Archive:
(for archive/historical purposes, this document has not been updated)Index of Contents:
- Introduction
- Bacteria
- Pesticides
- Lead
- Iron and Manganese
- Cryptosporidium
- Drinking Water Quality Incidents
- Prosecutions
- Determinations in 1998
1. Introduction
The Drinking Water Inspectorate (DWI) checks that water companies supply water that is safe to drink when it reaches your home. This leaflet summarises the results of our checks on North West Water Limited during 1998 and should be read in conjunction with DWI's "How Good is the Drinking Water ?" leaflet which is available from us free of charge.
North West Water continues to supply you with drinking water of a high quality. In 1998, 99.57% of more than 336,100 tests met the standards. This is below the overall figure for England and Wales of 99.78%.
None of the failures in 1998 were likely to harm consumers' health. We assessed each one and, where necessary, we have required North West Water to take action to prevent further failures.
Although the 1998 results are good, we know that there are some matters of everyday concern to consumers. These are detailed below including the steps taken by North West Water to improve its performance.
2. Bacteria
Whenever bacteria are found in water samples North West Water investigates immediately.
Low numbers of bacteria were detected in the water leaving fifty water treatment works during 1998. The bacteria found were not harmful to consumers' health. The Inspectorate was concerned about the failures at nine works and is requiring the Company to carry out improvements. One service reservoir failed to meet the required standard for total coliforms and the Company has taken remedial action to prevent recurrences of the failures. There have also been occasional bacteriological failures in the water at consumers' taps and the Inspectorate has required the Company to take action in one zone. Many of these failures may be due to the condition of the tap and not the water itself.
3. Pesticides
North West Water carried out more than 30,700 tests for individual pesticides during 1998 and all except five met the stringent standard. This reflects the significant investment in recent years to install treatment to remove pesticides from drinking water. The Inspectorate considered the five failures in 1998 to not be significant.
4. Lead
North West Water continues to have samples occasionally failing the standard for lead, even where additional treatment has been installed to reduce the amount of lead picked up by water from pipework. The Inspectorate has required the Company to take action to reduce the risk of failing the standard in a further 16 zones. In all cases of a failure of the standard, the householder has been informed of the problem. The Drinking Water Inspectorate advises consumers living in properties with lead pipes to seek advice from their water company. A DWI leaflet about lead in drinking water is also available from us free of charge.
5. Iron and Manganese and polycyclic aromatic hydrocarbons (PAH)
These three parameters provide a good indication of the overall condition of the mains used to distribute drinking water through the region.
The number of samples failing the standard for iron and manganese has remained fairly constant since 1992. During 1998, many of the failures for iron, manganese and PAH occurred in areas where the Inspectorate has previously required the Company to start remedial work. The Inspectorate is now requiring the Company to carry out work in a further 18 zones, and the ongoing programme of improvement is requiring North West Water to renovate more than 7,687 km of mains by 2005.
6. Cryptosporidium
Cryptosporidium is a tiny micro-organism which can sometimes cause a form of diarrhoea called cryptosporidiosis. No instances were reported to the Inspectorate of the detection of Cryptosporidium in water leaving North West Water's water treatment works during 1998 although some instances of an increase in the number of cases of cryptosporidiosis have been reported in the Company's area.
Water companies will shortly be required to sample continuously and analyse daily for Cryptosporidium in the treated water at their most vulnerable sites. It will be an offence if they fail to meet a new treatment standard.
7. Drinking Water Quality Incidents
Thirty three incidents were reported to the Inspectorate during 1998. Eighteen of these involved the supply of discoloured water to consumers in Barrow, Blackburn, Darwen (twice), Eccles, Great Sankey, Ormskirk, Rainhill (twice), Rochdale, St Helens, Sudden, Thornton Cleveley, Wallasey, Walney Island, Warrington (twice), and Widnes and were associated with burst mains and their repair or other work on the distribution system. Seven other incidents were associated with partial treatment failures at Franklaw (twice) and Wybersley Water Treatment Works; with operational problems at Hodder Water Treatment Works; when a service reservoir supplying parts of Macclesfield emptied; when a pressure reducing valve in Chorley and Didsbury failed; and following a period of heavy rain in the vicinity of Crummock Water when consumers were supplied with discoloured water from Cornhow Water Treatment Works.
Three incidents involved the issue of precautionary advice to boil water following airlocking of dosing pumps at Borwick Water Treatment Works in January, at Troutbeck Water Treatment Works in February and at Burton Water Treatment Works in August.
Incidents involving the supply of water with taste and odour occurred in Whitworth and Cheadle; the supply of water with a high pH from Whitebull Water Treatment Works; backsiphonage in Widnes; and the issue of precautionary advice to boil water in Bollington, Macclesfield.
8. Prosecutions
During 1998 the Inspectorate completed its assessments of 6 incidents reported in 1997 and 1 which occurred in 1996. One of the 1997 incidents, which involved the supply of discoloured water to parts of Liverpool following a burst 44 inch diameter main, resulted in the Inspectorate initiating legal action. The Company pleaded guilty to supplying water unfit for human consumption at Liverpool Magistrates' court on 5 November 1998 and was fined a total of £3,000, with £2,842 costs.
9. Determinations in 1998
Parameter
Total
Contravening PCV No % Coliforms 21779 134 0.6 Faecal coliforms 21779 7 < 0.1 Colour 12174 6 < 0.1 Turbidity 12172 25 0.2 Odour 2748 3 0.1 Taste 2685 1 < 0.1 Hydrogen ion 8082 30 0.4 Nitrate 2963 0 0.0 Nitrite 3642 1 < 0.1 Aluminium 14642 17 0.1 Iron 14655 333 2.3 Manganese 14642 62 0.4 Lead 14521 333 2.3 PAH 1937 26 1.3 Trihalomethanes 3061 274 9.0 Total pesticides 2467 0 0.0 2,4 D 1691 0 0.0 Atrazine 1688 0 0.0 Diuron 1491 0 0.0 Liuron 1492 0 0.0 MCPA 1691 2 0.1 Mecoprop 1691 3 0.2 Other pesticides 21005 0 0.0 Ammonium 3328 2 0.1 Arsenic 321 0 0.0 Cadmium 315 1 0.3 Copper 1376 1 0.1 Oxidisability 433 2 0.5 Phosphorus 10680 7 0.1 Potassium 377 1 0.3 Surfactants 321 1 0.3 Temperature 3956 2 0.1 All others 37389 0 0.0 Total
243194 1274 0.5
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Updated 11 July 2001
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