• Cetirizine can be metabolised by biofilm- but not by sludge wastewater reactors • Cetirizine metabolization results in eight well described metabolites • Cetirizine is ubiquitous in WWTPs all over the Baltic Sea • Cetirizine concentrations in wastewater are so high (1-8 µg/L) that they exceed PNEC Cetirizine was detected with concentrations ranging from 1-12 µg/L in effluent wastewater. No significant removal of cetirizine was observed in a full scale conventional activated sludge (CAS) wastewater treatment plant (WWTP) in a balancing experiment. In a larger sampling campaign involving 80 WWTPs across eight EU countries, cetirizine was detected and quantified in all WWTPs. All WWTPs discharged cetirizine concentrations exceeding its predicted no-effect concentration (PNEC). Even though removal of cetirizine in activated sludge treatment plants was not observed, biotransformation of cetirizine in a biofilm reactor was detected, pointing towards biodegradation in biofilms. Eight metabolites formed by the biofilm were characterised by high performance liquid chromatography followed by high resolution tandem mass spectrometry (HPLC-HRMS/MS) and possible structures of these microbial metabolites were described. The formation of cetirizine N -oxide in the biofilm reactor, was verified with authentic standards, and was found to be the main metabolite of microbial biotransformation. This compound was before known only from human metabolism. Other identified biotransformation reactions included hydroxylation, ether cleavage, dehydrogenation, and oxidation, giving thus access to future investigations in alternative wastewater treatment processes and in the environment. In spite of several metabolites being formed in biofilm systems at high Ceterizine concentrations, no metabolites including cetirizine N -oxide were detected in effluent wastewater in any WWTP at concentrations exceeded the LOD (0.01 µg/L) in WWTPs operating without ozonation.
Zhong et al. (Sun,) studied this question.