Kinetics and Mechanisms of Human Adenovirus 2 Inactivation With UV and Chlorine

Abstract

In the United States, the EPA issues rules for water treatment plants, listing the pathogens that must be inactivated to ensure the safety of the water supply. A wide range of treatment strategies are used by the numerous water utilities because the most efficient methods are not standardized and because the byproducts of free chlorine are under increasing scrutiny. The methodology of water treatment is further complicated by emerging threats to potable water. Of particular interest are adenoviruses, which are on the CCL2 issued by the EPA. Unfortunately, the recently-adopted method of irradiation by ultraviolet (UV) light is largely ineffective against adenoviruses. Research is therefore required to find whether any of the other commonly-used treatments, separately or together, can be effective against this threat. I therefore tested the efficacy of monochloramine for inactivating adenoviruses at numerous variations of pH and temperature. Relatedly, a biological investigation of the mechanisms of virus inactivation (by UV light and monochloramine) was undertaken. Subsequently, a test of sequential treatment of virions, first by UV light and then by monochloramine, was performed to discover a possible synergistic effect. Finally, an alternative sequential treatment, first by decreased free chlorine and then by monochloramine, was also tested for efficacy. Biologically, I found that both monochloramine and UV irradiation inhibit an early phase of virus replication, a step prior to the synthesis of E1A. My extensive characterization of the effects of pH and temperature show that monochloramine accomplishes less inactivation of adenoviruses in conditions of high pH and/or low temperature. My tests also show that sequential treatments of either UV light/monochloramine or reduced dosage of free chlorine/monochloramine show no synergy in inactivating adenoviruses. As a result of this work, it is clear that novel disinfection strategies are required to meet the challenge of adenovirus disinfection.