Archive:
(for archive/historical purposes, these documents have not been updated)Index of Contents:
- Introduction
- Bacteria
- Pesticides
- Lead
- Iron and Manganese
- Cryptosporidium
- Trihalomethanes
- Drinking Water Quality Incidents
- Determinations in 1999
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 Yorkshire Water Services Limited 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.
Yorkshire Water continues to supply you with drinking water of a high quality. In 1999, 99.88% of more than 266,700 tests met the standards. This is above 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 Yorkshire 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 Yorkshire Water to further improve its performance.
2. Bacteria
Whenever bacteria are found in water samples Yorkshire Water investigates immediately.
Occasionally low numbers of bacteria were detected in the water leaving water treatment works and service reservoirs during 1999. The number of works involved was lowest since 1996 and the bacteria found were not harmful to consumers' health. There was a significant reduction in 1999 in the number of service reservoirs, and samples from service reservoirs, in which bacteria was detected. In all cases the Company has taken remedial action. The number of bacteriological failures at consumers' taps remains similar at around 0.5% of the samples taken. Many of these failures could be due to the condition of the tap, rather than the water itself, but the Inspectorate is requiring the Company to take further action in one water supply zone.
3. Pesticides
Yorkshire Water carried out more than 80,000 tests for individual pesticides during 1999 and, for the first time since 1990, all met the stringent standard. This reflects the significant investment in recent years to install treatment to remove pesticides from drinking water.
4. 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. Only five out of 1,287 samples failed to meet the standard during 1999, reflecting the benefits of the additional treatment. In all cases 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 here and from us free of charge from the address at the end of this document.
5. Iron and Manganese
These parameters provide a good indication of the overall condition of the mains used to distribute drinking water through the region.
The number of zones failing the standard for iron has fallen significantly since 1998. This improvement reflects the impact of the programme of work being carried out by Yorkshire Water to renovate its distribution system. This programme of work is ongoing, with the Company being required to renovate more than 5,385 km of mains by the end of 2010.
6. Cryptosporidium
Cryptosporidium is a tiny micro-organism that can sometimes cause a form of diarrhoea called cryptosporidiosis. Low numbers of Cryptosporidium oocysts were detected in the treated water leaving the old Tophill Low water treatment works in January 1999 and Loftsome Bridge water treatment works in April 1999.
Due to new regulations water companies are required by law to sample continuously and analyse daily for Cryptosporidium in the treated water at their most vulnerable sites. It is an offence if they fail to meet the new treatment standard.
All water companies had to initially conduct risk assessments at their sites to identify if there was any significant risk of contamination. Yorkshire Water found that there was significant risk at 33 of its sites, a number of which are to be abandoned or have additional treatment installed. The Company is installing additional treatment at five sites to ensure that any Cryptosporidium oocysts, which may from time to time be present in the source water, are removed. The Company is also continuously sampling and monitoring the treated water at seven sites. In addition to the regulatory requirement, the company is able to get early warning of problems from this monitoring system.
7. Trihalomethanes (THMs)
Trihalomethanes are a group of compounds which can be formed during the disinfection process. The standard is very stringent and it is not unusual to have intermittent failures. The increased failure rate noted in 1997 and 1998 has not been repeated during 1999 and the number of water supply zones failing the standard has fallen to three.
8. Drinking Water Quality Incidents
Yorkshire Water notified the Inspectorate of 26 incidents in which drinking water quality deteriorated, during 1999.
Thirteen incidents have been assessed. Eight of these involved the supply of discoloured water at various locations in Yorkshire, including discolouration of supplies following sudden and unexpected deterioration in the raw water quality at Osmotherley water treatment works in June 1999 and at Thornton Steward water treatment works in July 1999; one involved localised bacteriological contamination of the water supplied to the village of Blades in May 1999; two involved loss of disinfection at water treatment works; and two involved the detection of low numbers of Cryptosporidium oocysts in the treated water leaving water treatment works.
Also during 1999, assessments were completed of three incidents involving the supply of discoloured water to parts of Harrogate in May 1998, parts of Harrogate and Knaresborough in September 1998 and parts of Boroughbridge in December 1998.
The Inspectorate made several recommendations to the Company following these assessments, to which the Company has responded positively.
Of the 13 incidents occurring in 1999 still under consideration, 11 relate to the supply of discoloured water following the disturbance of mains sediments, one relates to taste, odour and discolouration problems following the commissioning of the new Tophill Low water treatment works in June 1999; and one relates to the ongoing media interest and concerns of consumers in Gillamoor and Farndale over proposed changes to the source of their drinking water.
The Company has elected trial at Crown Court for allegedly supplying water unfit for human consumption during seven further incidents involving the supply of discoloured water. These affected parts of West Leeds in May 1997; parts of Sheffield in December 1997; the Sheepscar area of Leeds in May 1998; parts of Drighlington in June 1998; parts of the Idle Hill area of Leeds in July 1998; Addingham in August 1998; and parts of Boroughbridge and the villages supplied by Marton water treatment works in November 1998.
9. Determinations in 1999
Parameter
Total
Contravening PCV No % Coliforms 12187 59 0.5 Faecal coliforms 12187 12 0.1 Colour 12178 1 < 0.1 Turbidity 12179 20 0.2 Odour 1615 0 0.0 Taste 1612 0 0.0 Hydrogen ion 12181 11 0.1 Nitrate 1726 3 0.2 Nitrite 1783 5 0.3 Aluminium 6354 17 0.3 Iron 6354 82 1.3 Manganese 6354 39 0.6 Lead 1287 5 0.4 PAH 1163 10 0.9 Trihalomethanes 1168 9 0.8 Total pesticides 1048 0 0.0 2,4-D 982 0 0.0 Dichlorprop 982 0 0.0 Diuron 974 0 0.0 Imazypyr 982 0 0.0 Isoproturon 974 0 0.0 MCPA 982 0 0.0 Mecoprop 982 0 0.0 Other pesticides 73640 0 0.0 Benzo 3,4 pyrene 1163 1 0.1 Oxidisability 212 1 0.5 Tetrachloroethene 1144 1 0.1 All others 23818 0 0.0 Total 198211 276 0.1
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Drinking Water Inspectorate,
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Telephone : 020 7944 5956 - Facsimile : 020 7944 5969
E-mail: dwi_enquiries@detr.gov.uk
Published 12 July 2000 / Updated 11 July 2001
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