Liquid chromatography–(tandem) mass spectrometry for the follow-up of the elimination of persistent pharmaceuticals during wastewater treatment applying biological wastewater treatment and advanced oxidation

The persistent and hardly eliminable pharmaceutical compounds carbamazepine, diazepam, diclofenac and clofibric acid were monitored in municipal wastewater by electrospray LC–MS and LC–MS-MS in positive and negative mode under high resolution and high mass accuracy conditions. While biological treatment by conventional and membrane bioreactors failed, the advanced oxidation methods using ozone (O3), O3/UV or hydrogen peroxide in combination with UV (H2O2/UV) successfully led to the complete elimination of these compounds. Target compounds could be confirmed as permanently present pollutants in Aachen-Soers wastewater in concentrations between 0.006 and 1.9 μg l−1. Pharmaceuticals were determined after extraction using either C18 solid-phase extraction or by directly injecting them into the column without pre-concentration, achieving limits of quantification of 0.001 or 0.00001 μg l−1, respectively.