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Drinking Water

Volume 165: debated on Friday 19 January 1990

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To ask the Secretary of State for the Environment what is the percentage of drinking water, by volume, in England that is treated by the addition of (a) chlorine and (b) ozone.

[holding answer 15 January 1990]: Precise information is not available. However, I understand that more than 99 per cent. of water supplies in England are treated by the addition of chlorine as a disinfectant. At only six sites, which produce less than 1 per cent. of water supplies, is water treated by the addition of ozone. It is important to note that even when ozone is used in the treatment of drinking water, chlorine is normally added at the final treatment stage to provide for residual disinfection.