Archive:
(for archive/historical purposes, this document has not been updated)Index of Contents:
- Introduction
- Bacteria
- Lead
- Iron and Manganese
- Cryptosporidium
- Trihalomethanes
- 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 document summarises the results of our checks on Dwr Cymru Welsh Water during 1999 and should be read in conjunction with DWI's "How Good is the Drinking Water?" leaflet which is available here and also from us free of charge from the address at the end of this document.
Dwr Cymru Welsh Water continues to supply you with drinking water of a high quality. In 1999, 99.77% of more than 180,700 tests met the standards. This is below the overall figure for England and Wales of 99.82%.
None of the failures in 1999 were likely to harm consumers' health. We assessed each one and, where necessary, we have required Dwr Cymru Welsh Water to take action to prevent further failures.
Although the 1999 results are good, we know that there are some matters of everyday concern to consumers. These are detailed below including the steps taken by Dwr Cymru Welsh Water to further improve its performance.
2. Bacteria
Whenever bacteria are found in water samples Dwr Cymru Welsh Water investigates immediately.
Occasionally low numbers of bacteria were detected in the water leaving a small number of water treatment works during 1999. The bacteria found were not harmful to health. The Inspectorate was concerned about failures at one works and is requiring the Company to carry out improvements. The Inspectorate is concerned about the failures at two of these service reservoirs and is requiring the Company to carry out improvements. However, there have been significant decreases over the last three years in the number of samples containing bacteria from treatment works, service reservoir and consumers' taps. The number of failures at consumers' taps was 0.4% of the samples taken. Many of these could be due to the condition of the tap and not the water itself.
3. Lead
Samples occasionally fail the standard for lead, even where additional treatment has been installed to reduce the amount of lead picked up by water from pipework. In many cases this is due to the consumer's water pipes being made of lead. In all cases the householder has been informed of things they can do to reduce lead levels at their tap. 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 here and from us free of charge from the address at the end of this document.
4. Iron and Manganese
These two 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 manganese and iron standard has reduced this year compared to the past two years. The overall improvement reflects the impact of the programme of work being carried out by Dwr Cymru Welsh Water to renovate its system. Dwr Cymru Welsh Water has recently completed a programme to renovate 1,900km of water mains between 1995 and 2000. This programme of improvement is ongoing, with Dwr Cymru Welsh Water required to renovate a further 4,786km of mains by 2010.
5. Cryptosporidium
Cryptosporidium is a tiny micro-organism that can sometimes cause a form of diarrhoea called cryptosporidiosis. There are a number of sources of Cryptosporidium other than water but due to new regulations water companies are now required by law to sample continuously and analyse daily for Cryptosporidium in the treated water at those sites which have a potential vulnerability. All water companies had to initially conduct risk assessments at their sites to identify if there was any significant risk of contamination. Dwr Cymru Welsh Water identified that there was significant risk at 40 of its sites and it is now continuously sampling and monitoring the treated water at 27 of these sites, the other 13 are not in use. At all these sites, the Company is required to ensure adequate treatment is in place and it is an offence if the new treatment standard for Cryptosporidium is exceeded. In addition to the regulatory requirement, the Company is able to get early warning of any treatment problems from this monitoring system.
6. Trihalomethanes
The steady downward trend in percentage of zones contravening the standard for trihalomethanes (THM) which has been apparent since 1992 was reversed since 1997, with the past three years showing a significant increase. Enforcement action is being considered for five of the zones. The increase may be due to destabilisation of the peat deposits in the drought of 1995 leading to the delayed increase in leaching of organic material.
7. Drinking Water Quality Incidents
Nine incidents in which drinking water quality deteriorated were reported to the Inspectorate during 1999. Seven of the incidents involved the supply of discoloured water, one involved the detection of taste and odour in supply and one was a disinfection failure. Two of the discolouration incidents remain under consideration by the Inspectorate. Discoloured water was supplied twice to the areas of Milford Haven and St Asaph and once to the areas of Pembroke, Rhyl and Ebbw Vale following mains bursts or work on the distribution system. In June, a precautionary advice to boil water was issued to consumers in four villages in Herefordshire following loss of disinfection at Leintwardine treatment works. However, all samples taken in distribution were found to be satisfactory. In August and September, there was an earthy taste to the water supply from Bryngwyn Water Treatment Works caused by a naturally occurring metabolite from algae. The Company enhanced treatment at the works to improve the taste.
8. Determinations in 1999
Parameter
Total
Contravening PCV No % Coliforms 9432 33 0.4 Faecal coliforms 9433 2 < 0.1 Colour 988 0 0.0 Turbidity 1090 1 0.1 Odour 1387 3 0.2 Taste 1381 1 0.1 Hydrogen ion 1182 5 0.4 Nitrate 910 0 0.0 Nitrite 1954 123 6.3 Aluminium 1154 3 0.3 Iron 2660 62 2.3 Manganese 1515 9 0.6 Lead 516 3 0.6 PAH 1019 67 6.6 Trihalomethanes 779 12 1.5 Total pesticides 1162 2 0.2 Asulam 793 0 0.0 Atrazine 751 2 0.3 2,4-D 628 1 0.2 2,4-DB 627 0 0.0 Carbendazim 559 1 0.2 Linuron 746 1 0.1 MCPA 631 1 0.2 MCPB 621 0 0.0 Mecoprop 623 1 0.2 Mancozeb 568 1 0.2 Trietazine 748 0 0.0 Other pesticides 23766 0 0.0 Antimony 203 0 0.0 Benzo-3-4,pyrene 1019 2 0.2 Oxidisability 192 1 0.5 Temperature 9314 0 0.0 Zinc 213 0 0.0 All others 11949 0 0.0 Total 90513 337 0.4
[ Previous ] [ Contents ] [ Next ]
| A - Z Index | Business and Technical | Consumer Information | Contacting us |
| DWI Home Page | News | Product Approval | Search our site | Wales |
Drinking Water Inspectorate,
Floor 2/A1, Ashdown House, 123 Victoria Street, London, SW1E 6DE
Telephone : 020 7944 5956 - Facsimile : 020 7944 5969
E-mail: dwi_enquiries@detr.gov.uk
Published 12 July 2000 / Updated 11 July 2001
Return to Publications and Reports Index
Return to Drinking Water Inspectorate Home Page
Department for Environment, Food & Rural Affairs (DEFRA)Home Page
The National Assembly for Wales / Cynulliad Cenedlaethol Cymru Home Page
Web site terms
© Crown copyright 2001