Distributing drinking water with a low or zero disinfectant residual

Preventing deterioration of the microbiological quality of drinking water during distribution is a
major concern for the water industry. In the United Kingdom, drinking water is distributed with
a disinfectant residual, but in the Netherlands most supplies are distributed without a
disinfectant residual. Drinking water quality standards in both countries are based on the
European Comrnunity Drinking Water Directive. This report describes a study aimed at
evaluating the operational aspects of distributing drinking water with or without a disinfectant
residual. The undesirable effect of a chlorine residual on the taste of drinking water was an
important motive for this study, because customer satisfaction has become increasingly
important for the water industry. The study was conducted as a collaborative project in the
United Kingdom Water Industry Research (UKWIR) programme and in the Joint Research
Prograrnme of the Netherlands Water Supply Companies. The study included (i) a limited
review of the literature conceming the use of a disinfectant during distribution, (ii) a survey of
water quality and operational practices in a number of representative water supplies in the
Netherlands and in the UK, (iii) a comparison between the two countries and (iv) a workshop to
exchange information between water supply companies in both countries.