Vanessa J. Pereira presented her final oral defense

Analytical Methods Validation and Bench Scale UV Treatment of Pharmaceutical and Contrast Media Compounds in Surface Water
Due to the high use of pharmaceuticals and contrast media in many industrialized countries, these compounds are expected to occur ubiquitously in the aquatic environment including sewage, surface, ground, and drinking water. The pharmaceutical compounds selected in this study belong to different therapeutic classes (analgesics, antibiotics, antiepileptics, blood lipid regulators, and contrast media agents) and are known to occur in the aquatic environment.

Analytical methods were validated to monitor the occurrence of these compounds in surface water. Specifically, the use of three derivatizing agents (diazomethane, MTBSTFA, and BSTFA) were compared for the analysis of acidic compounds such as ibuprofen, diclofenac, naproxen, and clofibric acid by gas chromatography mass spectrometry, and a simple one step solid phase extraction method followed by liquid chromatography-electrospray tandem mass spectrometry is proposed for analysis of the highly used X-ray contrast media iohexol.

Direct and indirect photolysis of pharmaceutical compounds was also investigated in laboratory grade water and surface water using batch low and medium pressure ultraviolet reactors. Fundamental photolysis and advanced oxidation process parameters obtained in LGW (such as the decadic molar absorption coefficient, quantum yield, and degradation rate constants) are reported and discussed. These parameters, together with the incident photon irradiance, solution depth, and solution absorbance were used to develop direct and indirect photolysis models that were compared with experimental results obtained in the surface water. The model predicted the experimental direct photolysis removals very well but underestimated the low pressure indirect photolysis results obtained for naproxen and carbamazepine. These models were also used to discuss the effects of optical path length and hydrogen peroxide concentration in the direct and overall photolysis rate constant predictions. Even though these experiments were conducted in batch reactors, on a bench-scale, and therefore the irradiance measurement is less complex than in a full-scale UV reactor, these findings have implications for wastewater and drinking water treatment and show that a wide range of pharmaceutically active compounds can be degraded by the use of direct and indirect photolysis.

Advisor: Professor Howard S. Weinberg

Readers: Professor Karl G. Linden
Professor Philip C. Singer
Professor Michael T. Meyer
Professor Michael D. Aitken
Professor Mark D. Sobsey

For further information please contact Rebecca Riggsbee Lloyd by email at Rebecca_Lloyd@unc.edu