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Analysis and researchers need to do further work to make these technologies more efficient and affordable for commercial use. Alternative Primary Disinfectants DBP formation is primarily influenced by disinfectant type, dose, reaction time, temperature, and pH. Chlorine is the most commonly used oxidizing agent for primary disinfec- tion. But its use has been criticized because it produces high amounts of THMs and HAAs. For this reason, many suppliers want to switch to alternative means, such as ozone and ultraviolet (UV) disinfection, which are superior choices for primary disinfection and produce little to no THMs and HAAs. Although the raw drinking water quality, the nature of organic precursors, and the amount of bac- terial contamination will rule the decision on disinfectant choice, ozone and UV are gaining popularity among water suppliers. Ozone has been a popular choice for bottled water sup- pliers, but most water suppliers hesitate to try this tech- nology for a variety of reasons. The technology is widely accepted in the UK and Netherlands, but the U.S. has some catching up to do. Ozone is a powerful disinfectant and produces very low concentrations of DBPs. However, the issue with ozone is that it does not remove organics from water, which triggers DBP formation after second- ary disinfection. Also, it is not a good disinfectant to treat water with high pesticide and bromate contents because it oxidizes them into more toxic epoxides and bromates. It also produces unknown byproducts that trigger micro- bial growth in GAC. It is recommended to use GAC filters before ozone treatment to minimize byproducts formation and subsequent regrowth of microorganisms in finished water. Consequently, ozone-based disinfection requires periodic replacement of GAC filters, thus raising the over- all cost of water treatment. UV is another attractive alternative for primary disinfec- tion because it produces no byproducts. It is more effec- tive than chlorine in killing cryptosporidium and other pathogens. New York City recently opened the world's largest UV drinking water treatment facility. This $1.5 billion facility serves 9 million residents and provides treatment specifically for cryptosporidium and giardia. UV works best when combined with high-grade GAC filters to minimize DBP formation. Although the high cost of UV-bulbs has been a discouraging factor for several water suppliers, low maintenance and operational expenses can lower the overall treatment cost. The business of UV-based treatment technology has tripled in the U.S. in last six years and is rapidly gaining acceptance in the water industry. Also, several countries in Europe, the Middle East, and Asia are offering subsidies to promote UV technology in the water treatment industry. Paradigm Shift The DBP paradigm is shifting from the nine regulated THMs and HAAs to emerging DBPs such as nitrosamines, halonitriles, haloamides, halonitromethanes, and iodinat- ed aldehydes. With the growing evidence of nitrosamines' toxicity in humans, they are anticipated to be included in the national drinking water regulations as they are at the state level in California and Massachusetts. Recent studies have found that nitrosamines are more genotoxic, cytotoxic, and carcinogenic than the regulated THMs and HAAs (Richardson et al., 2007). The toxicological review of such studies takes years and will not impact water sup- pliers in the near future. However, it is possible that some of the emerging DBPs will eventually end up being on the list of regulated DBPs. The treatment difficulties due to the variability in raw water quality, the complex nature of DBPs, and growing health evidence will continue to pose challenges for water suppliers to comply with the regulations. They need to remain in dynamic mode and continue to upgrade their technology to keep up with ever-changing regulations on DBPs in order to protect community health. References Kristiana, I., Joll, C., Heitz, A. Powdered activated carbon coupled with enhanced coagulation for natural organic matter removal and disinfection byproduct control: application in a Western Australian water treatment plant. Chemosphere 2011, 83 (5), 661-667. Parvez, S., Rivera-Núñez, Z., Meyer, A., Wright, J.M. Temporal variability in Trihalomethane and Haloacetic Acid concentrations in Massachusetts Public Drinking Water Systems. Environmental Research 2011, 111, 499-509, 2011 Richardson, SD, Plewa, MJ, Wagner, ED, Schoeny, R, and DeMarini, DM. Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection byproducts in drinking water: A review and roadmap for research. Mutation Research 2007, 636, 178-242. 30 Shahid Parvez is an assistant professor at the Indiana University Fairbanks School of Public Health. He studies disinfection byproducts for their formation, exposure, toxicity, and health risk. He completed his postdoctoral training at the U.S. Environmental Protection Agency and earned a Ph.D. from the Indian Institute of Technology in Bombay. As the problem of DBPs has risen, so has the popularity of UV. wateronline.com ■ Water Online The Magazine Photo credit: WEDECO – a Xylem brand 2 9 _ V E R T _ 0 5 1 4 C l e a n w a t e r _ I n d i a n a _ D G . i n d d 2 29_VERT_0514 Cleanwater_Indiana_DG.indd 2 4 / 2 1 / 2 0 1 4 3 : 0 9 : 0 8 P M 4/21/2014 3:09:08 PM