Chief Inspector's Report 2002
21 Thames Water Utilities Limited
| Overall Water Quality supplied by Thames Water Utilities Limited in 2002 | |||||||||||||||||||||||
|
|||||||||||||||||||||||
|
|
||||||||||||||||||||||
Water Quality at Treatment Works, in Service Reservoirs and in Water Supply Zones
To be wholesome, water must comply with the standards for the parameters set out in the Water Supply (Water Quality) Regulations 1989. In 2002, the Company carried out a total of 542,555 tests on samples taken at water treatment works, from service reservoirs and in water supply zones and of these, 99.92% complied with the relevant water quality standards set down in the Regulations. A list of the parameters, the relevant standards and their significance can be found at the beginning of this section.
Water Quality leaving Treatment works
2002 |
2001 |
2000 |
||
| Number of water treatment works | 101 |
101 |
99 |
|
| COLIFORMS | ||||
| Total number of tests | 15,434 |
16,046 |
18,816 |
|
| - | number containing coliforms | 9 |
18 |
32 |
| - | % containing coliforms | 0.06% |
0.11% |
0.17% |
| Treatment works with coliforms detected | 9 |
16 |
23 |
|
| - | % of all works with coliforms detected | 8.91% |
15.84% |
23.23% |
| FAECAL COLIFORMS | ||||
| Total number of tests | 15,437 |
16,046 |
18,816 |
|
| - | number containing faecal coliforms | 0 |
1 |
1 |
| - | % containing faecal coliforms | 0.00% |
0.01% |
0.01% |
| Treatment works with faecal coliforms detected | 0 |
1 |
1 |
|
| - | % of all works with faecal coliforms detected | 0.00% |
0.99% |
1.01% |
Failures of the coliform standard at nine works in 2002 were considered trivial. There were no failures of the faecal coliform standard. Differences over the last three years in the number of treatment works, and in the number of tests carried out on samples from treatment works, in which coliforms or faecal coliforms were detected were not considered significant.
In 2002, 6,086 regulatory samples for Cryptosporidium were taken at 20 sites. Very low numbers of oocysts were detected in 122 samples from 13 sites. All results were well below the treatment standard and there were no reported outbreaks of cryptosporidiosis.
Water Quality in Service Reservoirs
2002 |
2001 |
2000 |
||
| Number of service reservoirs | 367 |
372 |
371 |
|
| COLIFORMS | ||||
| Total number of tests | 19,409 |
19,182 |
18,730 |
|
| - | number containing coliforms | 26 |
37 |
57 |
| - | % containing coliforms | 0.13% |
0.19% |
0.30% |
| Service reservoirs with coliforms detected | 20 |
33 |
50 |
|
| Service reservoirs with coliforms detected | 2 |
0 |
3 |
|
| in more than 5% of tests | ||||
| - | % of all service reservoirs with coliforms detected | 0.54% |
0.00% |
0.81% |
| FAECAL COLIFORMS | ||||
| Total number of tests | 19,412 |
19,182 |
18,730 |
|
| - | number containing faecal coliforms | 2 |
2 |
3 |
| - | % containing faecal coliforms | 0.01% |
0.01% |
0.02% |
| Service reservoirs with faecal coliforms detected | 2 |
2 |
3 |
|
| - | % of all service reservoirs with faecal coliforms detected | 0.54% |
0.54% |
0.81% |
There were failures of the coliform standard at two service reservoirs. There was also a failure of the faecal coliform standard at one of these reservoirs. However, the Company has taken action to prevent the failures recurring. There has been a significant decrease over the last three years in the number of service reservoirs and in the number of tests carried out on samples taken from service reservoirs in which total coliforms were detected. All other differences were not considered significant.
Water Quality in Water Supply Zones
The table below shows the data for the key parameters and any other parameters where there was a failure of the standard. All other parameters were fully compliant.
| Parameter | Total number of tests |
Tests not meeting the prescribed concentration or value |
Number of failures covered by Undertakings |
Number of zones not complying with the standards |
|||
No |
% |
2002 |
2001 |
2000 |
|||
| Coliforms | 20,675 |
213 |
1.03 |
2 |
3 |
2 |
4 |
| Faecal coliforms | 20,682 |
11 |
0.05 |
0 |
11 |
12 |
9 |
| Colour | 2,247 |
0 |
0.00 |
0 |
0 |
0 |
0 |
| Turbidity | 2,284 |
0 |
0.00 |
0 |
0 |
0 |
1 |
| Odour | 1,132 |
1 |
0.09 |
0 |
1 |
1 |
1 |
| Taste | 1,110 |
0 |
0.00 |
0 |
0 |
0 |
0 |
| Hydrogen ion | 3,268 |
0 |
0.00 |
0 |
0 |
0 |
0 |
| Nitrate | 2,350 |
5 |
0.21 |
3 |
4 |
3 |
2 |
| Nitrite | 2,795 |
94 |
3.36 |
0 |
31 |
24 |
40 |
| Aluminium | 2,358 |
2 |
0.08 |
0 |
2 |
1 |
1 |
| Iron | 2,957 |
6 |
0.20 |
5 |
4 |
9 |
6 |
| Manganese | 2,290 |
0 |
0.00 |
0 |
0 |
1 |
0 |
| Lead | 1,415 |
7 |
0.49 |
0 |
6 |
6 |
4 |
| PAH | 1,226 |
28 |
2.28 |
0 |
19 |
8 |
15 |
| Trihalomethanes | 1,038 |
0 |
0.00 |
0 |
0 |
0 |
0 |
| Total pesticides | 27,391 |
0 |
0.00 |
0 |
0 |
0 |
0 |
| Diuron | 16,792 |
0 |
0.00 |
0 |
0 |
6 |
0 |
| Other pesticides | 311,480 |
0 |
0.00 |
0 |
0 |
0 |
0 |
| Benzo 3.4 Pyrene | 1,226 |
2 |
0.16 |
0 |
1 |
0 |
1 |
| Phosphorus | 257 |
0 |
0.00 |
0 |
0 |
1 |
0 |
| Tetracholoethene | 1,038 |
1 |
0.10 |
0 |
0 |
0 |
0 |
| Zinc | 1,411 |
1 |
0.07 |
0 |
1 |
0 |
1 |
| All others | 39,355 |
0 |
0.00 |
0 |
0 |
0 |
0 |
| TOTAL | 466,777 |
371 |
0.08% |
10 |
|||
| 244 zones in 2002, 244 zones in 2001 and 236 zones in 2000 | |||||||
The fifth column indicates the number of failures in zones already covered by legally binding undertakings given by the Company. These undertakings require remedial work to be carried out to ensure compliance with the individual standard.
The New Regulations
In 2002, the Company carried out monitoring for the six new parametric values set down in the new Water Supply (Water Quality) Regulations 2000. These Regulations come into force on 25 December 2003. The results are shown in the table below.
| Parameter | Total number of tests |
New standard |
Tests not meeting the new standard |
| Benzene | 465 |
1.0 µg/l |
0 |
| Bromate | 482 |
10.0 µg/l |
0 |
| 1,2 dichloroethane | 465 |
3.0 µg/l |
0 |
| Nitrite (ex-water treatment works) | 488 |
0.1 mg/l |
0 |
| Clostridium perfringens | 108 |
0/100 ml |
0 |
| Enterococci | 1,145 |
0/100 ml |
4 |
Compliance data for 2002 has also been analysed against the revised standards and the results are shown in the following table.
| Parameter | Total number or tests |
Current Standard |
Number of tests not meeting current standard |
Revised Standard |
Number of tests not meeting revised standard |
|||
| Antimony | 251 |
10.0 µg/l |
0 |
5.0 µg/l |
0 |
|||
| Arsenic | 251 |
50.0 µg/l |
0 |
10.0 µg/l |
0 |
|||
| Boron | 251 |
2.0 mg/l |
0 |
1.0 mg/l |
0 |
|||
| Copper | 1,412 |
3.0 mg/l |
0 |
2.0 mg/l |
2 |
|||
| Lead | 1,415 |
50.0 µg/l |
7 |
25.0 µg/l1 |
32 |
|||
10.0 µg/l2 |
118 |
|||||||
| Nickel | 251 |
50.0 µg/l |
0 |
20.0 µg/l |
0 |
|||
| Nitrite (at consumers' taps) | 2,795 |
0.1 mg/l |
94 |
0.5 mg/l |
0 |
|||
| PAH | 1,226 |
0.2 µg/l |
28 |
0.1 µg/l |
1 |
|||
| Tetrachloroethene | 1,037 |
30.0 µg/l |
|
10.0 µg/l
|
1
|
|||
| Trichloroethene | 1,037 |
10.0 µg/l |
Details of the new and revised standards, and the reasons for the revisions where applicable, can be found in chapter J "New Regulations and Associated Programmes of Work".
1 From 25.12.03
2 From 25.12.13
Company Audit and Inspection
The Company was inspected or audited by the Inspectorate or its appointed consultants on a number of occasions during 2002. Where relevant, report summaries are available in the 'Business and Technical' section of the Inspectorate's web site under 'Audit and Inspection'.
| Audit or Inspection | Date |
| Audit of regulatory Cryptosporidium monitoring sites | Various dates |
| Audit of regulatory Cryptosporidium samplers | January 2002 |
| Unannounced Inspection of laboratory analysing for Cryptosporidium | February 2002 |
| Audit of progress with regulatory programmes of work | March 2002 |
| Review of the distribution system undertaking | August 2002 |
| Audit trails of 15 test results | September 2002 |
| Audit of sampling arrangements | September 2002 |
| Inspection of one water treatment works and one service reservoir | October and |
| Audit of response to selected consumer complaints | November 2002 |
| Review of plumbosolvency treatment and control programmes of work | November 2002 |
A number of recommendations were made in respect of action required to avoid the risk of a breach of a regulatory duty. These recommendations were in relation to the audit trails, the operation of treatment works and service reservoirs, the programmes of work and plumbosolvency treatment for lead.
Incidents
The Inspectorate regarded seven of the events notified during 2002 by the Company as incidents. For further details on the classification of incidents, see chapter C "Events affecting Water Quality" in Part 3.
All of the incidents have been assessed by the Inspectorate. Each was of short duration and Thames Water has taken appropriate remedial action. A number of recommendations were made regarding procedures and the operation of valves.
During the 2002 reporting period, assessment was also completed for one incident which occurred in 2001.
| Nature of incident | No. of incidents |
Assessment completed |
Area affected |
Population potentially affected |
| Supply of discoloured water | 4 |
Yes |
Edmonton (March) |
1,250 |
Yes |
Parts of Swindon (April) |
1,500 |
||
Yes |
Parts of Reading (April) |
1,500 |
||
Yes |
Parts of Bromley (January) |
130 |
||
| Visual/Chemical contamination of supplies | 2 |
Yes |
Winnersh (April) |
2 |
Yes |
Parts of Croydon (October) |
125 |
||
| Failure of disinfection | 1 |
Yes |
Parts of Gloucestershire |
7,800 |
around Mickleton and |
||||
Paxford (July) |
Enforcement Action
The table below indicates areas where, in 2002, 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 |
| Lead | 3(3)(c) | City of London water supply zone |
Remedial action taken |
| Iron, manganese and turbidity |
3(3)(c) | Spencer Wood & Winnersh water supply zones |
Remedial action taken |
Undertakings and other Improvement Programmes
Water treatment works and service reservoirs
Two undertakings were due for completion during 2002. These were to carry out improvements in Brixton water supply zone for total coliforms and install treatment at Worsham for nitrate. The programmes were completed on schedule.
One Regulation 41 programme of work to meet the new and revised standards set down in the new Water Supply (Water Quality) Regulations 2000 was due for completion in 2002. This was to install treatment at Southfleet to remove nitrate. The programme was completed on schedule.
Four statements of intent to reduce the risk of Cryptosporidium breaching the treatment standards were due for completion during 2002. One programme was completed on schedule. One programme was not completed because the Company had reviewed the risk and determined action was not required. The classification of the other two sites remains under consideration.
No other improvement programmes were due for completion during 2002.
Distribution
The distribution system undertaking was completed during 2002. During 2002, 90.4 km of mains have been renovated.
Lead
The Company has a Regulation 41 programme of work to meet the revised standard for lead set down in the new Water Supply (Water Quality) Regulations 2000, which will come into force on 25 December 2003. Progress with the delivery of the programme is monitored by the Inspectorate and has been satisfactory.
