Date of Award

Spring 1-1-2012

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Karl G. Linden

Second Advisor

James P. Malley

Third Advisor

Kevin M. McCabe

Abstract

Ultraviolet (UV) light is an attractive disinfectant for water due to its lack of byproduct formation and ability to disinfect some organisms that are resistant to chlorine, such as Cryptosporidium parvum. However recent regulations by the USEPA have limited the use of UV disinfection for virus disinfection of groundwater supplies and raised the required dose for inactivation of viruses in surface water supplies. The reasoning behind these restrictions is the well documented resistance of one particular virus to UV disinfection. Adenovirus has changed the regulations regarding UV disinfection because it has been observed to require up to four times the dose of almost all other known pathogens to achieve 4-log (99.99%) inactivation. .

Although its resistance to traditional monochromatic low pressure (LP) UV lamps is well known, adenovirus has been observed to be more susceptible to disinfection by polychromatic medium pressure (MP) lamps. The reason behind this has been investigated and it has been hypothesized that the polychromatic wavelengths emitted by MP lamps have the potential to disrupt the virus particle via different mechanisms than LP UV lamps. This idea was investigated further in this thesis, by the use of a polymerase chain reaction (PCR) assay to quantify damage to DNA and the use of an enzyme linked immunosorbent assay (ELISA) to examine damage to capsid proteins following both types of UV radiation.

In addition to studying the mechanism of action of different types of UV light, there is an interest in developing methods to improve the disinfection potential of adenovirus with the use of UV light. In this thesis the addition of H2O2 to LP UV exposure was shown to increase the inactivation potential over LP UV alone. This combination is an advanced oxidation process (AOP) and produces hydroxyl radicals. These radicals are non-specific oxidants and can be used to degrade chemical contaminants at high UV doses. The doses typically used in UV disinfection are one to two orders of magnitude lower than typical AOP doses. Even with the low dose UV and low levels of H2O2, hydroxyl radicals were sufficiently produced to cause enhanced disinfection. This provides a potential tool for systems with LP UV in place to increase their inactivation credit for adenovirus without changing the type of UV lamp used.

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