Transformation of oxcarbazepine and human metabolites of carbamazepine and oxcarbazepine in wastewater treatment and sand filters.

Carbamazepine (CBZ) and oxcarbazepine (OXC) are widely used anticonvulsants that are extensively metabolized in the human body. The pharmaceuticals and their human metabolites are present in influents and effluents of wastewater treatment plants (WWTPs), in rivers and streams, and in drinking water. In this study, the biodegradation of OXC and its main human metabolite, 10-hydroxy-CBZ (10OHCBZ), and the main human metabolite of CBZ, 10,11-dihydro-10,11-dihydroxy-CBZ (DiOHCBZ), was investigated in contact with activated sludge from a wastewater treatment plant (WWTP) and sand filter material from a waterworks. The transformation of DiOHCBZ, 10OHCBZ, and OXC led to the formation of the following main TPs: 1-(2-benzoic acid)-(1H,3H)-quinazoline-2,4-dione (BaQD), 1-(2-benzoic acid)-(1H,3H)-quinazoline-2-one (BaQM), 9-aldehyde-acridine, 9-carboxylic acid-acridine (9-CA-ADIN), hydroxyl 9-CA-ADIN, acridone (ADON), 11-keto-OXC, and 2,2'-(carbamoylazanediyl)dibenzoic acid. TP formation could be explained by three proposed transformation pathways, including reactions such as oxidation, α-ketol rearrangement, or benzylic acid rearrangement. The results highlight the fact that the TP abundances strongly depend on the concentrations spiked in the lab-scale experiments. BaQD, 9-CA-ADIN, and ADON were detected in WWTP effluents, rivers, and streams. 9-CA-ADIN was found at maximum concentrations in WWTP effluent and rivers up to 920 ± 50 ng L(-1) and 304 ± 26 ng L(-1), respectively. Even in drinking water, BaQD and 9-CA-ADIN were present at concentrations of 26 ± 2 ng L(-1) and 189 ± 3 ng L(-1), respectively.