Archive:
(for archive/historical purposes, these documents have not been updated)Index of Contents:
- Introduction
- Bacteria
- Pesticides
- Lead
- Iron and Manganese
- Cryptosporidium
- Drinking Water Quality Incidents
- Prosecution
- 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 Severn Trent Water 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.
Severn Trent continues to supply you with drinking water of a high quality. In 1999, 99.92% of more than 260,200 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, have required Severn Trent 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 Severn Trent to further improve its performance.
2. Bacteria
Whenever bacteria are found in water samples Severn Trent 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 consumers' health. The Company is being required to improve one water treatment works. Five out of 645 service reservoirs failed to meet the required standard and the Company has taken remedial action to prevent recurrence. The number of bacteriological failures at consumers' taps was only 0.3% of the samples taken. Many of these failures are likely to be due to the condition of the tap and not the water itself.
3. Pesticides
Severn Trent carried out over 8000 tests for individual pesticides during 1999 and all samples complied with the stringent standard. This reflects the significant investment in recent years to install treatment to removed 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. 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.
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 samples failing for iron and manganese decreased in 1999. A major programme of work is being carried out by Severn Trent to renovate its distribution system. The programme of improvement is ongoing with the Company being required to renovate more than 1,900 km of mains by 2003.
6. 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. Severn Trent identified that there was significant risk at 17 of its sites and it is now continuously sampling and monitoring the treated water at 12 of these sites, the other five 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.
7. Drinking Water Quality Incidents
Twenty incidents were reported to the Inspectorate during 1999. None of these was serious or put consumer's health at risk. Most incidents were transient occurrences of discoloured water. Seven incidents of discoloured water resulted from burst mains, three of these were in Derby, one in Nuneaton, one in south Warwickshire, one in Donnington Wood and one in Mountsorrel. A further seven incidents of discoloured water resulted from planned work on the distribution system, three of these were in Coventry, one in Leicester, one in Clowne, one in Darley Abbey and one in Kidderminster. Two further discoloured water incidents resulted from reservoirs emptying, due to faulty level monitors, these were Nottingham and Bakewell. One incident, in Condover, concerned the issue of advice not to use the water to nine properties after a complaint of diesel smell was linked to mains renovation work. Another incident was a disinfection failure at a Chequer House treatment works but the quality of water into supply was not affected. Advice to boil water was issued to small numbers of consumers on two occasions following the detection of indicator bacteria, once after mains renovation work in Edmondthorpe and the other occasion was after surface water ingress into Stonehall service reservoir.
8. Prosecution
During 1999 Severn Trent Water Limited pleaded guilty to supplying water unfit for human consumption in a case brought by the Inspectorate where discoloured water was supplied to the Kirkby-in-Ashfield area of Nottinghamshire in December 1997. The Company was fined £10,000.
9. Determinations in 1999
Parameter
Total
Contravening PCV No % Coliforms 20771 72 0.3 Faecal coliforms 20771 5 < 0.1 Colour 1342 0 0.0 Turbidity 1370 1 0.1 Odour 1438 0 0.0 Taste 1078 0 0.0 Hydrogen ion 2574 0 0.0 Nitrate 5209 0 0.0 Nitrite 1431 1 0.1 Aluminium 1505 0 0.0 Iron 2814 22 0.8 Manganese 1567 3 0.2 Lead 991 8 0.8 PAH 891 41 4.6 Trihalomethanes 760 0 0.0 Total pesticides 1724 0 0.0 Atrazine 1149 0 0.0 MCPA 181 0 0.0 Mecoprop 341 0 0.0 Other pesticides 6609 0 0.0 Benzo-3,4-pyrene 900 6 0.7 Phosphorus 710 1 0.1 Oxidisability 311 1 0.3 All others 80085 0 0.0 Total 156522 161 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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