The effect of nitrification on sampling sites

Formation of nitrite by nitrifying bacteria in distribution systems could affect water parameters associated with disinfection procedures, including chloramine, ammonia, nitrite, nitrate, pH and heterotrophic bacteria. Where pipework was used to convey a sampling feed of plant water to the laborator...

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Bibliographic Details
Published in:Water engineering & management 1997-11, Vol.144 (11), p.22-27
Main Authors: Tokuno, Shin-Ichi, Baker, Floyd
Format: Article
Language:English
Subjects:
Ammonia
Bacteria
Basins
Biofilms
Chemical reactions
Chlorination
Chlorine
Disinfection
Disinfection & disinfectants
Effluents
Laboratories
Measurement
Pathogens
Sampling
Studies
Surface water
Surface waters
Water distribution systems
Water quality
Water treatment
Water treatment plants
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Summary:Formation of nitrite by nitrifying bacteria in distribution systems could affect water parameters associated with disinfection procedures, including chloramine, ammonia, nitrite, nitrate, pH and heterotrophic bacteria. Where pipework was used to convey a sampling feed of plant water to the laboratory, filming by nitrifying bacteria could affect the analytical results. This was demonstrated at the O.N. Stevens plant in Corpus Christi where plant disinfection used chloramine to a concentration of 3.5-4.5 mg per litre in the finished water. Samples obtained from the primary and secondary basins by dipper showed significant differences from samples taken from the basin by the laboratory taps, particularly from the primary basin samples. The chloramine concentrations were significantly reduced in samples from the laboratory taps compared with dipper samples. Washing the pipework with high test hypochlorite solution restored the equivalence of dipper and tap tests and equivalence was also restored when the basin sampling pipework was not in use during a 14 d basin cleaning period, presumably because of the die-back of nitrifying bacteria. Additional plant and laboratory studies were carried out on the effects of nitrite, temperature and sampling vessel on the stability of chloramine. The information collection rule would require more sampling sites and precautionary measures were required to avoid the effects of nitrification on the accurate measurement of chloramine residual.
ISSN:0273-2238