Thames Water Utilities Ltd
Overall Water Quality supplied by Thames Water in 2000
A total of 452,694 tests were carried out by Thames Water in 2000. Of these tests, 99.89% complied with the Regulations.
Company Information Amount of Water Supplied: 2,600 Ml/d Consumers Supplied: 7.5 million Areas of Supply: London and a large proportion of central southern England. Water Composition: 75% from rivers and reservoirs 25% from boreholes and aquifers Treatment Works: 99 Service Reservoirs: 371 Km of Mains: 31,500 Water Supply Zones: 236 Water Quality in Water Supply Zones, at Treatment Works, and in Service Reservoirs
Water supply zones
- In general, to be wholesome, water must comply with the standards set out in the Regulations. The Company carried out a total of 377,602 tests on samples taken in its 236 water supply zones. The table below includes only the parameters that breached the standard. All other parameters fully complied with the standards. Parameter meanings 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 to carry out remedial works to overcome the difficulty in meeting the individual standard.
Parameter
Total samples taken
Samples not meeting the standard
Percentage
Number of failures already covered by undertakings
Total coliforms
19,714
259
1.31
17
Faecal coliforms
19,714
10
0.05
-
Turbidity
2,537
1
0.04
-
Odour
1,354
1
0.07
-
Nitrate
2,575
4
0.16
-
Nitrite
6,135
86
1.40
-
Aluminium
2,504
1
0.04
-
Iron
2,756
7
0.25
7
Lead
1,267
5
0.39
-
PAH
1,232
28
2.27
21
Benzo3,4 pyrene
1,240
2
0.16
-
Zinc
1,267
1
0.08
-
Treatment works
Of the company’s 99 treatment works, 76 (77%) complied fully with relevant standards. Failures of the total coliforms standard at one works have resulted in consideration of enforcement action, and all other failures at treatment works were considered trivial or unlikely to recur. Differences over the last three years in the number of treatment works, and samples from treatment works, in which coliforms were detected, are not considered significant. Service reservoirs
At 368 (99%) of the Company's 371 service reservoirs, coliforms were absent from at least 95% of samples. Failures of the standard for total coliforms at two service reservoirs, and for faecal coliforms at three service reservoirs, were considered trivial or unlikely to recur as a result of action taken by the Company. Differences in the last three years in the number of service reservoirs, and samples from service reservoirs, in which coliforms were detected, are not considered significant. Company Audit and Inspection Link to expanded information (web site version)
occasions in 2000. Where relevant, report summaries are available in the ‘Business and Technical’ section of DWI’s web site under ‘Audit and Inspection’.
- The Company was inspected or audited by DWI or its appointed consultants on eight
Audit or Inspection
Date
Inspection of work being carried out on the distribution system
January, October
Annual assessment of 1999 compliance data.
April / May
Audit trails of five samples
October
Audit of plumbosolvency treatment and control programs of work
November
Follow-up of response to recommendations
December
Review of procedures for the operation and maintenance of the distribution system
December
Inspection of distribution system improvement programme progress.
Ongoing
A number of recommendations for improvements were made, and included analytical systems and health and hygiene practices when working on the distribution system. Incidents
- The Inspectorate regarded seven of the events notified during 2000 by the Company as incidents in which drinking water quality demonstrably deteriorated.
- DWI has assessed four of the incidents. Each was of short duration and the company has taken appropriate remedial action. Two recommendations were made to the Company regarding its handling of the incidents.
- During 2000, assessment was also completed for one incident which occurred in 1997, two incidents that occurred in 1998 and eight that occurred in 1999.
- Three incident assessments from 2000 remain under consideration, together with two from 1999 and one from 1998.
Nature of Incident
No. of Incidents
Assessment by DWI Completed
Areas Affected
Supply of discoloured water
2
Yes
Merton (August), Kidlington (September).
3
No
Reading (May), Swindon (December), Blunsden (December).
Failure of disinfection system
1
Yes
Dorney Water Treatment Works (May)
Microbiological contamination
1
Yes
Noke Service Reservoir (September)
Improvement Programmes
Carried Out by the Company
- Ten remedial programmes were due for full completion during 2000 and these were all completed on schedule.
- The ongoing distribution system improvement programmes due for completion in 2002, which have been implemented by the Company, have been progressing satisfactorily.
Enforcement Action
- The table below indicates areas where DWI is considering, or has taken enforcement action for, breaches of regulations.
Parameter/Area
Number
Regulation Breached
Total coliforms
1 works
Regulation 3(7)
Total coliforms
1 zone
Regulation 3(3)(c)
Nitrate
1 zone
Regulation 3(3)(c)
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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 11 July 2001
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