A NOTE ON BENZOTRIAZOLE CONCENTRATIONS IN THE RECEIVING WATERS OF DIFFERENT SEWAGE TREATMENT PLANTS

The concentrations of Benzotriazole (BTri), 4- and 5-methyl-benzotriazole (4-TTri, 5-TTri) were analyzed in the receiving river of a membrane bioreactor (MBR-MH), a conventional activated sludge (CAS-E) and a two-stage conventional activated sludge (CAS-M) sewage treatment plant (STP). All STPs were point sources for benzotriazoles in the aquatic environment as concentrations downstream the STPs were higher. Mean downstream concentrations

ranged from 3.58 µg L -1 (MBR-MH) to 1.1 µg L -1 (CAS- M) and 0.64 µg L -1 (CAS-E). CAS-E only slightly increased

downstream concentrations as the receiving river was already contaminated with up to 0.49 µg L -1 benzotriazoles from hydropower. 5-TTri was detected in lowest concentrations due to its good biodegradation, followed by BTri and 4-TTri. The latter two showed a potential to accumulate in the aquatic environment as they are only poorly biodegraded. Although the STPs were a point source for BTs into the aquatic environment, their impact strongly depended on the upstream water quality and the self-purification potential of the receiving river system..