AWWA WQTC62434

AWWA WQTC62434 Assessing UV Cleaning and Fouling Requirements of Lime Softened Water
Conference Proceeding by American Water Works Association, 11/01/2005

Neemann, Jeff; Burns, Nick; Edwards-Brandt, Jessica; Mackey, Heather; Schrempp, Tom; Weber, Chuck

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The use of ultraviolet light (UV) for disinfection of drinking water is arapidly growing market because utilities are using UV to provide anadditional disinfection barrier to pathogens such as Cryptosporidium andGiardia. Many lime-softening plants in the Midwestern United States areinterested in UV technology; however, there still remains some questionabout the stability of lime-softened water and the impact it could have onthe fouling potential of the quartz sleeves of the UV reactor. Some studieshave been conducted to evaluate the impact of hardness on fouling of thesleeves, but not many studies have looked at the long-term foulingpotential of lime softened water. The draft US Environmental Protection Agency (USEPA) UV DisinfectionGuidance Manual (UVDGM) recommends that systems that treat waterwith high hardness and high iron concentrations evaluate the potential forfouling by pilot or demonstration-scale testing. Water District No. 1 ofJohnson County, Kansas (WaterOne), is a large utility that supplies waterto approximately 340,000 people in the Kansas City metropolitan area. Toprovide water of the highest quality to its customers, WaterOne isconsidering the use of UV disinfection at the new facility, and retrofittingits existing facilities with UV disinfection. Therefore, WaterOneconducted a 6 month pilot study to evaluate the potential effects of lime-softenedwater on the UV equipment. The pilot testing consisted of a side-by-side comparison of low pressure high-output (LPHO) and mediumpressure (MP) UV lamps. Both systems were tested using pilot reactorsequipped with on-line UV intensity sensors and a sleeve wiping system.The pilot testing protocol included long-term operation of the UV reactorswhile wiper frequency was varied and the lamp outputs were beingmonitored. In addition, periodically the quartz sleeves were removed andthe transmittance of the sleeves measured. Includes 3 references, tables, figures.