Advances in Water Treatment and Enviromental Management

Chapter 13OPTIMISATION OF SECONDARYCHLORINATION PRACTICE IN THEUKC R Hayes (Water Quality Management, UK), A Elphick(Consultant, UK)SUMMARYThe need for boosting chlorine concentrations within water supply distributionnetworks is reviewed in relation to UK practice and recent changes in the UK’swater legislation. Comparisons are made between UK practices and those of otherEuropean States.There is a need to clarify better several microbiological quality issues, in order to beable to define more objective approaches to the management of chlorination.Irrespective of these current uncertainties, it is concluded that secondary chlorinationwill be increasingly necessary in the UK, at least in the short to medium term. Thisview relates to the technical challenge of achieving microbiological, aesthetic (eg.taste) and chemical (eg. trihalomethanes and nitrite) standards within the next fewyears to satisfy legislative demands.An objective approach is proposed for managing chlorine residuals within distributionnetworks, based on the specification of target minimum concentrations. Itsimplementation in any network will require preliminary investigations to determinethe need for secondary dosing; if such dosing is required, it will then be necessaryto select appropriate doses and dosing points. Such investigations might besupported by a secondary chlorination model.The design and use of chlorination plant, in respect of secondary dosing applicationsand for optimisation studies, are reviewed.INTRODUCTIONThe benefits of maintaining chlorine residuals throughout a water supply distributionnetwork have often been perceived to be:(i)(ii)the suppression of bacterial regrowth and the preservation of generalsanitary conditionthe provision of a buffer against low level contamination(iii) the presence of a chemical indicator to detect gross contamination© 1991 Elsevier Science Publishers Ltd, EnglandWater Treatment—Proceedings of the 1 st International Conference, pp. 131–140131