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Partitioning behaviour of sulfonamide, fluoroquinolone and macrolide antimicrobials in wastewater treatment

Behavior and fate of antimicrobials in wastewater treatment is determined by a complex interplay of different biochemical and physico-chemical processes, which involve both dissolved and particulate phase. Nevertheless, most of the literature reports focus on the microbial removal processes from the dissolved phase, while data on the possible role of partitioning processes are relatively scarce. In order to evaluate the relative importance of physico-chemical partitioning for different antimicrobial classes during wastewater treatment, an integrated method for the determination of both dissolved and particulate sulfonamide, fluoroquinolone and macrolide antimicrobials in wastewater treatment was developed. The dissolved antimicrobials were enriched by solid-phase extraction on hydrophilic- lipophilic balance (HLB) cartridges, while for the particulate fraction two different extraction techniques were evaluated: ultrasonication and accelerated solvent extraction. After the enrichment step, the extracts of the particulate fraction were additionally purified using the same SPE procedure as for the dissolved fraction. Several surrogate standards were added prior to the extraction step, to compensate any analyte loss during extraction and extract clean-up. The final extracts were analyzed by reversed-phase liquid chromatography coupled to electrospray ionization tandem mass spectrometry (ESI-MS/MS) in multiple reaction monitoring (MRM) mode with positive ionization. The method was applied for the analysis of real municipal wastewater samples as well as for the model samples from the pilot membrane biological reactor. Typical concentrations of analyzed antimicrobials in raw wastewater samples were in the range from 100 – 5000 ng/L and their removal in WWTP was found to be incomplete. The relative importance of physico- chemical partioning decreased in the following order: fluoroquinolones > macrolides > sulfonamides.

antimicrobials; wastewater; partitioning; LC/MS/MS

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