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Engineering Design and Operation Report: Biological Treatment Process for the Removal of Ammonia from a Small Drinking Water System in Iowa: Pilot to Full-Scale
Lytle, D., D. Williams, C. Muhlen, M. Pham, K. Kelty, M. Wildman, G. Lang, M. Wilcox, AND M. Kohne. Engineering Design and Operation Report: Biological Treatment Process for the Removal of Ammonia from a Small Drinking Water System in Iowa: Pilot to Full-Scale. US EPA Office of Research and Development, Washington, DC, EPA/600/R-14/336, 2014.
To inform the public
Many regions in the United States have excessive levels of ammonia in their drinking water sources (e.g., ground and surface waters) as a result of naturally occurring processes, agricultural and urban runoff, concentrated animal feeding operations, municipal wastewater treatment plants, and other sources. Ammonia is not regulated by the U.S. Environmental Protection Agency (EPA) as a contaminant. Based on a 2003 World Health Organization (WHO) assessment, ammonia levels in groundwater are typically below 0.2 milligrams per liter (mg/L), and do not pose a direct health concern at levels expected in drinking water (WHO 2003); however, they may pose a concern when nitrification of significant levels of ammonia from the source water occurs in the drinking water distribution system. Specifically, this nitrification, which is the conversion of the ammonia to nitrite and nitrate by bacteria, leads to water quality issues, such as potential corrosion problems, oxidant demand, taste and odor complaints, and elevated nitrite levels (Bremer et al.,2001; Fleming et al., 2005; Lee et al., 1980; Odell et al., 1996; Rittman & Snoeyink, 1984; Suffet et al., 1996). The EPA’s regulatory limits for nitrite and nitrate (at the entry point to the distribution system) are 0.1 and 10 mg N/L, respectively. Ammonia in water may also pose problems with water treatment effectiveness. For example, in source waters containing both ammonia and arsenic, the ammonia may negatively impact the removal of arsenic by creating a chlorine demand, therefore reducing the availability of chlorine needed to oxidize the arsenic (Lytle et al., 2007). Lastly, water systems that have ammonia in their source water and desire to maintain a free chlorine residual will need to add additional chlorine to overcome the demand of ammonia, or have potential difficulty in meeting contact times needed to achieve disinfection goals. Clearly, the complete oxidation of source water ammonia prior to or as part of the water treatment process would eliminate the potential negative impacts of nitrification on distribution system water quality.