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
- 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 Three Valleys Water PLC 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.
Three Valleys Water continues to supply you with drinking water of a high quality. The number of results not meeting the standards fell consistently between 1991 and 1996, and this improvement has been maintained during 1998 when 99.76% of more than 69,250 tests met the standards. This is similar to 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 Three Valleys 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 Three Valleys Water to improve its performance.
2. Bacteria
Whenever bacteria are found in water samples Three Valleys Water investigates immediately.
Low numbers of bacteria were detected in the water leaving 5 water treatment works during 1998. Low numbers of bacteria were also found at 17 service reservoirs. The bacteria found were not harmful to consumers' health. Where necessary the Company has taken remedial action to prevent further failure. The number of bacteriological failures at consumers' taps was not significantly different from previous years. Some failures may have been due to the condition of the tap and not the water itself.
3. Pesticides
Three Valleys Water carried out more than 4,700 tests for individual pesticides during 1998 and all except two met the stringent standard. This reflects the significant investment in recent years to install treatment to remove pesticides from drinking water. There was a significant reduction in 1997 in the number of failures for atrazine and this improvment has been sustained. The Inspectorate considered the two failures in 1998 to be not significant.
4. Lead
Three samples taken by Three Valleys Water failed the standard for lead. The Drinking Water Inspectorate has required the Company to carry out remedial action. The 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 form 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 increased slightly from 1997 and four samples failed the standard in 1998. These were either considered to be not significant or were covered by an undertaking by the Company to carry out work to rectify the problem. No samples failed the standard for manganese. 13 samples failed the standard for PAH during 1998, all of which were considered by the Inspectorate to be not significant. Improvements over recent years reflect the impact of the programme of work being carried out by Three Valleys Water to renovate its distribution system. The programme of work is ongoing, with Three Valleys Water being required to renovate more than 1,026 km of mains by 2008.
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 Three Valleys Water's water treatment works during 1998.
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
In November 1998 advice to boil water was issued to a small number of consumers in the Wembley area following detection of bacteriological contamination of part of the distribution system. This remains under consideration by the Inspectorate.
The Inspectorate completed its assessment of incidents involving an increase in the number of cases of cryptosporidiosis in Welwyn Garden City and Hatfield in March 1997, and in Luton and South Bedfordshire in February and March 1997. It was not possible to determine with certainty the exact cause of the increase in cases and there was no evidence that water was involved. In response to recommendations from the Inspectorate the Company subsequently modified some of its procedures.
The Inspectorate also completed its assessment of the incident involving an outbreak of cryptosporidiosis in West Herts and North London in February and March 1997. Although the Inspectorate considered that there were grounds for concluding that the Company supplied unfit water, after legal advice it decided not to pursue the case through the courts. The Inspectorate made 19 recommendations to the Company which revised some of its procedures or otherwise took appropriate action. Arising from this investigation the Inspectorate also made recommendations to all water Companies.
8. Determinations in 1998
Parameter
Total
Contravening PCV No % Coliforms 6363 23 0.4 Faecal coliforms 6364 3 < 0.1 Colour 422 0 0.0 Turbidity 2915 1 < 0.1 Odour 432 0 0.0 Taste 432 0 0.0 Hydrogen ion 2856 0 0.0 Nitrate 739 0 0.0 Nitrite 912 92 10.1 Aluminium 463 0 0.0 Iron 1752 4 0.2 Manganese 477 0 0.0 Lead 309 3 1.0 PAH 353 13 3.7 Trihalomethanes 196 0 0.0 Total pesticides 782 0 0.0 Atrazine 503 1 0.2 Chlorotoluron 347 0 0.0 2,4-D 197 0 0.0 Diuron 347 0 0.0 Isoproturon 343 0 0.0 Mecoprop 202 0 0.0 Simazine 510 1 0.2 Other pesticides 2252 0 0.0 All others 13156 0 0.0 TOTAL
43642
141
0.3
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Drinking Water Inspectorate,
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Updated 11 July 2001
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