Part 2
Individual Water Company Performance in 2002
- A section on each of the four water companies describing their
overall performance for the year and the extent to which they
complied with the requirements of the Water Supply (Water Quality)
Regulations 1989 and all its amendments.
|
General
- Each individual company section contains the following where appropriate:
- A general statement about overall water quality in 2002
- Company Information
- Water Quality in Water Supply Zones, at Treatment Works,
and in Service Reservoirs
- Company Audit and Inspection
- Incidents
- Prosecutions (if any)
- Improvement Programmes Carried Out by the Company
- Enforcement Action
Comparison of Water Quality
The information given in the sections about water quality in each company's
area indicates the extent to which the company has or has not complied
with the requirements of the Water Quality Regulations. It should not
be used simplistically to make comparisons of the overall quality of
drinking water between different company areas or of the relative efficiency
of different companies.
The quality of drinking water varies within and between company areas,
and depends not only on the treatment processes employed and the condition
of the distribution system, but also on the nature of the source from
which the water is obtained. For example, water from a borehole in a
chalk aquifer would normally be of better microbiological quality than
water from many other types of source. In addition, it should be noted
that for all parameters, the greater the number of samples taken, the
more likely it is that breaches of the standards will be detected.
This is not to say that meaningful comparisons of water company performance
cannot be made. The Inspectorate has developed statistical procedures
for categorising water companies on the basis of quality of water supplied
and on efficiency of managing treatment and distribution, and results
obtained using these procedures are presented in Part 1 of this Report.
Microbiological Water Quality
The detection of coliforms in a sample does not mean that it is likely
that the water supply will cause illness but is indicative of potential
contamination that must be investigated immediately. The Regulations
require 100% compliance with water quality standards for total and faecal
coliforms at water treatment works, and for faecal coliforms at service
reservoirs and in zones. They allow no more than 5% of samples taken
in any year from service reservoirs or in zones to contain total coliforms
in order to achieve compliance. Breaches may result in enforcement action
unless the company has taken remedial action to prevent recurrence.
Breach of Standards
Reference to parameters that breached the standards in one or more
samples does not mean that any of these breaches resulted in harm to
the health of consumers. Only some of the parameters are of health significance
and their standards are generally set with a wide margin of safety.
The other parameters are of aesthetic significance, with standards set
generally well below the level at which water would become unacceptable
to consumers, and the breaching of those standards doesn't mean that
the water is unfit to drink.
However, breach of a standard, even for only one parameter and in only
one sample out of the large number taken from each water supply zone
in the course of the year, is of significance because the water supplied
at the time the sample was taken cannot be regarded as wholesome. When
considered in the light of other results of monitoring, it may mean
that some action is required in order to meet the high standards specified
in the Regulations.
Consideration of Enforcement Action
For 2002, the Inspectorate has generally regarded a breach of a standard
for an individual (non-microbiological) parameter on a single occasion
in a water supply zone as trivial, provided that ten or more samples
have been taken in that zone or, if a smaller number has been taken,
provided that there was not a corresponding breach in 2001. In other
cases, the Inspectorate has taken into account the number of determinations
carried out and the number and the extent of the breaches in deciding
whether the breaches were trivial or not.
The Inspectorate considers enforcement in all cases where the breaches
are not regarded as trivial, unless the company has already taken remedial
action to prevent a breach recurring or the Inspectorate judges that
the breach is in any case unlikely to recur. A breach of the coliform
standard at a consumer's tap is also regarded as trivial if the company
can demonstrate beyond reasonable doubt that the breach arose solely
as a result of the condition of the consumer's plumbing or tap from
which samples were taken.
Quality Standards Table and Glossary
As an aid to understanding the company sections, definitions for all
the individual parameters and many of the scientific terms used, can
be found in the following Quality Standards Table or in the Glossary
in the Annexes of this Report. These definitions apply to current regulations.
For changes to be introduced under the new regulations see Chapter J,
'New Regulations and Associated Programme of Work', in Part 2
Substance
Microbiological
parameters |
Description |
Standard
Amount
Allowed |
| Faecal coliforms, faecal streptococci,
Clostridium perfringens |
|
| Faecal coliforms, faecal streptococci and Clostridium perfringens
are present in the gut of all warm-blooded animals. Their
presence in water supplies indicates a need to take immediate
action to remove the source of faecal pollution. Individual
samples and tests are carried out for each organism. These
organisms are controlled through the disinfection of water. |
|
|
| |
| The coliform group of organisms is widely distributed in
the environment, for example through human and animal activity
and through vegetable matter. Their presence in water supplies
indicates a need to investigate the source of contamination.
Coliform numbers are controlled through the disinfection of
water. |
|
|
| |
| The concentration of this parameter is an indication of
the natural hardness and pH of the water. |
|
|
| |
| Occurs naturally in some source waters. This aluminium is
removed during the water treatment processes (coagulation
and filtration) Aluminium sulphate can be used as a water
treatment chemical to remove cloudiness. |
|
|
| |
| Ammonium salts are naturally present in trace amounts in
most water sources. They decompose during disinfection. |
|
|
| |
| Antimony is toxic and is not present in water sources. Trace
concentrations in drinking water, which are not of any significance
to health, can be derived from brass fittings and from solders. |
|
|
| |
| Naturally present at trace levels in a very few groundwater
sources. Arsenic is toxic and when present it is removed by
specialist water treatment processes. |
|
|
| |
| Occurs naturally in trace concentrations in some water sources.
The concentrations present in water do not present any risk
to health. |
|
|
| |
| Boron in water sources comes from the residues of detergent
formulations that are present in treated sewage effluents.
The concentrations present in water do not present any risk
to health. |
|
|
| |
| Cadmium is toxic and present at trace levels in a very few
groundwater sources. When present it is removed by specialist
water treatment processes. |
|
|
| |
| Occurs naturally in all water sources and along with magnesium
is responsible for the hardness of water, which causes scale
in kettles and hot water systems. The concentrations present
in water do not present any risk to health. |
|
|
| |
| In association with sodium, chloride occurs naturally as
a very dilute salt in all water sources and is not removed
during water treatment. The concentrations present in water
do not present any risk to health. |
|
|
| |
| Chlorine gas is used as a disinfectant in water treatment.
It destroys bacteria derived from animal wastes and sewage
effluents. |
|
|
| |
| Not present in water sources and is not found in drinking
water. |
|
|
| |
| Colour occurs naturally in water from upland sources. Colour
is removed during the water treatment processes (coagulation
and filtration). |
|
|
| |
| Electrical conductivity is a measure of the amount of natural
dissolved inorganic substances in source water. It is used
to assist treatment control. |
|
|
| |
| Traces of copper, which are not significant to health, occur
naturally in many water sources and significant concentrations
may occur at consumers' taps as a consequence of copper pipes.
The concentrations present in water do not present any risk
to health. |
|
|
| |
| Cyanide is toxic and is not present in water sources. It
is not found in drinking water. |
|
|
| |
| Traces of fluoride occur naturally in many water sources,
particularly groundwater. It is not removed by conventional
water treatment and some water companies artificially fluoridate
water supplies as a protection against tooth decay. See the
web site for more information on fluoridation of drinking
water. |
|
|
| |
| Hydrocarbons include petroleum, mineral oils and other associated
products of the petro-chemical industry. Very occasionally
localised contamination of groundwater may occur or there
may be permeation of plastic water pipes via contaminated
ground conditions. The concentration present in water do not
present any risk to health but might give rise to taste/odour. |
|
|
| |
|
|
| |
| Present naturally in many water sources. This iron is removed
during water treatment. Iron in water supplies may also be
derived from corrosion of iron mains, but any concentrations
present in water do not present any risk to health. Iron compounds
are used as water treatment to remove cloudiness. |
|
|
| |
| Not normally present in water sources but may be present
at consumers' taps if lead pipes are used. If the water supply
tends to dissolve lead, water companies must protect the health
of consumers and treat the water to reduce exposure. |
|
|
| |
| Occurs naturally in all water sources and along with calcium
is responsible for the hardness of water, which causes scale
in kettles and hot water systems. The concentrations present
in water do not present any risk to health. |
|
|
| |
| Present naturally in many water sources and is removed during
water treatment. |
|
|
| |
| Mercury is toxic and is not present in water sources or
drinking water. |
|
|
| |
| Not found in water sources. Traces found in drinking water
may emanate from protective coatings on taps and fittings.
These traces do not present a risk to health. |
|
|
| |
| Present naturally in all source waters, although higher
concentrations can be caused by use of fertilisers. Where
necessary, nitrate levels are reduced during water treatment
(ion exchange or blending with low nitrate water). See the
web site for information on health implications and control
measures. |
|
|
| |
| Traces of nitrite are produced when chlorine and ammonia
are used in the disinfection process. Levels are minimised
through careful operation of the disinfection process. See
the web site for more information (under 'nitrate'). |
|
|
| |
| The oxidisability of the water provides a measure of its
organic content. This is an alternative measure of TOC. |
|
|
| |
| Polycyclic aromatic hydrocarbons are present in coal tar
linings, which were used to protect water mains before 1970.
Traces of PAH, at concentrations that are not of significance
to health, are present in tap water if the original coal tar
lining is still present. |
|
|
| |
|
|
| |
| Many water sources contain traces of toxic pesticide residues
as a result of agricultural and non-agricultural uses of pesticides
on crops, and for weed control. Where necessary, water companies
have installed special treatment processes to protect public
health by removing pesticides (activated carbon and ozone
processes). See the web site for information on pesticide
removal. |
|
|
| |
| pH value or hydrogen ion concentration gives an indication
of the degree of acidity of the water. pH7 is neutral; values
below 7 indicate acidic characteristics and values greater
than 7 indicate basic characteristics. A low pH value may
result in pipe corrosion. An alkali which is not harmful to
health may be added before supply so that corrosion is minimised. |
|
|
| |
| Traces of phosphorus salts occur naturally in many water
sources and high concentrations are associated with treated
sewage effluents and agricultural fertilisers. Phosphates
are also used in water treatment as a health protection measure
to reduce lead content that may come from consumers' pipes.
The concentrations present in water do not present any risk
to health. |
|
|
| |
| This occurs naturally in all water sources and is not removed
during water treatment. The concentrations present in water
do not present any risk to health. |
|
|
| Qualitative odour and taste |
|
| Odour and taste occur naturally, particularly in surface
water sources during the summer. On site tests indicate any
potential odour and taste. The organics causing the odour
and taste are removed during the water treatment process (activated
carbon or ozone). |
|
|
| Quantitative odour and taste |
|
| A formal method is undertaken in the laboratory to measure
odour and taste in water. Individual tests are carried out,
and any imperfections are removed during the treatment process
as described above. |
|
| Dilution No of 3 at 25 °C |
|
| |
| Selenium is toxic and is not present in water sources and
is not found in drinking water. |
|
|
| |
| This is not present in source waters and is not normally
found in public drinking water. Silver may be used as a disinfectant
for small private supplies. |
|
|
| |
| In association with chloride, sodium occurs naturally as
a very dilute salt in all water sources and is not removed
during water treatment. The concentrations present in water
do not present any risk to health. |
|
|
| |
| This occurs naturally in all source waters and is not removed
during water treatment. The concentrations present in unsoftened
water do not present any risk to health. |
|
|
| |
| Surfactants in water sources come from the residues of detergent
formulations that are present in treated sewage effluents.
They are removed during treatment. |
|
|
| |
| The temperature of surface waters varies according to the
season. Groundwater has a much smaller variation in temperature
range. |
|
|
| |
|
|
| |
|
|
| |
| These solvents can be present at low concentrations in groundwater
under industrial areas. Where necessary, specialist treatment
is used to protect public health by removing solvents from
drinking water. |
|
|
| |
| THMs are formed during the disinfection process by reaction
between chlorine and mainly naturally-occurring organic substances.
Treatment processes are controlled to minimise their production.
See the web site for information on the control of THMs. |
|
|
| |
| All source waters are naturally cloudy occasionally. Turbidity
is a quantitative measure of cloudiness, and levels are controlled
by the treatment processes. |
|
| 4 Formazin Turbidity Units |
|
| |
| This is a measure of the naturally-occurring minerals in
water. |
|
|
| |
| This represents the concentration of both naturally-occurring
calcium and magnesium in the source water. Hard water can
cause scale formation in kettles and hot water systems. The
concentrations present in water do not present any risk to
health. |
|
|
| Total organic carbon (TOC) |
|
| TOC represents the total amount of organic matter present
in the water. The concentrations present in water do not present
any risk to health. |
|
|
| |
| Significant concentrations of zinc in water are only found
in premises served by galvanised iron service pipes. Traces
of zinc which are not of significance to health may emanate
from solders. |
|
|
Water and Sewerage Companies and Water-Only
Companies of England and Wales
1. Anglian Water Services Limited (p.47)
2. Bournemouth and West Hampshire Water
Plc (p.54)
3. Bristol Water Plc (p.59)
4. Cambridge Water company (p.65)
5. Cholderton and District Water Company Limited
(p.71)
6. Dee Valley Water Plc (p.75)
7. Dwr Cymru Cyfyngedig (p.80)
8. Essex and Suffolk Water Plc (p.87)
9. Folkestone and Dover Water Service Limited
(p.93)
10. Hartlepool Water Plc (p.98)
11. Mid Kent Water Plc (p.103)
12. Northumbrian Water Limited (p.108)
13. Portsmouth Water Plc (p.114)
14. Severn Trent Water Limited (p.119)
15. South East Water Plc (p.125)
16. South Staffordshire Water Plc (p.131)
17. South West Water Limited (p.136)
18. Southern Water Limited (p.142)
19. Sutton and East Surrey Plc (p.148)
20. Tendring Hundred Water Services
Limited (p.154)
21. Thames Water Utilities Limited (p.159)
22. Three Valleys Water Plc (p.165)
23. United Utilities Water PLC (p.171)
24. Wessex Water Services Limited (p.178)
25. Yorkshire Water Services Limited (p.184)
Inset Appointment
26. Albion Water Limited (p.191) |
 |
|
