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Revised Drinking Water Directive

The existing Drinking Water Directive has been extensively revised and has now been issued as a European Council Directive 98/83/EC. It is an important piece of legislation. This is because it specifies the standards required to ensure water is safe for human consumption. In addition it will drive major change and investment in the UK water industry. The capital cost of implementing the revised directive has been estimated by OFWAT at 2.3 billion.

Timing of the revised drinking water directive

The Directive has been implemented in England by the Water Supply (Water Quality) Regulations 2000. These Regulations contain all the standards required by the Directive and some additional national standards. Nearly all the standards in the 2000 Regulations will come into force on 25 December 2003, including the interim standard for lead of 25 microgrammes/litre. The final standard for lead of 10 microgrammes / litre comes into force on 25 December 2013..

Brief overview of the main changes

The revised directive imposes some new mandatory standards for microbiological and chemical parameters, however others are removed. The eight new parameters are: acrylamide, epichlorohydrin, vinyl chloride, benzene, bromate, 1,2 dichloroethane and two radioactive measures - tritium and total indicative dose. Nine parameters have been tightened: antimony, arsenic (50 microgram down to 10), boron, chloride, copper, lead, nickel, PAH and tri/tetra chloroethenes. Others have been eased or removed. Of particular significance there will no longer be a quantified standard for colour or turbidity. However it is probable that in consultation with the Water Companies the DWI will maintain quantified standards for these two parameters.

Effects on the treatment process

The new lead standard will lead to widespread phosphate dosing, for example, 90% of all Yorkshire water treatment works in the next two years. The new bromate standard will affect OSEC, hypochlorite dosing and ozone use. Extensive use of pH control may become common place. Groundwater sources are likely to need treatment for arsenic. The standards may well lead to the development of purer treatment chemicals for example low bromine hypochlorite, as well as significantly tighter control of the process. THM's will be a particular problem for coloured upland water sources. It is likely that post absorption with GAC will be required followed by re-chlorination.


OFWAT estimates capital expenditure of 2.3 billion (Water Company estimate is 3.1 billion). However the major challenge will be to design new processes that not only minimise capital expenditure but also do not lead to excessive operating cost increases.


The new directive is seen as a major improvement and is based heavily on existing UK good practise. However with the need for positive communication to customers and some standards changing it will be a major PR battle for the Water Companies. It will require them to assure their customers that water quality has not deteriorated.


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