Archive:
(for archive/historical purposes, this document has not been updated)Index of Contents:
- Introduction
- Bacteria
- Pesticides
- Lead
- Iron and Manganese
- Trihalomethanes
- 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 Yorkshire Water Services 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.
Yorkshire Water continues to supply you with drinking water of a high quality. Although overall compliance with the standards has remained fairly steady at around 99.75% since 1994, during 1998 there has were fewer results failing to meet the standard. For 1998, 99.81% of more than 268,100 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 Yorkshire 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 Yorkshire Water to 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 a small number of water treatment works during 1998. The number of works involved was very similar to 1997 and the bacteria found were not harmful to consumers' health. The Inspectorate was concerned about the failures at one works but this is no longer in supply. The number of service reservoirs failing the required standards during 1998 was also similar to that for previous years. In some cases the Company has already taken remedial action, but in five cases the Inspectorate is requiring it to take action. The number of bacteriological failures at consumers' taps remains at around 0.7% of the samples taken. Many of these failures maybe due to the condition of the tap and not the water itself.
3. Pesticides
Yorkshire Water carried out more than 81,000 tests for individual pesticides during 1998 and only 4 results failed to meet the stringent standard. This reflects the significant investment in recent years to install treatment to remove pesticides from drinking water.
4. Lead
Yorkshire 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. 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 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.
There has been a decrease in the number of samples failing the standards for iron and PAH has decreased when compared to earlier years. The biggest change for 1998 has been in the significant reduction in the number of samples failing the standard for manganese. This improvement reflects the impact of the programme of work being carried out by Yorkshire Water to renovate its distribution system. The programme of improvement is ongoing, with Yorkshire Water being required to renovate more than 5,385 km of mains by 2010. However the Inspectorate remains very concerned at the number of incidents in the Yorkshire area where discoloured water is supplied because mains sediments have been disturbed.
6. 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. There was an increase in the number of water supply zones failing the standard in 1997 and a similar number have failed in 1998. Yorkshire Water is being required to take action at Albert water treatment works which supplies some of these zones.
7. Cryptosporidium
Cryptosporidium is a tiny micro-organism which can sometimes cause a form of diarrhoea called cryptosporidiosis. Although cryptosporidium oocysts were detected on a number of occasions in some of the raw waters, no instances were reported to the Inspectorate of the detection of oocysts in the water leaving Yorkshire 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.
8. Drinking Water Quality Incidents
Yorkshire Water notified the Inspectorate of 15 incidents during 1998.
Seven incidents have been assessed. One involved the supply of discoloured water to parts of Mirfield in January 1998, the cause of which was never found; a disinfection failure at Rudland Slack water treatment works in June 1998; low level bacteriological contamination of a service reservoir and the associated distribution system at Baildon in June 1998; bacteriological contamination of the distribution system supplied from Grenoside service reservoir which resulted in advice to boil water being issued to 2,300 properties in the Chapeltown and Oughtibridge area of Sheffield in August 1998; the supply of discoloured water to the Chapeltown and Oughtibridge areas of Sheffield in September 1998 following vandalism at a service reservoir; bacteriological contamination of a small part of the Barnsley distribution system following mains refurbishment in September 1998; and the supply of discoloured water to parts of Bradford following a repair to a burst main in December 1998.
Also during 1998, the Inspectorate completed assessments of three incidents involving the supply of discoloured water to parts of Bradford in December 1996, May 1997 and August 1997, all of which were associated with work on the distribution system; an incident involving the supply of discoloured water to parts of north Sheffield in December 1996, following planned work on the distribution system; and a further incident involving the supply of discoloured water to the Haxey area in June 1997 following a burst main.
The Inspectorate made several recommendations to the Company following these assessments and the Company has responded by reviewing a number of its procedures.
Of the eight 1998 incidents still under consideration, seven relate to the supply of discoloured water associated with planned work on the distribution system in Leeds, Bradford, Harrogate and the Boroughbridge area and one relates to the supply of discoloured water following a partial treatment failure at Addingham water treatment works. Two further incidents from 1997, both involving the supply of discoloured water, also remain under consideration.
9. Determinations in 1998
Parameter
Total
Contravening PCV No % Coliforms 12018 79 0.7 Faecal coliforms 12018 4 < 0.1 Colour 12015 2 < 0.1 Turbidity 12012 34 0.3 Odour 1577 0 0.0 Taste 1576 0 0.0 Hydrogen ion 12016 18 0.1 Nitrate 1717 4 0.2 Nitrite 1811 2 0.1 Aluminium 6239 16 0.3 Iron 6241 120 1.9 Manganese 6239 32 0.5 Lead 1505 18 1.2 PAH 1215 19 1.6 Trihalomethanes 1088 30 2.8 Total pesticides 1198 0 0.0 2,4-D 1069 0 0.0 Dichlorprop 1061 0 0.0 Diuron 1109 1 0.1 Heptachlor 941 0 0.0 Imazapyr 1041 1 0.1 Isoproturon 1109 0 0.0 Linuron 1109 0 0.0 MCPA 1070 1 0.1 Mecoprop 1070 1 0.1 Other pesticides 71640 0 0.0 Benzo 3,4 pyrene 1215 1 0.1 Phosphorus 398 0 0.0 All others 25151 0 0.0 Total 198468 383 0.2
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Updated 11 July 2001
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