Comparison of single and multiple dosing of chlorine for water distribution systems

Single and multiple chlorine dosing in drinking water systems were compared using chlorine decay and THM formation models. Previously published data were re-analysed and it was concluded. after fitting an accurate two-reactant model of bulk-water decay, that multiple dosing of chlorine should provide better quality in a distribution system than does a single dose. This result is consistent with the accepted kinetics of chlorine reacting with organic compounds dissolved in water, but contrasts with the conclusions previously published with the data. This suggests that use of the two reactant model for interpretation of even seemingly straightforward experiments is needed to make sound conclusions. It was also verified that the two-reactant model realistically describes chlorine decay curves for surface water and its blends with desalinated water. This whole modelling approach is also shown to be suitable to simulate chlorine and THM profiles in a distribution system supplied from one water source or blends with desalinated water, under either single or multiple chlorine dosing.