Abstract
An empirical model for the disappearance of chlorine-induced combined oxidant in estuarine water was developed. The initial concentrations and composition of combined oxidant followed the hump and dip type of break-point curve after 1 h. The disappearance of combined oxidant could be approximated by a first-order reaction. However, the decomposition pathway of combined oxidant below the weight ratio of chlorine dose to ammonia nitrogen required for the maximum amount of combined oxidant in the break-point curve ( r p) was clearly different from that above r p. Below r p the decrease in combined oxidant was mainly due to the reaction of monochloramine with bromide in estuarine water. The observed rate constants increased slightly with increase in the weight ratio of chlorine dose to ammonia nitrogen ( C N/ C 0) and/or the concentrations of bromide. Above r p the decomposition rate of combined oxidant was presumably determined by the composition of combined oxidant after 1 h, i.e. the proportions of monochloramine, bromochloramine and dibromamine. The observed rate constants depended primarily on the value of C N/ C 0, regardless of the bromide concentration. Using our proposed model, the maximum persistence of combined oxidant formed in estuarine water could be estimated.
Published Version
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