Date of Award

Spring 1-1-2012

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Karl G. Linden

Second Advisor

Fernando Rosario-Ortiz

Abstract

Advanced oxidation processes (AOPs) are an effective treatment technology for a variety of organic pollutants. Hydroxyl radicals (HO•) are the main reactive species in the process. In this work, application of UV/H2O2 AOP for treatment of pharmaceuticals in wastewater was studied. Two aspects of the process were investigated: (1) the properties of the transformation products of the pharmaceutical pollutants, and (2) the effects of the background water matrix on the efficiency of the process.

Because AOP does not completely remove the parent molecule but rather transforms it into a product, it is important to understand whether the product retains the environmentally relevant properties of the parent molecule. This study evaluates the biodegradability of the products of biologically recalcitrant pharmaceuticals as well as changes in antibacterial activity of antibiotics, as they get transformed by AOP. Mass spectrometry, liquid scintillation counting and biological assays were used to quantify the effect of AOP on the properties of the transformation products.

Many background water matrix constituents in effluents are highly reactive with HO• and decrease the efficiency of the process. Effluent dissolved organic matter (EfOM) in particular is one of the major sinks of HO• in the urban water cycle. Because of the non-homogeneous nature of EfOM, its reactivity with HO• is variable and makes the process modeling more difficult. A statistical model was developed in this work to analyze correlations between the reactivity of EfOM with HO• and the bulk properties of EfOM, water quality parameters, treatment train characteristics, and fluorescence derived data. The statistical analysis identified a set of dominant predictors for the reactivity between EfOM and HO•. In addition to HO• scavenging compounds, there are also background constituents that can generate HO•. Nitrate in particular is a common constituent in effluents known to generate HO• when exposed to UV. The efficiency of using nitrate rather than hydrogen peroxide for generation of HO• when using UV sources emitting in the 200-240 nm wavelength range was evaluated, and a model was devised to predict the outcome of the process.

Overall, the results of this work advance the fundamental scientific understanding of UV/H2O2 AOP and will help to guide engineering decisions in its applications to wastewater for the treatment of emerging contaminants.

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