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Potable water treatment
Potable water treatment

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4.11 Plumbo-solvency

Many water supplies in the UK are naturally acidic, and when this type of water is supplied through lead pipes the lead dissolves into the water. Lead pipes are dominant in many older established areas. The Drinking Water Directive has set a maximum admissible concentration of 10 μg 1−1 lead in water, to be achieved by the year 2013. The obvious solution to this problem is to remove all lead piping but this is a costly exercise. As an interim measure, the water leaving the treatment works can be dosed with lime or phosphate to increase the pH to 8.0–8.5 (making the water less acidic), thus reducing the extent to which the lead dissolves in the water. The solubility of lead is much reduced in hard water where the lead is precipitated as insoluble lead carbonate. Another practical measure (in the home) is to let the water run for a minute or two before using it. This is especially advisable in the morning when the lead concentration in the water may be high because the water has stood in the pipes overnight.