ADs integrated with mixed enzymolyses (MEADs), ADs integrated with mixed enzymolyses together with ultrasonic irradiation pre-treatment (MEUADs), and ADs integrated with mixed enzymolyses together with mechanical rotary disc post-treatment (MEADRDs). The SRTs were set at 15 d. Gas chromatography-mass spectrometry (GC/MS) following solid-phase extraction was used to analyze and detect the target compounds. Under the mesophilic condition, the highest removal during MEAD and MEUAD was 67.6% and 77.1% of CFA, and 78.1% of CBZ during MEADRD. There was little differences between the removals of 4 PhACs during MEADRD, and all the removal rates were higher than 70%. Especially the removal of DCF increased from 40.6% during MEAD to 71.7% during MEADRD. The overall removal during MEADRD was highest with the increase by about 20.9% from that during MEAD. The highest removal during MEAD, MEUAD and MEADRD was 81.1%, 70.7% and 71.8%, respectively, of CFA under the thermophilic condition. MEADRD could realize the highest overall removal, up to 69.4% with the increase by 11.0% compared with MEUAD. The results showed that the integrated process, MEADRD, under both mesophilic and thermophilic condition was suitable for the effective removal of PhACs, and MEADRD under the mesophilic condition was a preferable choice from the energy-saving perspective.