Ultraviolet (UV) irradiation is being used with increasing regularity as a secondary disinfectant in swimming pool settings. UV is known to be very effective for inactivation of some microbial pathogens that are resistant to chlorine (e.g., Cryptosporidium parvum and Giardia lamblia); however, anecdotal information suggests that UV can also bring about favorable changes in the chemistry of swimming pool waters. Unfortunately, the basic photochemistry of many chlorinated disinfection by-products (DBPs) that are relevant in swimming pool settings is largely undefined. Therefore, experiments were initiated to explore DBP photochemistry. The results of experiments conducted to date indicate that some chlorinated DBPs will undergo chemical changes as a result of exposure to the doses of UV radiation that are commonly applied in swimming pool settings. Some of these reactions appear to proceed via radical formation, thereby opening up other (nonphotochemical) reaction pathways. As such, we have observed that some nonphotochemically active DBPs can undergo chemical change as a result of interactions with other compounds in solution that are photochemically active. E.R. Blatchley, III received his Ph.D. in Civil (Environmental) Engineering from the University of California, Berkeley in 1988. From there, he became an Assistant Professor in the School of Civil Engineering (Environmental Engineering group) at Purdue University. He later was promoted to Associate, then Full Professor. Professor Blatchley teaches and conducts research in the area of physical/chemical processes of environmental engineering. The focus of his research activities is on disinfection processes involving UV radiation, halogens, and combinations.
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