Pharmaceuticals and many of their metabolites are biologically active substances that
are used in human and veterinary medicine and subsequently reach the environment
through different pathways. Numerous studies have confirmed their presence in
wastewater, surface and subterranean water, thus we can be subject to their influence
indirectly through consuming drinking water. In the beginning of the 1990s, the increase in
consumption of pharmaceutical products led to the widespread study of their influence on
the environment.
In our work, we have studied the elimination of selected pharmaceuticals and their
metabolites in a pilot wastewater treatment plant under aerobic and anoxic conditions and
in the coupled anoxic-aerobic reactor system. By measuring various chemical parameters
(ammonia, nitrate, nitrite, orthophosphate, chemical and biochemical oxygen demand) we
have confirmed the processes of nitrification in aerobic conditions and denitrification in
anoxic conditions. The model substances used were the non-steroidal anti-inflammatory
drugs ibuprofen, naproxen, ketoprofen and diclofenac, the antiepileptic carbamazepine,
clofibric acid, the human metabolite of the lipid regulator clofibrate, the metabolites of
carbamazepine acridine and acridone, and 1-(2,6-dichlorophenyl)indolin-2-one, a
metabolite of diclofenac. The substantial yearly consumption of the pharmaceuticals
justified our selection. We have used solid phase extraction to isolate the compounds from
the water samples, adding the internal standards deuterated ibuprofen and 9-chloroacridine
(for pharmaceuticals and metabolites respectively) in the process. This was followed by
derivatization with N-methyl-N-(tert-butyldimethylsilyl)-2,2,2-trifluoroacetamide. We
have used gas chromatography coupled with a mass spectrometry detector to perform the
separation and analysis.
The extraction efficiency was above 76% for all studied compounds. The elimination
of ibuprofen, naproxen, ketoprofen and acridine in aerobic conditions was over 90%, while
other compounds were eliminated in a lesser degree. In anoxic conditions, only naproxen
(87%) and acridine (64%) were eliminated substantially, the elimination of all other
compounds was below 13%. The elimination of ibuprofen, naproxen and ketoprofen was
greater in the coupled system than in individual reactors to a statistically significant degree,
while we could not confirm the same for other compounds.
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