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Assessment of a distribution system nitrification critical threshold concept
Author(s) -
Pintar Katarina D.M.,
Anderson William B.,
Slawson Robin M.,
Smith E. Franklyn,
Huck Peter M.
Publication year - 2005
Publication title -
journal ‐ american water works association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.466
H-Index - 74
eISSN - 1551-8833
pISSN - 0003-150X
DOI - 10.1002/j.1551-8833.2005.tb10937.x
Subject(s) - nitrification , nitrite , chloramine , chemistry , nitrogen , environmental chemistry , disinfectant , chlorine , environmental engineering , environmental science , nitrate , organic chemistry
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 [NO 2 – ‐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 (Cl 2 ) or 0.2–0.6 mg/L Cl 2 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 NO 2 – ‐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.