Enhanced Biodegradation of Carbamazepine in Wastewater Effluent After UV/H2O2 Advanced Oxidation

Carbamazepine – an anti-epileptic drug – has been detected worldwide in waterways receiving municipal effluent. It passes virtually untransformed through all conventional wastewater treatment processes and through advanced processes such as membrane bioreactors. The advanced oxidation process (AOP) has been gaining interest as a technology that can transform and break down recalcitrant compounds such as carbamazepine. However, formation of unknown byproducts has always been one of the weak points of advanced oxidation.This study investigated the biodegradability of the UV-oxidation products of carbamazepine in municipal effluent. Secondary treated, pre-chlorinated wastewater effluent was spiked with C-14 labeled carbamazepine and was treated with UV/H2O2 AOP until the pharmaceutical was 90% degraded. The samples pre- and post-AOP treatment were inoculated with activated sludge bacteria. Each sample was connected to an alkaline trap to capture radiolabeled CO2 that formed during the mineralization of carbamazepine. The samples were analyzed with liquid scintillation counting and with liquid chromatography in combination with ion trap mass spectrometry or with a radiation detector.The results indicated that full mineralization of the compound did not occur during the AOP treatment applied. In addition, the non-AOP treated carbamazepine was completely nonbiodegradable. However, biodegradation of AOP pre-treated carbamazepine resulted in full mineralization of a significant fraction of the compound. A combination of the two processes – UV/H2O2 AOP and biodegradation - was able to achieve results that each process by itself could not. The results of this study suggest that coupling AOP with biofiltration at wastewater treatment facilities is a promising technology combination for addressing the treatment of pharmaceuticals in municipal effluent.