The occurrence of pharmaceuticals in the aquatic environment
is
a global water quality challenge for several reasons, such as deleterious
effects on ecological and human health, antibiotic resistance development,
and endocrine-disrupting effects on aquatic organisms. To optimize
their removal from the water cycle, understanding the processes during
biological wastewater treatment is crucial. Time-of-flight secondary
ion mass spectrometry imaging was successfully applied to investigate
and analyze the distribution of pharmaceuticals as well as endogenous
molecules in the complex biological matrix of biofilms for wastewater
treatment. Several compounds and their localization were identified
in the biofilm section, including citalopram, ketoconazole, ketoconazole
transformation products, and sertraline. The images revealed the pharmaceuticals
gathered in distinct sites of the biofilm matrix. While citalopram
penetrated the biofilm deeply, sertraline remained confined in its
outer layer. Both pharmaceuticals seemed to mainly colocalize with
phosphocholine lipids. Ketoconazole concentrated in small areas with
high signal intensity. The approach outlined here presents a powerful
strategy for visualizing the chemical composition of biofilms for
wastewater treatment and demonstrates its promising utility for elucidating
the mechanisms behind pharmaceutical and antimicrobial removal in
biological wastewater treatment.