Disinfection of particle-associated viruses by ultraviolet

Abstract

Viruses are frequently attached onto a variety of particles in natural waters and wastewaters, however relatively little is known about the impact of this viral particleassociation on water treatment processes. This thesis focuses on the impact of particleassociated viruses on ultraviolet (UV) disinfection. Particles smaller than 2 (µm) in diameter were shown to be large enough to protect bacteriophages MS2 and T4 (model viruses) from UV light. This is smaller than the minimum particle size of 7-10 µm for the shielding of coliform bacteria from the UV disinfection of wastewater. In addition, particulate chemical composition, specifically UV-absorbing content such as organic compounds, was a critical factor in the survival of particle-associated bacteriophages exposed to UV light. Particles such as humic acid floe and activated sludge floe were observed to protect attached phage from UV light. The research findings also re-emphasize that viral disinfection studies should account for particle-associated viruses using techniques such as the physico-chemical blending method that was used in this research, since failure to do so can result in significant underestimation of the true virus concentrations. Further, multiple viral surrogates should be used in experimental studies whenever possible, since viruses vary significantly in their sizes, shapes, and surface charges, all of which can influence the adsorption of viruses to particles.