Thesis Defence: Evaluation of Water Matrix Effects on Light-Based Small Disinfection Systems

Faezeh Ketabchi, supervised by Dr. Nicolas Peleato, will defend their thesis titled “Evaluation of Water Matrix Effects on Light-Based Small Disinfection Systems” in partial fulfillment of the requirements for the degree of Master of Applied Science in Civil Engineering.

An abstract for Faezeh’s thesis is included below.

Examinations are open to all members of the campus community as well as the general public.

Please email nicolas.peleato@ubc.ca to receive the zoom link for this defence.

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ABSTRACT

The global challenge of providing clean water supply for an increasing population is growing at an unprecedented pace. The most acute public health risk associated with drinking water is the potential presence of pathogens due to ineffective treatment. Therefore, there is an essential need for effective and efficient drinking water disinfection systems. Ultraviolet (UV) radiation and photocatalytic technologies are effective light-based disinfection methods that have grown in popularity, particularly in resource-limited scenarios. Due to increased cost, maintenance, and footprint, it is desirable to omit the filtration process in treatment systems utilizing UV for disinfection. However, understanding UV effectiveness for water treatment is primarily based on studies that have assumed pre-filtration and removal of particulates. To identify potential issues with applying UV to unfiltered water sources, this study investigated the effect of the water quality characteristics of unfiltered water samples on UV disinfection efficacy. UV biodosimetry tests were conducted over a year using water samples from two treatment plants that apply UV without filtration. The results showed that instead of typical water quality parameters such as turbidity and UV absorbance, the surface charge of particulate matter is the principal characteristic that describes UV dose-response relationships for unfiltered water sources. In terms of photocatalytic disinfection, this thesis focused on identifying possible interference of background natural organic matter (NOM) on photocatalytic disinfection via a novel metal-free visible-light active material, carbon nitride (CNx). In addition, any potential changes of the photocatalytic process on the character of background NOM was investigated using fluorescence spectroscopy. The results indicated that despite decreased inactivation efficiency of UV-LED disinfection system due to the particulate effect in unfiltered water samples, particles and NOM in real water matrices promoted viral inactivation by CNx photocatalytic disinfection. In addition, the results showed that even with low CNx concentrations (50 mg/L), the viral inactivation rate increased by 43%. Last but not least, the common regulatory drinking water treatment objective of 4-log removal of viruses can be satisfied with a far lower power light source.