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Rate of chloramine decay at pipe surfaces
Author(s) -
Westbrook Andrew,
Digiano Francis A.
Publication year - 2009
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.1551-8833.2009.tb09924.x
Subject(s) - chloramine , materials science , reaction rate , hydraulics , reaction rate constant , chemistry , mechanics , metallurgy , thermodynamics , chlorine , physics , kinetics , biochemistry , quantum mechanics , catalysis
Characterizing the rate of chloramine loss at pipe surfaces is crucial for predicting the rate of decay within the distribution system (DS). Chloramines in finished water are relatively stable, yet they do autodecompose. However, significant loss of stability can occur in the DS where interaction with pipe surfaces is a major source of chloramine loss. Myriad factors complicate in situ measurement of the surface reaction rate including spatially varying pipe material, age, and condition, as well as temporally varying hydraulics. In this study, a bench‐scale, pipe section reactor was used to determine chloramine surface reaction rate constants for cementlined ductile‐iron pipe and tuberculated, unlined cast‐iron pipe. Chloramine decay was found to be first order for both of these pipe materials. Surface reaction rates were calculated by accounting for the influence of water velocity on mass transfer of chloramine to the pipe surface, and therefore the overall chloramine decay rate. Temperature and pH were varied to determine the effect on surface reaction rates for a range of conditions common to the DS.