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The proposed Arsenic Rule currently under review by the Environmental Protection Agency has the potential to present significant challenges to a large number of drinking water purveyors in complying with a lower arsenic standard. SierraPacific Power Company (Sierra) in Reno, Nevada is one of the purveyors that will be affected by the new rule. Sierra's water production occurs from 2 surface water treatment plants and 29 wells. A significant fraction of these production wells have arsenic and Sierra (and its customers) will be affected, though the extent depends upon the standard set in the final rule. For example, if the standard is set at 5 ppb, then 23 of Sierra's 29 wells would violate the maximum contaminant level (MCL). An economical option, in Sierra's estimation, is to utilize the existing conventional treatment plant facilities for the removal ofarsenic from groundwater exceeding the MCL. This paper details the findings from research that was conducted to determine the effectiveness of coagulation for the removal of arsenic from various blends of ground and surface water. Full scaletesting was conducted to determine the arsenic removal effectiveness of the existing treatment process (conventional treatment with alum) at the Glendale Water Treatment Plant. Additional bench-scale evaluation (jar testing) was conducted to determine the influence on arsenic removal of process variables such as pH, coagulant (alum and ferric chloride) and coagulant dose. Optimal arsenic removal via conventional treatment (with alum) occurred in the pH range 5-7.5. Raw water (blended) arsenic concentrations in the range of 25-60 ppb were successfully treated to a final (post-filtration) arsenic concentration lessthan 10 ppb in this pH range (alum dose approximately 20 mg/L). Ferric chloride was also shown to be effective in the same pH range (in bench-scale tests) for blends of well/surface water ranging from 25% to 100% well water. Includes table, figures.

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Edition: Vol. - No. Published: 06/01/2001 Number of Pages: 10File Size: 1 file , 400 KB