Enhancement with physicochemical and biological treatments in the removal of pharmaceutically active compounds during sewage sludge anaerobic digestion processes

The removal of 4 typical pharmaceutically active compounds (PhACs), i.e. clofibric acid (CFA), triclosan (TCS), carbamazepine (CBZ) and diclofenac (DCF) in sewage sludge was investigated during anaerobic digestions (ADs) under mesophilic and thermophilic conditions. The performances of ADs were enhanced with ultrasonic, mechanical rotary disc or enzymatic treatments. Ultrasonic pre-treatment could enhance the performances on the removal of PhACs better than ultrasonic post-treatment. CFA, TCS, CBZ, and DCF were finally reduced by 73%, 76%, 73%, and 64%, respectively, during thermophilic AD (TAD) combined with ultrasonic pre-treatment for 30 min at sound energy density 0.05 W/mL at SRT 15 d. For ADs combined with rotary disc pre-treatment or post-treatment, the removal of PhACs would be improved by less than 10%. Three selected enzymes, papain, cellulose and lysozyme showed different effects on the removal of PhACs during ADs. TCS could obtain the best removal, which was up to 82% and 81% in mesophilic AD (MAD) and TAD processes enhanced with lysozyme at SRT 15 d. On the whole, the increases on SRTs would improve the removal of PhACs during ADs and also the enhancement with enzymolyses.