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Water Supply: Purification

Volume 715: debated on Tuesday 1 December 2009


Asked by

To ask Her Majesty's Government what proportion of water supplies is contaminated by pesticides; and what is the annual cost of making it fit to drink. [HL238]

The drinking water inspectorate has advised that regulatory risk assessments by water companies in England and Wales have identified one or more pesticides as a potential hazard in 1,156 out of a total of 2,206 raw water sources. These 1,156 raw water sources serve 693 out of the total of 1,265 water treatment works. Measures to safeguard against the risk of pesticides are therefore currently required for about half of all public water supplies.

The measures used are unique to individual water supplies. Typically they involve one or more of the following activities: catchment management, monitoring-led abstraction management, and treatment informed by monitoring using either powdered or granular activated carbon alone or in combination with ozone. Treatment is not necessarily continuous because the risk of pesticides is seasonal; furthermore in some locations the risk is declining or related to a one-off historic event. Additionally, the unique combination of integrated treatment steps in place at each site is designed to address all potential hazards and produce safe, clean drinking water in the most cost-effective way.

The total annual base industry operating cost for water resource management, abstraction and treatment was £584,000,000 in 2008-09. In the same year, the extra operating expenditure to improve drinking water quality for risks from nitrate, lead, trihalomethanes, turbidity, lead and pesticides was around £7,000,000 and capital expenditure related to pesticide safeguards was about £3,000,000.