Degradation
of Antibiotic Activity during UV/H<sub>2</sub>O<sub>2</sub> Advanced
Oxidation and Photolysis in Wastewater
Effluent
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Abstract
Trace
levels of antibiotics in treated wastewater effluents may
present a human health risk due to the rise of antibacterial activity
in the downstream environments. Advanced oxidation has a potential
to become an effective treatment technology for transforming trace
antibiotics in wastewater effluents, but residual or newly generated
antibacterial properties of transformation products are a concern.
This study demonstrates the effect of UV photolysis and UV/H<sub>2</sub>O<sub>2</sub> advanced oxidation on transformation of 6 antibiotics,
each a representative of a different structural class, in pure water
and in two different effluents and reports new or confirmatory photolysis
quantum yields and hydroxyl radical rate constants. The decay of the
parent compound was monitored with HPLC/ITMS, and the corresponding
changes in antibacterial activity were measured using bacterial inhibition
assays. No antibacterially active products were observed following
treatment for four of the six antibiotics (clindamycin, ciprofloxacin,
penicillin-G, and trimethoprim). The remaining two antibiotics (erythromycin
and doxycycline) showed some intermediates with antibacterial activity
at low treatment doses. The antibacterially active products lost activity
as the UV dose increased past 500 mJ/cm<sup>2</sup>. Active products
were observed only in wastewater effluents and not in pure water,
suggesting that complex secondary reactions controlled by the composition
of the matrix were responsible for their formation. This outcome emphasizes
the importance of bench-scale experiments in realistic water matrices.
Most importantly, the results indicate that photosensitized processes
during high dose wastewater disinfection may be creating antibacterially
active transformation products from some common antibiotics