European regulations on residual disinfection

This article describes the relevant requirements of the European Community Drinking Water Directive and outlines how the European Union's 15 member states and Switzerland have implemented them. European countries vary considerably in their national requirements or guidance on disinfection and the use of disinfectant residuals within the distribution system. Although a few European countries require all water supplies to be disinfected and a disinfectant residual to be maintained, some countries do not require disinfection or the use of a disinfectant residual. Some countries adopt intermediate positions, and many countries have exceeded the directive's requiremnts. A number of factors influence countries' practices, including the nature and quality of their water sources, meteorolgical con,ditions, the degree of treatment provided to remove impurities, concern about disinfection by-products, and the operation and condition of the distribution system. A recently agreed on new Drinking Water Directive is also described.