Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Chemical and Biochemical Engineering

Supervisor

Dr.Ajay K. Ray

Abstract

One of the limitations in treating highly absorbing fluids with ultraviolet photoreactors is the short light penetration into the fluid leading to the following issues: (a) if not engineered properly, ultraviolet photoreactors dealing with highly absorbing fluids are likely to be energy-inefficient due to a non-ideal use of emitted photons and non-uniform dose distribution (b) the quantification of photo-chemical rate constants could be a challenging task due to the severe mixing-limited conditions of the experimental apparatus used during the investigation. As a result, new lab-scale apparatus (alternative to the conventional collimated beam system) and modeling approaches are needed in order to overcome such technical limitations.

The aim of this thesis is two-fold: firstly, to develop and validate lab-scale apparatus and standard operating procedures suitable for investigating the disinfection and the advanced oxidation processes (AOPs) initiated by short-penetrating wavelengths; secondly, to apply such newly developed methodologies for quantifying microbial inactivation kinetics in liquid foods by 253.7 nm light as well as total organic carbon (TOC) removal from ultrapure water by Vacuum-UV-initiated (VUV) AOPs employing the 172 and the 185 nm wavelengths.

For quantifying microbial inactivation kinetics in liquid foods, a Taylor-Couette (TC) apparatus can be used for fluids with ultraviolet transmittance as low as ~0.001% cm-1. A computational fluid dynamics (CFD) model was used to optimize the TC system, indicating that a Taylor number of ~46,500 was sufficient to overcome the very short UV light penetration.

For the TOC removal from ultrapure water by AOPs employing VUV light a mechanistic VUV-AOP model was developed by incorporating the vacuum UV-AOP kinetics into the theoretical framework of in-series continuous stirred tank reactors (CSTRs). Experimental trials were conducted using an annular photoreactor equipped with VUV lamps able to emit the 185 nm and 172 nm radiation revealed that, at the investigated conditions, the 185 nm AOP process gave three times better TOC degradation performance than the 172 nm AOP process.

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