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Assessment of a distribution system nitrification critical threshold concept
Results from bench‐scale studies using annular reactors and full‐scale distribution system data were used to evaluate a proposed critical threshold concept (0.05 mg/L nitrite‐nitrogen [NO2–‐N], as proposed by others) for confirming nitrification in chloraminated distribution systems. Bench‐scale data indicated that nitrification occurred at 12 and 22°C, in the presence of either 0.05–0.10 mg/L chlorine (Cl2) or 0.2–0.6 mg/L Cl2 monochloramine. As expected, nitrite‐nitrogen levels exceeded 0.05 mg/L more frequently at higher temperatures and lower disinfectant residuals. At full scale, increases in nitrite‐nitrogen levels were always preceded by a loss of total chlorine residual (usually by two to three months). Even though the critical threshold concept is useful for confirming nitrification, nitrite‐nitrogen levels are often site‐specific, and 0.05 mg/L NO2–‐N is too high to be used as a predictor of nitrification. A decline in total chlorine residual, however, can be a useful predictor of nitrification. Nitrification occurred at water temperatures as low as 6°C at full scale.
Assessment of a distribution system nitrification critical threshold concept
Results from bench‐scale studies using annular reactors and full‐scale distribution system data were used to evaluate a proposed critical threshold concept (0.05 mg/L nitrite‐nitrogen [NO2–‐N], as proposed by others) for confirming nitrification in chloraminated distribution systems. Bench‐scale data indicated that nitrification occurred at 12 and 22°C, in the presence of either 0.05–0.10 mg/L chlorine (Cl2) or 0.2–0.6 mg/L Cl2 monochloramine. As expected, nitrite‐nitrogen levels exceeded 0.05 mg/L more frequently at higher temperatures and lower disinfectant residuals. At full scale, increases in nitrite‐nitrogen levels were always preceded by a loss of total chlorine residual (usually by two to three months). Even though the critical threshold concept is useful for confirming nitrification, nitrite‐nitrogen levels are often site‐specific, and 0.05 mg/L NO2–‐N is too high to be used as a predictor of nitrification. A decline in total chlorine residual, however, can be a useful predictor of nitrification. Nitrification occurred at water temperatures as low as 6°C at full scale.
Assessment of a distribution system nitrification critical threshold concept
Pintar, Katarina D.M. (author) / Anderson, William B. (author) / Slawson, Robin M. (author) / Smith, E. Franklyn (author) / Huck, Peter M. (author)
Journal ‐ American Water Works Association ; 97 ; 116-129
2005-07-01
14 pages
Article (Journal)
Electronic Resource
English
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