(602w) Wastewater Treatment of Fluoroquinolone Antibiotics Using the UV-H2O2 Advanced Oxidation Process

Abstract by Sebastian Snowberger researching under Dr. Lee Blaney

With recent advancements in medicine, unprecedented amounts of pharmaceuticals are entering wastewater streams worldwide.  Current wastewater treatment plants do not specifically treat for pharmaceuticals; therefore, pharmaceuticals are not only discharged to the environment, but also reintroduced to drinking water supplies.  Health concerns of long-term ingestion of trace concentrations of pharmaceuticals through drinking water are widespread; however, toxicological studies are just beginning.  Regardless, numerous studies have identified ecological damage to aquatic wildlife due to pharmaceutical contamination.  To properly address these concerns, investigation of the abilities of advanced treatment processes to effectively remove pharmaceuticals from wastewater streams is merited.

This research examined the ability of the ultraviolet-hydrogen peroxide (UV-H₂O₂) advanced oxidation process to transform antibiotics into benign compounds.  Specifically, a batch-recycle UV reactor was employed to study the transformation of five fluoroquinolone antibiotics: ciprofloxacin, levofloxacin, norfloxacin, orbifloxacin, and sparfloxacin.  Transformation of fluoroquinolones was studied in DI water and also tertiary effluent from the Little Patuxent Water Reclamation Plant (Savage, MD).  The experimental solutions were prepared by adding pharmaceuticals (approximate concentrations of 2×10^-7 to 3×10^-9 M) and hydrogen peroxide (10^-5 to 10^-3 M) to the DI and wastewater solutions.  The pH in the DI solution was controlled using a 25mM phosphate buffer.  Experimental solutions were continuously pumped through the UV cell and samples were collected at specific time intervals.  Fluoroquinolone concentrations were measured using online solid-phase-extraction high performance liquid chromatography with fluorescence detection (oSPE-HPLC-FLD).  Transformation of fluoroquinolones occurred through direct photolysis and indirect photolytic mechanisms involving hydroxyl radicals, which were formed via hydrogen peroxide decomposition.  Reaction kinetics were investigated using para-chlorobenzoic acid (pCBA) as a hydroxyl radical probe compound (k^”_pCBA = 5.2×10⁹ M^-1s^-1).

The results of this research include determination of rate constants for transformation of the five fluoroquinolones with hydroxyl radicals (2–8×10⁹ M^-1s^-1), transformation of the five fluoroquinolones via direct and indirect photolytic mechanisms, the impact of the molar ratio of hydrogen peroxide to the total fluoroquinolone concentration, and the effect of background water quality (i.e., DI water vs. tertiary effluent) on the transformation of fluoroquinolones in the batch-recycle UV-H₂O₂ reactor.  Given the widespread adoption of UV technology for oxidation and disinfection purposes, the results of this research will prove useful to understanding treatment of antibiotics in advanced wastewater processes.