24 Wessex Water Services Limited
Overall Water Quality supplied by Wessex Water Services Limited in 2001
- A total of 154,819 tests were carried out by Wessex Water Services Limited in 2001.
- Of these tests, 99.89% complied with the Regulations.
Company Information
Amount of Water Supplied: 385 Ml/d
Consumers Supplied: 1.2 million
Areas of Supply: Dorset, the majority of Somerset, and parts of Wiltshire, Hampshire and Devon
Water Composition: 20% from rivers and reservoirs
80% from boreholes and aquifers
Treatment Works: 90
Service Reservoirs: 320
Km of Mains: 10,800
Water Supply Zones: 101Water 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 99,954 tests on samples taken in its 101 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 4,837 15 0.31 0 Faecal coliforms 4,838 3 0.06 0 Turbidity 4,804 4 0.08 0 Nitrate 4,463 44 0.99 42 Nitrite 4,463 3 0.06 0 Aluminium 1,356 1 0.07 0 Iron 1,948 14 0.72 8 Manganese 2,279 3 0.13 1 PAH 585 32 5.47 0 Atrazine 487 1 0.21 0 Simazine 487 1 0.21 0 Benzo-3,4-pyrene 585 1 0.17 0 Phosphorus 186 1 0.53 0
Treatment works
- Of the Company's 90 treatment works, 82 (91%) complied fully with the relevant standards. Failures of the standards at a total of eight works were considered trivial, or unlikely to recur as a result of remedial action taken by the Company. There has been a significant decrease since 1999 in the number of samples from treatment works in which total and faecal coliforms were detected.
Service reservoirs
- At all of the Company's 320 service reservoirs, coliforms were absent from at least 95% of samples. Failures of the standard for faecal coliforms at six service reservoirs were considered trivial or unlikely to recur. Differences in 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 840 tests on samples taken from 10 sites. Very low numbers of oocysts were detected in 121 (14.40%) samples taken from seven of these 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 Audit of incident notification procedures
January Audit of arrangements for Cryptosporidium analysis
January/March/
SeptemberReview of plumbosolvency treatment and control programmes of work
October Review of progress with the distribution system undertaking
October Review of policies and procedures on contaminated land
December Audit of procedures for compliance with Regulation 25
December Audit trails of nine samples
December Inspection of one treatment works and five service reservoirs December
Review of progress with nitrate undertaking
December Audit of each Cryptosporidium sampling site
Various dates during the year
- Twenty 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 inspections of the service reservoirs and Cryptosporidium analysis. o Eight recommendations for improvements were made in relation to the plumbosolvency treatment programme.
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.
- Three 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 procedures.
- One incident assessment from 2001 remains under consideration.
Nature of incident
No.of incidents
Assessment completed by DWI
Areas affectedSupply of discoloured water
2
Yes
Taunton (March)
No
Weymouth (September)
Microbiological contamination of
service reservoirs
1
Yes
Woodford SR (August)
Other incidents not affecting water quality
2
Yes
Monkton Farleigh (September); Salisbury (September)
Improvement Programmes
- No remedial programmes of work were due for completion during 2001.
- The ongoing distribution system improvement programme due for completion in 2005 has been progressing satisfactorily. In the last two years, 206 km of mains have been renovated. The Company is required to rehabilitate a further 437 km of mains by 2005.
- 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 one site, plus additional work required to meet the new standard for lead. The Company also has programmes of work to further reduce any risk from Cryptosporidium oocysts at 19 sites. Progress with delivery of the 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 Nitrate Regulation 3(3)(c) Black Lane zone; Clarendon zone;
Millborne
St Andrew zone;
Fovant zonesUndertakings received Iron Regulation 3(3)(c) Salisbury Zone Undertakings received
table 24.1 Wessex WaterServices Limited
MICROBIOLOGICAL QUALITY OF WATER LEAVING TREATMENT WORKS2001 2000 1999 Number of water treatment works 90 93 96 Works with no sampling shortfall 90 93 96 COLIFORMS Total number of determinations 10,528 10,735 11,142 - number containing coliforms 8 8 19 - % containing coliforms <0.1 <0.1 0.2 Treatment works with coliforms detected 8 7 15 - % of all works 8.9 8.0 15.6 FAECAL COLIFORMS Total number of determinations 10,530 10,743 11,164 - number containing faecal coliforms 1 2 9 - % containing faecal coliforms <0.1 <0.1 <0.1 Treatment works with faecal coliforms detected 1 2 7 - % of all works 1.1 2.2 7.3
table 24.2 Wessex Water Services Limited
MICROBIOLOGICAL QUALITY OF WATER IN SERVICE RESERVOIRS2001 2000 1999 Number of service reservoirs 320 325 325 Service reservoirs with no sampling shortfall 320 325 325 COLIFORMS Total number of determinations 16,903 17,129 17,117 - number containing coliforms 33 25 33 - % containing coliforms 0.2 0.2 0.2 Service reservoirs with coliforms detected 29 19 27 Service reservoirs with coliforms detected in more than 5% of samples 0 2 0 - % of all service reservoirs 0.0 0.6 0.0 FAECAL COLIFORMS Total number of determinations 16,904 17,134 17,133 - number containing faecal coliforms 7 5 9 - % containing faecal coliforms <0.1 <0.1 <0.1 Service reservoirs with faecal coliforms detected 6 5 9 - % of all service reservoirs 1.9 1.5 3.0
table 24.3 Wessex Water Services 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 (101 in 2001)* Total Contravening PCV Non-compliant No. % CBU CBU E Number in: 2001 2001 2000 1999 Coliforms 4,837 15 0.3 0 0 0 0 0 0 Faecal coliforms 4,838 3 0.1 0 0 0 3 1 2 Colour 1,641 0 0.0 0 0 0 0 0 0 Turbidity 4,804 4 0.1 0 0 0 4 1 4 Odour 263 0 0.0 0 0 0 0 0 0 Taste 266 0 0.0 0 0 0 0 0 0 Hydrogen ion 4,806 0 0.0 0 0 0 0 0 1 Nitrate 4,463 44 1.0 42 7 3 6 2 1 Nitrite 4,463 3 0.1 0 0 0 3 0 1 Aluminium 1,356 1 0.1 0 0 0 1 0 1 Iron 1,948 14 0.7 8 40 1 10 11 11 Manganese 2,279 3 0.1 1 1 0 3 3 2 Lead 751 0 0.0 0 0 0 0 0 2 PAH 585 32 5.5 0 0 0 18 12 30 Trihalomethanes 370 0 0.0 0 0 0 0 0 0 Total pesticides 748 0 0.0 0 0 0 0 0 0 Atrazine 487 1 0.2 0 0 0 1 0 1 Diuron 290 0 0.0 0 0 0 0 0 1 Simazine 487 1 0.2 0 0 0 1 0 1 Other pesticides 4,038 0 0 0 0 0 0 0 0 Benzo 3,4 Pyrene 585 1 0.2 0 0 0 0 0 0 Phosphor 186 1 0.5 0 0 0 1 0 0 All others 55,463 0 0.0 0 0 0 0 0 0 TOTAL 99,954 123 0.12 51 - - - - - *103 zones in 2000; 108 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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