ABSTRACT
ABSTRACT: The study and modelling of chlorine decay in distribution systems has been the subject of intense research in the last decade. This paper reports on a series of experiments carried out on a lifescale test rig in order to quantify any possible effect of hydraulic transients on residual chlorine concentrations in drinking water, comparatively to the decay in steady-state flow conditions. The results relate to two types of tests: steady-state tests were run in order to investigate the decay of residual chlorine during steady-state flow, for varying values of the Reynolds number; transient tests comprised an initial steady-state period, followed by successive transient events and a new steady-state period. The transient events were induced by rapid valve closing manoeuvres. The series of results obtained provide evidence towards the existence of a slowing down effect of hydraulic transients on chlorine decay rates, for the conditions represented by the experiment.
