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BIOLOGICAL FILTRATION FOR THE NITRIFICATION OF EXCESSIVE LEVELS OF FREE AMMONIA
Citation:
MOOR, J. AND D. A. LYTLE. BIOLOGICAL FILTRATION FOR THE NITRIFICATION OF EXCESSIVE LEVELS OF FREE AMMONIA. Presented at US EPA WORKSHOP ON INORGANIC CONTAMINANT ISSUES, CINCINNATI, OH, August 21 - 23, 2007.
Description:
Ammonia in source waters can cause water treatment and distribution system problems. Research on the presence of ammonia in drinking water distribution systems for example has suggested some correlation between excess ammonia and increased biological activity (Servais, 1995; Wilczak, 1996), corrosion (Murphy, 1997), formation of nitrite and nitrates (Odell, 1996; Wilczak, 1996) and adverse effects on water’s taste and odor (Bouwer and Crowe, 1988, Rittmann and Huck, 1989). Therefore, in some cases, the removal (or oxidation) of ammonia from water is desirable before distribution (as long as nitrite and nitrate standards are not exceeded). Biological oxidation of ammonia to nitrite and nitrate (nitrification) is well understood and common in wastewater processes. The biological filtration to convert ammonia to nitrate in drinking water applications in full-scale systems is limited in the United States. Biological conversion of ammonia (NH3) to nitrate (NO3-) involves a two-step sequence of reactions mediated by two different genera of bacteria, Nitrosomonas and Nitrobacter. The process is aerobic and the oxygen demand of nitrification is also significant. For complete nitrification, 4.57 mg O2 is required per mg NH4+- N oxidized (U.S. EPA, 1975). In some natural waters in the United States however, ammonia levels well exceed maximum stoichiometric amount of oxygen that can possibly be added to water based on it’s saturation limit. Therefore an innovative approach must be taken that continuously introduce oxygen to the bacteria in an attached setting. The objective of this study was to develop and demonstrate a filtration system that is capable of biological oxidizing excessive levels of ammonia (> 5 mg/L NH3-N).