14 Severn Trent Water Limited
Overall water quality supplied by Severn Trent Water Limited in 2001
- A total of 273,907 tests were carried out by Severn Trent Water Limited in 2001.
- Of these tests, 99.91% complied with the Regulations.
Company Information
Amount of Water Supplied: 2,000 Ml/d
Consumers Supplied 7.36 million
Areas of Supply: The region stretches from the Humber Estuary in the north to Bristol Channel in the south, Llyn Clywedog in Wales in the west and Lincolnshire in the east
Water Composition: 65% from rivers and reservoirs
35% from boreholes and aquifers
Treatment Works: 179
Service Reservoirs: 623
Km of Mains: 41,000
Water Supply Zones: 285Water Quality in Water Supply Zones, at Treatment Works, and in Service Reservoirs
Water supply zones
- To be wholesome, water must comply with the standards set out in the Regulations. The Company carried out a total of 182,157 tests on samples taken in its 285 water supply zones. The table below includes only the parameters that breached the standard; all other parameters were fully compliant. A list of these parameters and their significance can be found at the beginning of this section.
- The last column indicates the number of failures in zones already covered by legally binding undertakings given by the Company. These undertakings required remedial work to be carried out to ensure compliance with the individual standard.
Parameter Total samples taken Samples not meeting the standard Percentage Number of failures already covered by undertakings Total coliforms 19,495 86 0.44 0 Faecal coliforms 19,495 5 0.03 0 Nitrate 5,234 1 0.02 0 Nitrite 1,462 13 0.89 0 Aluminium 1,521 3 0.20 0 Iron 5,390 36 0.67 11 Manganese 1,531 1 0.07 0 Lead 665 3 0.45 0 PAH 1,038 45 4.34 0 Benzo-3,4-pyrene 1,033 3 0.29 0 Sulphate 1,007 2 0.20 0
Treatment works
- Of the Company's 179 treatment works, 172 (96%) complied fully with the relevant standards. Failures of the standards at six works were considered trivial, or unlikely to recur as a result of remedial action taken by the Company. Enforcement action is under consideration for the remaining works. Differences over the last three years in the number of treatment works, and samples from treatment works, in which coliforms were detected were not considered significant.
Service reservoirs
- At all of the Company's 623 service reservoirs, coliforms were absent from at least 95% of samples. Failures of the faecal coliform standard at three service reservoirs were considered trivial or unlikely to recur. Differences over the last three years in the number of service reservoirs, and samples from service reservoirs, in which coliforms were detected were not considered significant.
Cryptosporidium
- The Company carried out a total of 2,935 tests on samples taken from eight sites. Very low numbers of oocysts were detected in 30 (1.02%) samples taken from eight sites. All results were well below the treatment standard and there were no associated outbreaks of cryptosporidiosis.
Company Audit and Inspection
- The Company was inspected or audited by the Inspectorate or its appointed consultants on a number of occasions during 2001. Where relevant, report summaries are available in the 'Business and Technical' section of the web site under 'Audit and Inspection'.
Audit or Inspection Date Review of procedures for operation and maintenance of the distribution network February Audit of incident notification procedures February Review of progress with the distribution system undertaking October Review of policies and procedures on contaminated land November Audit of procedures for compliance with Regulation 25 November Audit of sampling programme November Audit trails of ten samples November Inspection of one water treatment works and one service reservoir November Audit of each Cryptosporidium sampling site Various dates during the year
- Fifteen recommendations were made in respect of action required to avoid the risk of a breach of a regulatory duty. These recommendations were mainly in relation to the operation and maintenance of the distribution system and the audit trails.
- Seven recommendations for improvements were made in respect of the distribution system undertaking.
Incidents
- The Inspectorate regarded five of the events notified during 2001 by the Company as incidents. For further details on the classification of incidents see Chapter C, 'Events affecting Water Quality', in Part 3.
- Four of the incidents have been assessed by the Inspectorate. Each was of short duration and the Company has taken appropriate remedial action. Two recommendations were made to the Company mainly regarding delays in sampling and analysis.
- During the 2001 reporting period, assessment was also completed for three incidents which occurred in 2000.
- One incident assessment from 2001 remains under consideration, together with one from 2000.
Nature of incident
No.of incidents
Assessment completed by DWI
Areas affectedSupply of discoloured water
2
Yes
Stafford (June); Droitwich (April)
Gloucester (August)
Microbiological contamination
2
Yes
Stroud (July); Stourbridge (August)
Improvement Programmes
- No remedial programmes of work were due for completion in 2001.
- The ongoing distribution system improvement programme has been progressing satisfactorily. During 2000 and 2001, 886 km of mains were renovated. The Company is required to renovate a further 1,014 km of mains by December 2003.
- The Company has improvement programmes to meet the new and revised standards set down in the new Water Supply (Water Quality) Regulations 2000, which will come into force on 25 December 2003. These relate to arsenic at 29 sites, nitrate at two sites, THMs at two sites, solvents at two sites and bromate at two sites, plus additional work required to meet the new standard for lead. The Company also has programmes of work to reduce any potential risk from Cryptosporidium oocysts at 20 sites. Ten of these were completed during 2001. Progress with delivery of the remaining programmes is monitored by the Inspectorate, and has been satisfactory.
Enforcement Action
- The table below indicates areas where, in 2001, the Inspectorate considered taking enforcement action for regulatory breaches, and where an undertaking was submitted or where the Company took appropriate action.
Parameter/Area Regulation breached Location Outcome Total coliforms Reg 3(7) Strensham No 2 WTW Awaiting response Iron Reg 3(3)(c) Five zones Awaiting response
table 14.1 Severn Trent Water Limited
MICROBIOLOGICAL QUALITY OF WATER LEAVING TREATMENT WORKS2001 2000 1999 Number of water treatment works 179 164 168 Works with no sampling shortfall 176 163 168 COLIFORMS Total number of determinations 14,551 15,571 19,646 - number containing coliforms 9 15 19 - % containing coliforms <0.1 0.1 0.1 Treatment works with coliforms detected 7 11 15 - % of all works 3.9 6.7 8.9 FAECAL COLIFORMS Total number of determinations 14,551 15,571 19,646 - number containing faecal coliforms 1 0 0 - % containing faecal coliforms <0.1 0.0 0.0 Treatment works with faecal coliforms detected 1 0 0 - % of all works 0.6 0.0 0.0
table 14.2 Severn Trent Water Limited
MICROBIOLOGICAL QUALITY OF WATER IN SERVICE RESERVOIRS2001 2000 1999 Number of service reservoirs 623 614 645 Service reservoirs with no sampling shortfall 623 328* 645 COLIFORMS Total number of determinations 31,324 31,241 32,234 - number containing coliforms 45 44 38 - % containing coliforms 0.14 0.14 0.12 Service reservoirs with coliforms detected 39 37 34 Service reservoirs with coliforms detected in more than 5% of samples 0 0 1 - % of all service reservoirs 0.0 0.0 0.1 FAECAL COLIFORMS Total number of determinations 31,324 31,241 32,234 - number containing faecal coliforms 3 4 4 - % containing faecal coliforms <0.1 <0.1 <0.1 Service reservoirs with faecal coliforms detected 3 4 4 - % of all service reservoirs 0.5 0.7 0.6 * Company unable to collect samples during the fuel crisis. These shortfalls are considered trivial and unlikely to recur.
table 14.3 Severn Trent Water Limited
WATER QUALITY IN SUPPLY ZONESColumns 'CBU' show, for determinations, contraventions covered by undertakings and, for zones, the total number of zones covered by undertakings in 2001. Column 'E' shows the number of zones for which new enforcement action is under consideration as a result of contraventions of the PCV in 2001. PARAMETER DETERMINATIONS in 2001 ZONES (285 in 2001)* Total Contravening PCV Non-compliant No. % CBU CBU E Number in: 2001 2001 2000 1999 Coliforms 19,495 86 0.4 0 0 0 0 0 0 Faecal coliforms 19,495 5 0.0 0 0 0 5 5 5 Colour 1,314 0 0.0 0 0 0 0 0 0 Turbidity 4,574 3 <0.1 1 105 0 3 3 1 Odour 1,122 0 0.0 0 0 0 0 0 0 Taste 1,269 1 0.0 0 0 0 0 1 0 Hydrogen ion 1,547 0 0.0 0 0 0 0 0 0 Nitrate 5,234 1 0.0 0 0 0 1 0 0 Nitrite 1,462 13 0.9 0 0 0 2 2 1 Aluminium 1,521 3 0.2 0 0 0 3 2 0 Iron 5,390 36 0.7 11 9 5 23 20 17 Manganese 1,531 1 0.1 0 0 0 1 3 2 Lead 665 3 0.5 0 0 0 3 2 7 PAH 1,038 45 4.3 0 0 0 20 17 16 Trihalomethanes 671 0 0.0 0 0 0 0 0 0 Total pesticides 1,163 0 0.0 0 0 0 0 0 0 Other pesticides 48,867 0 0.0 0 0 0 0 0 0 Benzo-3,4-pyrene 1,033 3 0.3 0 0 0 0 0 2 Oxidisability 297 0 0.0 0 0 0 0 0 1 Phosphorous 1,004 0 0.0 0 0 0 0 0 1 Sulphate 1,007 2 0.2 0 0 0 1 0 0 All others 62,458 0 0.0 0 0 0 0 0 0 TOTAL 182,157 198 0.11 11 - - - - - *286 zones in 2000; 289 zones in 1999. [ Previous ] [ Contents ] [ Next ]
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Drinking Water Inspectorate,
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Telephone : 020 7944 5956 - Facsimile : 020 7944 5969
E-mail: dwi.enquiries@defra.gsi.gov.uk
Published 10 July 2002
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