Drinking water 2010 - DWI, UKdwi.defra.gov.uk/about/annual-report/2010/thames.pdf · Drinking water 2010 4 Introduction to the report for the Thames region Drinking water 2010 is

Drinking Water Inspectorate | 55, Whitehall | London | SW1A 2EY | Tel: 020 7270 3370

http://www.dwi.gov.uk

Drinking Water Inspectorate | Ergon House, Horseferry Road | London | SW1P 2AL | Tel: 030 0068 6400

www.dwi.gov.uk

PB13480

Drinking water2010Public water supplies in the Thames region of EnglandJuly 2011A report by the Chief Inspector of Drinking Water

Drinking w

ater 2010 P

ublic water supplies in the Tham

es region of England

Thames reg ion

1

Drinking water 2010

Thames region of England

Dr ink ing wate r 2010

2

Publ ished by

Dr ink ing W ater Inspectorate

Area 4a

Ergon House

Horseferry Road

London

SW 1P 2AL

Tel: 030 0068 6400

Website: www.dwi.gov.uk

© Crown Copyr ight 2011

ISBN: 978-1-905852-54-3

Copyr ight in the typographical arrangement and des ign rests wi th the Crown.

This publ icat ion (exc luding the logo) may be reproduced f ree of charge in any

format or medium provided that i t is reproduced accurate ly and not used in a

misleading context . The mater ia l must be acknowledged as Crown copyr ight wi th

the t i t le and source of the publ icat ion spec if ied.

Thames reg ion

3

Contents

Introduction 4

Water supply arrangements 8

Drinking water qual ity test ing 10

Drinking water qual ity results 11

Drinking water qual ity events 33

Technical audit act iv ity 38

Publ ic conf idence in drinking water qual ity 40

Planned drinking water quality improvements 44

Annex 1: Further sources of information 49

Annex 2: Glossary and descript ion o f standards 50

Annex 3: Drinking water qual ity events in the region 63

Annex 4: Planned drinking water quality improvements 72

Annex 5: Compet it ion in the water industry 74

Annex 6: Water company indices 76

Drink ing Water 2010 is the annua l repor t o f the Dr ink ing Water Inspecto rate and

compr ises reports cover ing publ ic and pr ivate water suppl ies .

Publ ic suppl ies – Th is par t descr ibes dr ink ing water qual i ty in the Thames reg ion. The

Inspectorate a lso publ ishes a ser ies of companion reports f o r o ther reg ions of England

(Centra l , Easte rn, Northern, Southern and Western reg ions) and a separate report for

Wales.

Pr ivate suppl ies – A summary of in format ion on pr ivate water suppl ies i s reported fo r

England and Wales.

Al l par ts are avai lab le on the Inspectorate ’s websi te www.dwi .gov.uk and on the CD

accompanying th is repor t a long wi th separate summary data for water company

sampl ing programmes.


4

Introduction to the report for the Thames region

Drinking water 2010 is publ ished as a ser ies of nine reports, seven of

which cover publ ic water suppl ies and two descr ibe pr ivate water suppl ies

in England and Wales. Each report presents information about drinking

water qual ity in a form that meets the needs of those who have an interest

in the quality and safe management of drinking water suppl ies f rom the

consumer ’s perspect ive, namely the local authorit ies and the regional

committees of the Consumer Counci l for Water.

This report describes the key facts about the quality of public drinking

water suppl ies in the Thames region, which is served by f ive water

companies (Sutton and East Surrey Water, Thames Water and Veolia

Water Central , and two inset appointees; SSE Water and Independent

Water Networks Ltd) del iver ing water suppl ies to over 12 mil l ion

consumers.

Thames reg ion

5

The results of test ing in 2010 demonstrated that the overal l qual ity of

drinking water in the Thames region was excellent. The f igure for

compliance with dr inking water standards at consumers’ taps was 99.98%,

up from the f igure of 99.97% reported in 2009 and above the industry

overall average.

When the Thames region is judged by the Inspectorate’s four indices of

water qual ity performance, which look in turn at water treatment

(compris ing process control and disinfect ion) , service reservoir integrity

and network maintenance, the main change in 2010 was an improvement in

the f igure for disinfect ion (99.98%). When compared to last year, process

control (>99.99%), reservoir integrity (99.96%) and network maintenance

(99.92%) al l remained the same. The reservoir integrity f igure equalled the

industry average and the other three indices were above the average for

the industry. Individual water company f igures are reported in Annex 6 .

Across the region there were fewer operational events affect ing water

quality overal l (51 compared to 64 in 2009), Just over one -quarter (14)

were of a type that necessitated a detai led investigation by an inspector.

This represents an increase in the proport ion of events requir ing closer

scrut iny. One event, of a more unusual nature, was classif ied as ‘ser ious’

and necessitated the deployment of a considerable amount of Inspectorate

resource. The event resulted in water with an object ionable taste and

odour being supplied to around two mill ion consumers in North London.

The taste and odour was due to chemicals in the raw water reservoir

source (or iginat ing f rom the River Lee) which is managed by Thames

Water. In addit ion to being used as the source of water for its own works,

the reservoir water also provides a bulk supply of wa ter to a works

operated by Essex and Suffolk Water. The chemicals were present at

levels which exceeded the taste and odour threshold and were not

removed by the treatment in place. This event is descr ibed in more detai l

in the Drinking water qual ity events sect ion . In terms of the nature of the

events reported on this year, a common theme was problems relat ing to

dis infect ion. Detai led f indings regarding al l the signif icant events in 2010

can be found in Annex 3 . In 2010, r isk-based technical audit highl ighted

analyt ical malpract ice at a laboratory operated by Severn Trent Services

affect ing eight water companies and six regions (see the Technical audit

activ ity sect ion for further detai ls).

The long-term trend in publ ic conf idence in dr inking water quality

continues to improve in the Thames region. The number of people across

the region expressing concern about the quality of their tap water

(appearance, taste and i l lness) has continued to fal l. By comparison to

other regions in England, the Thames region n ow has the lowest contact

rate (0.9 per 1,000 populat ion). However, in 2010 , previous progress in

reducing white water events in the region stalled. The Thames region


6

exhibits relat ively low contact numbers for black, brown or orange water

and these now stand at around 2,300, down from 3,000 in 2009. However ,

more consumers were suff icient ly dissatisf ied with the way a company

dealt with their complaint that they raised the matter direct ly with the

Inspectorate (25 compared to eight in 2009). This marked change for the

worse was due almost exclusively to the aforementioned ser ious taste and

odour event in the north-east area of London and it serves to i l lustrate how

such events can erode publ ic conf idence (see case studies in the Public

confidence in drinking water qual ity section in this report and the Eastern

region report).

This year sees the 20-year anniversary of the implementat ion of the

European Drinking Water Direct ive and this report contains a summary of

how the approach to regulat ing for safe , clean drinking water for al l has

developed over two decades. An overview of how this translates into

act ion in the region is contained in the Planned drinking water

improvements sect ion. Addit ional ly, Annex 4 contains information about

the schemes of work del i vered by companies in 2010 and those planned

for delivery over the next four years.

In reviewing drinking water qual ity in 2010, the Inspectorate considers that

two topics are worthy of highl ight ing to the industry. The f irst concerns the

number of events and failures of drinking water standards which have been

due to cross-connect ions or misconnect ions between the domestic water

supply and other sources, for example rainwater, pr ivate water suppl ies

and in one instance a sewer. These defects general ly occ ur at points close

to the consumer, therefore the r isk to publ ic health is high. Companies

need to give high pr iority in their water safety plans to control measures

to address these r isks, such as accurate records of network assets, the

competency of those who work on the network and more appropriate

targeting and priorit isat ion of f it t ings inspections. Although companies

have recently been identifying and taking enforcement act ion in relat ion

to cross-connect ions between the publ ic water supply and eith er domest ic

rainwater harvest ing systems or pr ivate water suppl ies, the Inspectorate

has found it necessary to remind a number of companies that f it t ings

inspect ions need to be carr ied out when investigating failures of drinking

water standards, part icular ly in relat ion to the following parameters: taste,

odour, lead, copper, nickel, E.col i and Enterococci. As a result of changes

to the regulat ions to bring them into l ine with the EU Drinking Water

Direct ive, it is mandatory to consider carrying out f it t ings inspections as

part of investigations into failures ar is ing in public buildings and also when

requested by a local author ity in relat ion to r isk assessments of private

water suppl ies. Companies need to make sure that these changes have

been ref lected in their policies and pract ices relat ing to f it t ings

inspect ions, which should be given a higher prof i le in relat ion to water

Thames reg ion

7

safety plan methodology and should be taken into account dur ing

regulatory r isk assessments.

The second observation concerns bulk suppl ies. These are situations

where one water company relies on another for a source of either raw or

treated water. In relat ion to a number of events or failures of drinking

water standards, it is evident that arrangements in relat ion to these bulk

suppl ies are less than adequate. In part icular, companies who import bulk

suppl ies are reminded that they are under a duty to carry out a full r isk

assessment and it would be advisable for there to be formal arrangements

to ensure that such suppl ies are both wholesome and f it for human

consumpt ion before supply to their own customers. The regulatory r isk

assessment (and formal agreement) must include arrangements for

alternate suppl ies of water in the event of either a quality or quantity

event. There is a need for joint ly agreed r isk assessments , ensuring full

awareness of the control measures with clear l ines of accountabi l i ty and

communication under both normal and abnormal operat ing situations.


8

Water supply arrangements

Five water companies supply dr inking wa ter in the Thames region: Sutton

and East Surrey Water (SES), Thames Water (TMS) and Veolia Water

Central (VCE). This includes two inset appoint ees; SSE Water (SSE)

suppl ies water in Hale Vi l lage in Tottenham, London, Kennet Island in

Reading, Bromley Common in south east London and Park Views in

Epsom; and Independent Water Networks Ltd (IWN) supplies water at The

Bridge, Dartford and at the Kings Cross Development in London.

Figure 1: Map il lustrating sources of drinking water by zone across

the region

Much of the water suppl ied in the region is surface water (65%) abstracted

f rom lowland r ivers such as the Thames, Kennet, Eden, Cherwell and

Til l ingbourne. Most r iver water is held in large, raw-water storage

reservoirs before being drawn of f for treatm ent. Together with other

reservoirs l ike Farmoor (Oxford) and Bough Beech (Edenbridge) these

strategic reserves are replenished over the winter and drawn down in

summer.

Thames reg ion

9

Groundwater provides a valuable water resource (34%) with most

boreholes drawing f rom the chalk, oolyt ic l imestone or greensand aquifers

in the region. A small proport ion (1%) of water suppl ies in the region can

be drawn from either groundwater or surface water sources.

Summary facts about the drinking water supply infrastructure of the

region are set out in Table 2 along with outl ine geographical and

demographic information.

Table 2: Key facts about the Thames region supply arrangements

Key facts

Population supplied Water supplied (l/day) Number of local authorities (with a further 21 partially covering the region)

12,323,000 3,825 million 63

Abstraction points Treatment works Service reservoirs Water supply zones Length of mains pipe (km)

404 203 546 333

49,393

Area of supply

Bedfordshire (part), Berkshire (part), Buckinghamshire (part), Essex (part), Gloucestershire (part), Hampshire (part), Hertfordshire, Kent (part), Inner London, Outer London (part), Oxfordshire, Surrey (part), West Sussex (part), Warwickshire (part), Wiltshire (part)

Water composition

Surface sources Groundwater sources Mixed sources

65% 34%

1%


10

Drinking water quality testing

Throughout 2010, water companies sampled drinking water across the

region to test for compliance with the standards in the drinking water

regulat ions. Almost half of the tests were carr ied out on dr inking water

drawn from consumers’ taps selected at random. For monitor ing purposes,

company water supply areas are divided into zones based on populat ion

(maximum 100,000). General ly , zones are sampled at consumers’ taps with

the number of required tests being greatest in zones with larger

populat ions. Other sample locations are water treatment works and treated

water (service) reservoirs. Col lect ively , the f ive water companies carr ied

out a total of 662,733 tests during 2010. Only 164 of these tests failed to

meet the standards set down in the regulat ions.

Table 3: Number of tests carried out by companies in the region

Company

Place of sampling

Number of

tests per

company

Estimate

of

populat ion

Water

treatment

works

Service

reservoirs

Consumers’

taps

(zones)

Independent Water Networks

0 (0)

0 (0)

210 (2)

210 1,000

SSE W ater 0

(0) 0

(0) 850 (4)

850 1,000

Sut ton and East Surrey Water

14,852 (8)

8,265 (32)

17,623 (20)

40,740 648,000

Thames Water

116,869 (102)

93,800 (376)

226,293 (237)

436,962 8,630,000

Veol ia Water Centra l

78,585 (83)

34,515 (134)

70,912 (70)

184,012 3,043,000

Region overall

210,306 (194)

136,580 (542)

315,888 (333)

662,774 12,323,000

Note: Numbers in b rackets re f lec t the number o f works , reservo i rs or zones oper ated by that company in the reg ion in 2010 . Some companies a re perm i t ted to ca r ry out some tes ts on samples taken f rom supply po in ts ra the r than f rom consumers ’ taps .

The regulat ions require companies to test for specif ied parameters at

prescribed f requencies. Most of the test ing is f or parameters with

European or national standards, however, water companies are also

required by the regulat ions to test for other parameters , such as

ammonium, sulphate and colony counts.

Thames reg ion

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A summary of the results of test ing by companies for each parameter can

be found on the DWI website (www.dwi.gov.uk) and on the CD

accompanying this report.

Drinking water quality results

The key water quality results for the Thames region are presented in two

tables, one showing the results for microbiological parameters (Table 4),

the other deal ing with chemical and physical parameters (Table 6).

The microbiological quality of water is discussed f irst. Companies report

al l the results of the tests on a monthly basis to the Inspectorate . Also,

tables in Annex 6 describe the performance of each company supplying in

the region.

Microbiological quality

To protect public health, microbiological standards have to be met at each

individual treatment works and service reservoir. The results co nf irm the

overall microbiological safety of drinking water suppl ies in the region.

The signif icance of the individual test results for each microbiological

parameter at each location varies and a single posit ive result cannot be

interpreted without other information. Al l companies are expected to follow

best pract ice as set out in The Microbiology of Dr inking Water publ ished by

the Standing Committee of Analysts (SCA) which can be found by vis it ing

the Environment Agency’s website ( www.environment-agency.gov.uk).


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Table 4: Microbiological tests

The number of tests performed and the number of tests not meeting

the standard

Parameter Current

standard

Total number of tests

Number of tests not meeting

the standard

Addit ional information

Water leaving water t reatment works

E.col i 0/100ml 33,659 2 TMS (2)

Col i form bacter ia 0/100ml 33,659 8 SES (1) , TMS (6) , VCE (1)

Clostr id ium per fr ingens

0/100ml 9,381 7 TMS (7)

Turbid i ty1 1NTU 33,647 3 TMS (2) , VCE (1)

Water leaving service reservoirs

E.col i 0/100ml 27,320 4 TMS (4)

Col i form bacter ia

0/100ml in 95% of tes ts

at each reservoir

27,320 18

TMS (17), VCE (1) Al l 542 reservoirs in the region met the 95% compl iance ru le

Water sampled at consumers’ taps

E.col i 0/100ml 31,683 4 SES (1) , TMS (3)

Enterococc i 0/100ml 2,505 1 TMS (1) 1Turb id i ty is a cr i t ica l contro l parameter for wate r t reatment and d is in fect ion.

E.coli at works and service reservoirs

In 2010, a total of 33,659 tests at works were carr ied out by al l t he

companies across the region and E.col i was detected in two samples

(TMS). At service reservoirs, a total of 27,320 tests were carr ied out and

E.col i was detected in four samples (TMS).

On detect ing E.col i, companies are required to act promptly to protect

public health. Their immediate response when f inding E.col i at a works

or service reservoir is to sample again, and more widely, to conf irm that

water being received by consumers is safe. In 2010, these addit ional

tests gave sat isfactory results in al l cases and there were no subsequen t

E.col i fai lures.

Fol lowing an E.col i fai lure and repeated detect ions of col iform bacteria in

March at North Orpington works (near Bromley , Kent), Thames Water took

the works out of supply. A few days before each microbiological fai lure the

plant failed the automatic membrane integrity check requir ing a vis it by a

technician to investigate and restart the works. Raw water at this s ite

intermittently contains E.coli and performance of one of the membrane

Thames reg ion

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stacks is only marginal ly acceptable. Records also show the occurrence of

short l ived turbidity spikes. All this information pointed towards suboptimal

operat ion of the site and membrane breakthrough as the probable cause of

the E.coli fai lure. The company reviewed the performance of each

membrane stack with module pinning or replacement carr ied out where

necessary before the site was returned to supply in December (for further

detai ls see Annex 3) .

In September, Thames Water took Dancers End works (near Aylesbury) out

of supply following an E.coli fai lure. Col iform bacteria were detected at the

same t ime. While the raw water quality was within the histor ic range ,

levels had increased just prior to the failure. The company investigation

identif ied some routes of ingress into the bui l ding which houses the wel l

head. The contr ibutory factors for this failure were probably a general lack

of site maintenance combined with raw water quality deter iorat ion.

This site remains out of service (see Annex 3 for further detai ls) .

E.col i was detected on four separate occasions f rom the following service

reservoirs operated by Thames Water : Goose Green Tower (July), Hornsey

Lane (August), Farnborough Tower (September) and Cockfosters

(October). This compares unfavourably with the single failure at a service

reservoir in the region in 2009.

E.col i and col iform bacteria were detected in a routine sample col lected

f rom Goose Green Tower , Hoddesdon, Hertfordshire, in July 2010.

Fol lowing this failure , further invest igative samples were taken by the

company from the tower and sur rounding supply area. A further sample

taken at the tower was unsat isfactory so Thames Water isolated the tower

and drained, inspected and cleaned it before returning it to service in July.

No ingress into the tower was found , but the roof of the tower discharges

onto the sampling faci l i ty bui lding dur ing heavy rain which the company

concluded to be the cause of the exceedences. Al l remedial works at

Goose Green Tower, including relocat ion of the sampling facil i t ies, were

completed by the end of September. Fol lowing complet ion of these works,

a programme of enhanced monitor ing was implemented at the site for a

period of four weeks. All samples col lected dur ing this period, and al l

subsequent samples from this site, were clear of bacterial contaminat ion.

At Hornsey Lane reservoir , in North London, in response to the E.coli

failure in August, Thames Water carr ied out enhanced monitor ing at

upstream reservoirs and works, and downstream in Crouch End and

Gospel Oak zone, and al l the results were satisfactory. The company

took the reservoir out of supply for an internal inspect ion and did not f ind

points of ingress, but found that the sampling facil i t ies were defect ive.

The reservoir was returned to service in October.


14

In September, E.col i and coliforms were detected in a sample col lected

f rom Farnborough Tower reservoir . Fol low-up samples f rom the tower

contained coliform bacteria, E.coli and Enterococci and a consumer ’s tap

sample f rom an adjacent property contained col iforms and Enterococci.

When Thames Water inspected the tower, structural def iciencies in the

roof wall jo int of the tank were found. The company also discovered a

hornets ’ nest which had fallen into the reservoir. Remedial and cleaning

works were carr ied out before the tower was returned to servi ce in

October.

Fol lowing an E.col i fai lure and mult iple detect ions of col iform bacteria at

Cockfosters reservoir , (North London), in October, Thames Water

inspected their reservoir. While it was generally in good condit ion, a small

leak was identif ied on the instrumentat ion/dipping chamber where there

were unsealed joints. Fol lowing repairs the reservoir was cleaned,

dis infected and returned to supply in January 2011 (see Annex 3).

Table 5: Detection of E.coli and Enterococci at treatment works,

service reservoirs and consumers’ taps

Company

E.coli in water

leaving treatment

works

E.coli in water

leaving service

reservoirs

E.coli at consumers’

taps

Enterococci at

consumers’ taps


0 – 0 0 – 0 0 – 7 0 – 3

SSE W ater 0 – 0 0 – 0 0 – 38 0 – 14

Sut ton and East Surrey Water

0 – 2 ,122 0 – 1 ,653 1 – 1 ,669 0 – 160

Thames Water 2 – 18,728 4 – 18,764 3 – 22,177 1 – 1 ,803

Veol ia W ater Centra l

0 – 12,809 0 – 6 ,903 0 – 7 ,792 0 – 525

Region overall

2 – 33,659 4 – 27,320 4 – 31,683 1 – 2 ,505

Note: Resu l ts are shown a s the number o f pos i t i ve tes ts – the to ta l number o f tes ts .

Coliform bacteria at works

Testing for coliform bacteria gives reassurance that water entering the

supply was treated adequately to remove bacterial and viral pathogens .

Repeated occurrences of coliform bacteria in samples f rom the same

works in one year are thus of concern and require act ion to be taken.

In 2010, this situation occurred twice at one site: North Orpington (see the

E.col i at works sect ion).

Thames reg ion

15

Following the detect ion of coliform bacter ia in May a t Cheam works near

Sutton in Surrey, Sutton and East Surrey Water sampled comprehensively

f rom the upstream works and throughout the distr ibut ion system , and al l

results were sat isfactory including an alternate sampl e point at the works.

However, col iform bacteria were detected persistent ly f rom the original tap

at the works. The company installed new sampling l ines and all further

samples have given satisfactory results.

Coliform bacteria were detected at Hornsey works (North London) in a

sample taken on the same day in October as the works was returned to

service af ter a period of shutdown for changes to be made to the site

control system. Thames Water took the site out of service and af ter

checking that al l contemporaneous downstream samples were satisfactory,

concluded that the sample l ine had become contaminated. The sample

facil i t ies were cleansed and the site returned to supply in ear ly November

with an enhanced monitor ing regime. However, two of ten subsequent

samples contained col iform bacteria so the works was taken out of supply

again. Since then the company has in it iated a series of remedial act ions

including: desludging of the outlet channels f rom the d issolved air

f loatat ion plant, changing the operat ing regime so that more f i l ters are in

service, increasing the number of in -service rapid gravity f i l ters so that

each is operating at a lower f low rate, dis infect ing al l sample l ines and

checking the performance of turbidity monitors and, where appropriate,

instal l ing new ones. The company returned the works to service in

November.

At Ashford Common works there was a col iform failure in September.

Thames Water’s follow up samples at the same tap were sat isfactory . The

Inspectorate has noted a similar occurrence at Ashford in 2008. On that

occasion the company identif ied the organism as Sphingomonas (non-

col iform) and l inked the posit ive detect ions to the return to service of three

slow sand f i l ters, one each day, af ter maintenance (see comments about

Hampton slow sand f i l ter works in the Clostr idium perfr ingens section).

At Cleeve Works, near Goring in Berkshire, col iform bacteria were

detected in August. The company carr ied out a thorough sampling survey

at the t ime and found nothing untoward. Any unexplained failure at a works

should prompt a review by the company of the regulatory r isk assessment

and the associated raw water monitor ing programme to proactively

determine if an intermittent problem exists.

The Inspectorate has noted that col iform bacteria were found in eight

samples f rom treatment works in the Thames region ( 1 SES, 6 TMS,

1 VCE) during the year and this information wil l be taken into account

during the Inspectorate’s r isk -based programme of technical audit .


16

Clostridium perfringens

This organism is a spore-forming bacterium that is exceptional ly resistant

to unfavourable condit ions in the water environment , such as extremes of

temperature and pH, and disinfect ion processes such as chlor inat ion and

ultraviolet l ight. I t is a normal component of the intest inal f lora of up to

35% of humans and other warm-blooded animals. These characterist ics

make it a useful indicator of either intermittent or historical f aecal

contamination of a groundwater source or surface water f i l t rat ion plant

performance. The detect ion of any Clostr idium perfr ingens should tr igger

an invest igation by the water company.

In 2010, out of 9,381 samples across the region, seven did not meet the

specif ied value (7 TMS). Four of these fai lures at consumer tap samples

may have been l inked to a deteriorat ion in the performance of slow sand

f i l ters at Hampton works, in south west London . The remainder were

isolated occurrences in dif ferent surface water der ived zones. In l ine with

guidance issued previously, the Inspectorate expects the companies to

review and update their regulatory r isk assessments to take account of

detect ions of Clostr idium perfr ingens in consumer tap samples. In Drinking

water 2009 i t was explained that posit ive detect ions in surface water

derived supplies are usual l y indicat ive of accumulat ions of mains deposits

and point towards the need for information on failures to be taken into

account in companies’ Distr ibut ion, Operation and Maintenance Strategies

(DOMS) to pr ior it ise f lushing work.

On four occasions in February, March and Apri l the detect ions of

Clostr idium perfr ingens at consumers’ taps were al l in zones fed with water

treated at Hampton works. During January into February, f i l tered water

quality at the works deteriorated as evidenced by breaches of operational

cr iter ia and some samples of treated water entering supply in February

and March contained Clostr idium perfr ingens . The Inspectorate was cr it ical

of Thames Water for not making the l ink between the situat ion at Hampton

works and the failures at consumers’ taps. When , in May, the Inspectorate

asked questions of the company, it was explained that the severe cold

weather event had resulted in low water temperatures and a high works

output which had exacerbated exist ing problems with some f i l ter beds. I t is

well known the performance of slow sand f i l ters decl ines in winter, due to

the impact of cold water on the biological processes within these f i l ters;

accordingly, the Inspectorate is disappointed to note that the company had

not prepared adequately for a predictable situat ion. The company has

since embarked on a review of slow sand f i l ter beds at all i ts relevant

treatment works result ing in an enhanced programme of f i l ter

refurbishment pr iorit ised on individual f i l ter bed performance. Delivery of

this plan is subject to senior management review on a monthly basis . The

Inspectorate is c losely scrut inis ing information provided by the company

Thames reg ion

17

for evidence of improved operat ional management in relat ion to all i ts

treatment works (see the Coliform bacteria and E.col i at works sections).

Turbidity at works

Turbidity is a measure of how much l ight can pass through water and

indicates the condit ion or ‘cloudiness ’ of water. Turbidity is caused by

part ic les suspended in the water and is an important cr it ical control

measure of the performance of disinfect ion. Turbidity is measured at two

points in the water supply chain, at treatment works where a value of

1NTU appl ies and at consumers ’ taps where the standard of 4NTU appl ies.

The following discussion focuses on the results of samples taken at

treatment works.

During 2010, there were three occasions when a turbidity value of more

than 1NTU was reported at a works in the region (2 TMS, 1 VCE). This is

an improvement compared to last year when there were 12 turbidity

failures (9 TMS and 3 VCE).

A turbidity fai lure in September , at Horton Kirby works (near Dartford) , was

found to have occurred because the site had only started pumping 15

minutes pr ior to sample col lect ion. Thames Water attr ibuted the failure to

suspended chalk part icles. The Inspectorate noted that a similar s ituat ion

occurred in 2009 and in March 2011 Thames replaced the non-return

valves on the boreholes to prevent any potential backf low and associated

mobil isat ion of chalk deposits. The company also re minded samplers about

adequately f lushing taps to obtain a representat ive sample and reviewed

the site start up condit ions.

At W ickerhall works near Royston , operated by Veolia Water Central , a

turbidity failure occurred in September. This works comprises a reservoir

which acts as a nitrate blending site drawing water f rom four other

treatment works: Eagle Tavern, London Road, Sl ip End and Therf ield

Heath. The company ident if ied that the failure arose because of a c hange

in operation af fect ing f lows and al lowing water to stagnate within the out let

pipe. Changes were made to prevent a recurrence and there have been no

further failures since.

In response to a turbidity failure at Chingford South works in August ,

Thames Water checked the records f rom on-l ine monitors. These were

functioning correct ly and the readings were al l sat isfactory. The company

fast tracked analysis of the Cryptosporidium sample and no oocysts were

detected. There have been no previous or subsequent turbidity failures at

this s ite.


18

Coliform bacteria at service reservoirs

Testing for coliform bacteria gives reassurance that the qual i ty of water

held at these strategic points in the distr ibut ion system is adequately

maintained. The national standard requires that at least 95% of no less

than 50 samples collected f rom each service reservoir throughout one year

are f ree f rom all coliform bacteria. In 2010, al l 542 service reservoirs

( including water towers) in the region met the 95% compliance rule;

however, coliform bacteria were reported on 18 occasions (17 TMS and

1 VCE) and in four cases E.col i was also present (see the E.col i at works

and service reservoirs section). This compares favourably to the

22 failures recorded in 2009.

Two separate samples f rom Hil l Barn reservoir , near Wantage, contained

col iform bacteria in September which led Thames Water to take the

reservoir out of supply for an internal inspection. Ingress was discovered

around the roof joints and the company instal led a new bonded ro of

membrane. Af ter f lood test ing the reservoir was returned to supply.

The Inspectorate notes that this reservoir had not been inspected for 15

years. Companies are reminded that reservoir maintenance should be

proactive and preventat ive rather than failure driven.

A sample col lected by Thames Water f rom Common Hil l service reservoir ,

near Cr icklade, north of Swindon, in February contained col iform bacteria.

Further samples were satisfactory , but the company reported that the

cause was non-compliant sampling facil i t ies. There was a single sample

tap at this s ite with a manual valve enabling water to be drawn from one or

other of the compartments. The company has since upgraded the sampling

facil i t ies and the new sample tap draws water f rom the combined out let of

the two cel ls. The Inspectorate is disappointed to note this evidence of

non-compliant sampling facil i t ies 20 years af ter introduction of the

regulat ions. Given that the company ident if ied the def icient sampling

facil i t ies in its regulatory r isk assessment in 2008 , it is unsatisfactory that

the necessary improvements were not pr iorit ised by the company unt i l the

failure occurred in 2010.

At Flaxlands reservoir , near Wootten Bassett, when investigat ing a

col iform failure in July, Thames Water observed that the sample pumps

were not re-circulat ing correct ly. All subsequent samples have given

satisfactory results and h istorical raw water quality data f rom the upstream

works (Ashton Keynes) shows that the source has been free of coliform

bacteria and E.col i throughout the year.

In August, the invest igation by Thames Water of a detect ion of col iform

bacteria at Castlewood reservoir near Shooters Hi l l, south east London,

was l inked to air locks in the sample l ine on start up.

Thames reg ion

19

The Inspectorate has noted that col iform bacteria were found in

18 samples f rom service reservoirs in the Thames region dur ing the year

and this information wi l l be taken into account dur ing the Inspectorate’s

r isk-based programme of technical audit . The Inspectorate has noted that

much of the evidence from invest igatio ns this year points towards a wider

issue in relat ion to the insuf f iciency of water quality asset maintenance by

Thames Water.

E.coli and Enterococci at consumers’ taps

A total of 31,683 consumers’ taps were tested in 2010 for E.coli and four

were posit ive (1 SES, 3 TMS). Like E.col i , the presence of Enterococci is

indicative of faecal contamination and neither bacter ium should be found

in any sample. Out of 2,505 tests for Enterococci at consumers’ taps there

was a single fai lure (1 TMS) during the year. There was no indicat ion, f rom

information gathered by the water companies, of a faecal contaminat ion

event af fect ing other propert ies in these zones .

A sample col lected by Sutton and East Surrey Water at a consumer’s tap

in Carshalton, in October, contained E.coli together with col iform bacteria.

Although samples f rom neighbouring propert ies were satisfactory the

contamination persisted at the original tap and the company advised the

occupants to boi l their drinking water whi l e a f it t ings inspection was

arranged. The customer replaced the kitchen tap and f lexible hoses

attached to the incoming supply pipe which rect if ied the problem (see

Annex 3).

Both E.col i and coliforms were reported in samples col lected f rom

consumers’ taps by Thames Water f rom three d if ferent zones: Reading

West, South and Central (January), Mile End (Apri l) and Epping Forest

(September). In two of the three cases the company found evidence to

demonstrate tap hygiene was the cause and wr it ten advice was given to

the consumers.

Thames Water recorded Enterococci in a sample col lected in December

f rom a consumer ’s tap in the Edmonton supply zone in North London.

The company was refused access to col lect further samples af ter giving

the consumer precautionary boil water and tap hygiene ad vice. The

consumer reported that they rout inely boiled al l tap water . Samples f rom

neighbouring propert ies gave sat isfactory results (see Annex 3).

Chemical quality

The drinking water regulat ions set out the minimum test ing requirements

for all chemical and physical parameters. A full summary of the results of


20

test ing by each company, including the results for indicator parameters ,

is provided on the DWI website (www.dwi.gov.uk) and on the CD

accompanying this report.

The following text and Table 6 set out the results for those parameters

where there has been a failure to meet a European or national standard

(mandatory qual ity standards) and any other parameter of interest . In

addit ion, at the request of local author it ies, the results of test ing for

f luoride, iron, lead, manganese, nitrate, nitr ite and pesticides are given.

Table 6: Chemical and physical parameters

The number of tests performed and the number of tests not meeting

the standard

Parameter

Current standard or

specified concentration

1

Total number of tests

Number of tests not meeting

the standard

Additional information

Aesthetic parameters

– odour No abnormal

change

6,485 2 TMS (2)

– taste 6,471 6 TMS (6)

Aluminium 200μg/l 9,219 3 TMS (3)

Benzo(a)pyrene 0.01μg/l 2,499 1 VCE (1)

Copper 2mg/l 2,497 1 TMS (1)

Fluoride 1.5mg/l 2,397 0

Iron 200μg/l 10,155 21 SES (2), TMS (17), VCE (2)

Lead (current standard) 25μg/l 2,498 5 TMS (5)

Lead (future standard) 10μg/l 2,498 37 SES (2), TMS (31), VCE (4)

Manganese 50μg/l 9,070 3 TMS (1), VCE (2)

Nickel 20μg/l 2,498 4 TMS (3), VCE (1)

Nitrate 50mg/l 7,804 0

Nitrite 0.5mg/l 7,811 1 TMS (1)

Pesticides – total 0.5μg/l 1,445 0

Pesticide – individual2 0.1μg/l 41,191 3

Metaldehyde TMS (2), VCE (1)

pH (Hydrogen ion) 6.5 – 9.5 11,442 2 VCE (2)

Turbidity (at consumers’ taps)

4NTU 11,445 3 TMS (3)

Notes: 1For comparison, 1mg/l is one part in a million, 1μg/l is one part in a thousand million.

2A further 359 tests were done for aldrin, dieldrin, heptachlor, heptachlor epoxide, all of which met the

relevant standard.

Thames reg ion

21

Aesthetic parameters

Consumers expect their dr inking water to be clear and bright in

appearance and free from discernible taste or odour. In recognit ion of this

the regulat ions st ipulate national standards for colour, odour an d taste.

Companies are required to investigate the cause of any adverse result .

In 2010, a total of eight out of a total of 12,956 tests f rom consumers’ taps

in the region exhibited a posit ive taste or odour. All tests in the region met

the standard for colour.

The posit ive detect ions of taste and odour are summarised below in

relat ion to their nature and cause as determined by the invest igations

carr ied out by the companies. From this information it can be seen that

many were conf ined to a single property and did not ref lect a wider

problem in the water supply zone.

Softened: (8 TMS): this descr iptor relate s to samples where the tap

water has been art if icial ly sof tened; Var iously descr ibed by the test

panel as sweet, sal ine, earthy and bit ter , the investigations by

Thames Water conf irmed the presence of a water sof tener in the

eight propert ies ( in two cases there was both a posit ive odour and a

posit ive taste). The householders were advised that a mains fed tap

should be avai lable for drinking and cooking pu rposes. In one

instance, in the Twyford, Wargrave and Sonning zone , a three way

tap was instal led in the property but the sampler had made an error

when col lect ing the original sample.

Aluminium

Aluminium can occur natural ly in some drinking water sources.

Also, aluminium-based water treatment chemicals may be used at surface

water works to aid the process of f i l t rat ion.

In 2010, a total of 9,219 samples were tested for aluminium in the Thames

region. Sutton and East Surrey Water and Veol ia Water Centr al achieved

100% compliance with the aluminium standard. Just three tests exceeded

the standard (3 TMS) and none of these were related to process control

because aluminium is not used in the local treatment works.

A failure of the aluminium standard in the Clapton zone, in September,

was associated with a failure of the iron standard. Thames Water’s

investigation found that the sample bott le contained a large part ic le of

unknown or igin. In May, fol lowing a failure of the aluminium standard in

a sample f rom a property in South Hampstead, Thames Water tested more

widely and found another elevated aluminium result in a sample f rom a f lat

in a neighbouring block. Further samples gave sat isfactory results ,


22

however, the failures in the or iginal samples were con f irmed by repeat

analysis of the stored samples. Follow-up samples were satisfactory in

relat ion to another fai lure in August f rom a consumer’s tap sample in the

Syon Park zone.

The Inspectorate has noted that the company did not carry out f it t ings

inspect ions as part of the investigation of these failures in zones where

there is no evidence that would indicate they may have been caused by

local ised disturbance of historic mains deposits. Companies are reminded

that f it t ings inspect ions are an essent ial pa rt of the evidence required to

determine whether a failure is due to the domestic distr ibut ion system and,

following amendment of the regulat ions in 2010 is mandatory in relat ion to

public buildings.

Bromate

Bromate can be formed in drinking water if the surface water source

contains bromide and ozone is used in the treatment process. The process

of chlorination may also produce bromate, for example, through the use of

a sodium hypochlor ite solut ion containing bromide or when chlorine is

generated on site by electrolysis. In recent years, companies have put in

place control measures aimed at meeting the standard of 10μg/l. In the

Thames region, out of a total of 1,474 tests, there were no failures of the

bromate standard in 2010.

In previous years, the Inspectorate has reported on the act ions that were

being taken by the Environment Agency and two water companies to

address the r isk to drinking water f rom bromate pollut ion of a strategic

chalk aquifer f rom an industr ial s ite at Sandr idge, Hertfordshire.

The groundwater is a major source of water supplies for two companies in

the region (Thames Water and Veolia Water Central). By March , Veolia

Water Central had completed the f inal steps in its legal ly binding

programme of work which involved implementing a series of control

measures whereby output f rom its Essendon works is reduced alongside

increased abstract ion f rom boreholes at East Hyde and Wheathamstead

(for further detai ls see Drinking water 2009 ).

Copper

Copper in drinking water usual ly der ives f rom copper pipes and f it t ings in

household plumbing. In general, water suppl ies in the UK are not

aggressive towards copper, but there can be occasional problems with new

plumbing installat ions. In 2010, a total of 2,497 tests were carr ied out for

copper across the region and al l but one met the standard (2mg/l).

Thames reg ion

23

A level of 2.02mg/l copper, together with lead at a level of 29.9 μg/l , was

reported in a sample from a consumer’s tap in the Plumstead zone in June.

Thames Water carr ied out a f it t ings inspection an d advised the

householder about a number of irregulari t ies, part icular ly the inadvisabi l i ty

of mixing dif ferent types of plumbing metals and the correct sequence

required. The company made a second inspection vis it which conf irmed

that the defects had been rect if ied and samples taken af ter the remedial

work were sat isfactory for both copper and lead.

Fluoride

Traces of f luoride occur naturally in many water sources, part icularly in

groundwaters. For example, f luoride is found in water abstracted by Veolia

Water Central f rom the Reading Beds in West Essex and in an area south

of Reading (around Burghf ield and Tadley) supplied by Thames Water.

Consumers can obtain specif ic information on the level of f luoride in the

drinking water supply to their home or work place f rom their water

company.

Fluoride is not removed by conventional water treatment. Some companies

f luoridate water suppl ies where required by the local health author ity as a

protect ion against tooth decay. There are no operat ional f luoridation

schemes in the Thames region, and in 2010, all 2,397 tests for f luoride

taken across the region met the regulatory standard (1.5mg/l). Current ly,

there is legislat ion in Parl iament proposing organisational change in the

health service and this wi l l alter responsibi l i t ies for the commissioning and

funding of f luoridat ion schemes. Please refer to the DWI website

(www.dwi.gov.uk) for more information on f luoridat ion.

Lead

The pipe connecting a property to the water company m ain, together with

internal plumbing, is the most common source of lead in dr inking water.

Propert ies bui lt or renovated since 1970 are unlikely to have lead pipes

and lead solder was banned for use with copper dr inking water

instal lat ions in the early 1970’s. The only other recognised source of lead

in dr inking water in some bui ldings is f it t ings made from brass. The extent

of lead pick up depends on various factors; temperature, acidity (pH),

water hardness, the length of pipe and the t ime that water is l ef t to stand

in the pipe (stagnation) before it is drawn off .

The monitoring data col lected by companies during 2010 has been added

by the Inspectorate to that gathered in previous years to provide an

updated picture of progress in the region and for the industry, towards

http://www.dwi.gov.uk/


24

meeting the future standard for lead of 10µg/l by the end of 2013 (see

Figure 7).

Figure 7: Percentage of tests meeting the current and future standard

for lead between 2001 and 2010

95

96

97

98

99

100

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Perc

en

tag

e m

eeting

sta

ndar

d

25µg/l Regional 10µg/l Regional

25µg/l Industry 10µg/l Industry

Figure 7 summarises a decade of randomised consumer tap sampling for

lead by the industry. The data conf irm the benef ic ial ef fect of water

treatment which has been introduced over the same period. In part icular,

in the Thames region, the percentage of annual tap samples fai l ing the

future lead standard of 10µg/l has fallen f rom above 4% in 2002 to about

1.5% in 2010.

Figure 8 shows where failures of the future standard for lead of 10µg/l

occurred in 2010 compared to 2004. Water companies notify both the

consumer and the relevant local authority whenever a f ailure of the future

lead standard occurs. In 2010, the Inspectorate was notif ied of a total of

f ive failures of the current standard of 25µg/l (5 TMS) and 37 failures of

the future standard (2 SES, 31 TMS and 4 VCE) in the region. Four out of

the f ive fai lures of the current standard in 2010 were in Thames Water’s

North London area of supply (South Enf ield, Oakwood, Plumstead,

Finsbury Park zones) and the f if th was in South West London (New Maldon

zone).

Thames reg ion

25

Figure 8: Failures of the future standard for lead in 2004 compared to

2010

In the Thames region, to date, just one company (Thames Water) has put

in place act ion plans under Regulat ion 28 to address the r isk of not

meeting the future lead standard by the end of 2013 in Oxford and the

North London area. Fol lowing the successful introduction of water

treatment, the work of companies needs to increasingly f ocus on rais ing

awareness among vulnerable groups of people in communit ies where the

r isk from lead is highest. The Inspectorate expects companies in the

Thames region to be more proactive in developing these act ion plans

emulat ing best pract ice f rom across the industry , such as Anglian Water’s

in it iat ive which targets at r isk groups identif ied by health protect ion teams

and Pr imary Care Trusts , and of fers a f ree lead test with f ree replacement

of communication pipes if the sample exceeds the 2013 standard of 10µg/l.

Anglian Water’s dedicated Lead Strategy Team are also identi fying

opportunit ies to work in tandem with local authorit ies and housing

associat ions – combining their schemes to refurbish council or housing

associat ion owned propert ies with the company’s lead communication pipe

replacement work; therefore result ing in the el iminat ion of lead pipework to

these propert ies.


26

In addit ion, dur ing 2010, companies in the region have responded to 349

consumer requests to check the level of lead in drinking water in a

part icular property.

Nickel

Nickel may be present in coatings on modern tap f it t ings. In 2010, a total

of 2,498 tests were carr ied out for nickel and all but four (3 TMS, 1 VCE)

met the standard (20μg/l).

A level of 159μg/l nickel was reported in a sample collected in May, by

Veol ia Water Central , f rom a consumer ’s tap in the Codicote zone near

Welwyn, which at the t ime was fed by a bu lk import of water f rom Anglian

Water ’s Grafham works. The invest igation identif ied the kitchen tap in the

property as the most l ikely cause and the consumer was given wr it ten

advice.

Thames Water recorded values between 22.8 to 52.1μg/l in samples

col lected f rom consumers’ taps in the Kensington and Mile End zones,

both in March, and the Thame zone in November. In each case the

company wrote to the consumer identifying the tap f it t ing as the probable

cause.

The Inspectorate expects companies to take nickel and other relevant

failures into account during their f i t t ings inspect ion programme in the

region, thereby gathering information on the types of water f it t ings that are

giving r ise to water quality problems.

Nitrate and nitrite

Nitrate occurs natural ly in all source waters due to the decay of vegetable

material in soil. Nitrogenous fert i l isers used on arable farmland are a

signif icant source of nitrate in groundwater. Rainfall washes nitrate f rom

the soi l into lakes, r ivers and streams. Nitrate levels can be reduced by

water treatment or by blending with another, low nitrate, water source.

In 2010, al l tests for nitrate met the standard (50mg/l).

From extensive information gathered by the water companies in the

Thames region, a l ikel ihood of drinking wa ter suppl ies in the region fail ing

the nitrate standard in the longer term has been conf irmed at some sites.

As a consequence, legally binding agreements are in place for addit ional

treatment by Thames Water at Wantage and Westerham works due for

complet ion by September 2012 and similarly at Veolia Water Central ’s

Kings Walden works by March 2014.

Thames reg ion

27

Nitr ite may be formed when chloramine is used as the residual dis infectant

to maintain the microbiological qual ity in the distr ibut ion network.

The formation of nitr ite is controlled by careful optimisat ion of the

chloramination process. Chloramine is widely used as the residual

dis infectant across the region’s urban areas: for example , throughout the

area suppl ied by Sutton and East Surrey Water and by Thames Water in

central London. Addit ional ly, chlor ine residual in the form of chloramine is

used in Veolia Water Central’s Luton supply area (der ived f rom Anglian

Water’s Grafham works). Nitr ite can also form in samples of water, af ter

col lect ion and before analysis, especial ly if the sample is not kept cool.

In 2010, al l but one (TMS) of the 7,811 tests carr ied out across the region

for nitr ite met the standard (0.5mg/l) .

In September, Thames Water detected nitr ite in a sample collected f rom a

customer ’s tap in the Long Marston zone in September. This zone is on the

border between two water companies. Further samples also showed

elevated levels of nitr ite and the company l iaised with Angl ian Water about

the operat ional performance of an upstream booster stat ion. Init ia l ly,

Angl ian Water did not ident ify any operat ional def iciencies with their

booster stat ion, but subsequently this was shut down for more detai led

investigations. Thames Water carr ied out f lushing and implemented

enhanced operat ional monitoring in the Long Marston zone. This small

zone has now been incorporated by Thames Water into the adjacent

Finmere zone which is also suppl ied by an import f rom Anglian Water’s

Grafham works.

Pesticides and related products

This group of substances, generically cal led pesticides, includes many

organic chemicals ranging from weed kil lers, to insectic ides and

fungicides. Water sources may contain traces of pestic ide residues as a

result of agricultural use (pest control on crops) and non -agricultural uses

(herbicides for weed control on highways etc.). Water companies are

required to assess the r isk to drinking water suppl ies of pestic ide use in

their catchments and test for those which might be present. Companies

have documented potential and actual pestic ide hazards through their

Regulat ion 27 r isk assessments , which are informed by raw water

monitor ing and identify the control measures in place. When pestic ides are

f irst detected, water companies wi l l enhance their monitoring of raw water

and not ify the Environment Agency to faci l i tate appropriate act ion to

safeguard drinking water quality.

In 2010, none of the tests in the region exceeded the standard for total

pestic ides. Likewise, there was 100% compliance (359 tests) for the four

pestic ides with a standard of 0.03μg/l. Out of a total of 41,191 tests for


28

those individual pest ic ides with a standard of 0.1μg/l , just three exceeded

the standard. The circumstances and substances involved are summarised

below.

Metaldehyde

Metaldehyde is the act ive ingredient in some slug pel lets. The standard is

0.1µg/l.

In 2010, metaldehyde was detected between January and March on three

occasions at levels just above the standard (maximum 0.11µg/l).

The zones af fected were Knebworth and Tewin zone (Veol ia Water

Central) and two zones operated by Thames Water (Finmere, Godington

and Newton zone and Long Marston zone). The companies have legally

binding agreements in place to carry out catchment control measures

(Annex 4). This is a signif icant improvement on the previous year , when

metaldehyde was detected in 42 samples col lected by three companies

across the region (8 SES, 27 TMS and 7 VCE).

The legal ly binding agreements , which last unti l 2015, set out the work

companies in the Thames region are now carrying out with a var iety of

stakeholders on the management of pesticides. Catchment management

off icers have been recruited who regular ly meet with farmers,

manufacturers, agronomists, Natural England and the Environment

Agency. Since 2009, there has been a general decl ine in the level s of

metaldehyde ident if ied through raw water monitoring and a growing

knowledge of the prevalence and seasonal ity of use of this substance

enabl ing focused act ion to be taken.

pH (Hydrogen ion)

pH is a measure of the acidity of the water. Where water i s supplied f rom

upland areas the water naturally picks up iron and humic acids f rom the

peaty soi ls, result ing in sl ight ly acidic water with a low pH, which is

commonly descr ibed as ‘sof t water’. Such water has an increased potent ial

to corrode iron pipes and leach mater ial f rom cement l ined mains. Acidity

can also be affected when water is art if ic ial ly sof tened by a treatment

device in a consumer‘s property. The standard is a range of 6.5 – 9.5.

In the Thames region, out of a total of 11,442 tests, the standard was

exceeded on two occasions in 2010 (2 VCE).

Veol ia Water Central recorded two failures of the pH standard in samples

col lected f rom consumers’ taps and the cause in each case was a point of

use treatment device instal led within the property. The values recorded

were 6.0 and 6.4, both below the standard of 6.5. The investigation of the

Thames reg ion

29

failure in the Hitchin zone, in June, found that the original sample had

been taken from a f i l tered water tap. The householder was reassured that,

although fail ing to meet the pH standard, the result was consistent with the

instal led treatment device and the water was safe to drink.

The invest igation by Veol ia Water Central of a pH failure, 6.0pH value, in

the Hemel Hempstead zone in September , ident if ied that there was no tap

fed direct ly f rom the mains supply. There were two taps, one fed by a

reverse osmosis treatment unit intended as the drinking water supply and

the other was a sof tened supply for other domestic purposes. The pH

failure was associated with the reverse osmosis unit . Coliform bacteria and

a low pH were recorded in a follow-up reverse osmosis tap sample,

whereas the sof tened supply proved satisfactory for both parameters.

Advice was given to the customer.

Consumers seeking the benef its of sof tened water for washing and other

domestic purposes should be advised to retain a tap connected direct ly to

the mains for drinking and cooking .

Maintaining water quality in distribution

The parameters most commonly l inked to aesthet ic water qual ity problems

are iron and manganese. These substances may be present natural ly in

raw water sources. I ron compounds may be added as part of water

treatment or can be released as a consequence of the corrosion of iron

mains. The most severe problems tend to be where the d istr ibut ion

network contains a large proport ion of old cast iron mains. Effect ive water

treatment reduces iron and manganese at source, but if treatment has

been inadequate historical ly then iron and manganese wil l have

accumulated in local parts of the distr ibut ion system. When these deposits

are disturbed, they may cause black , brown or orange discolourat ion of the

water, which in turn results in breaches of the turbidity standard. In 2009,

across the Thames region there were 17 failures of the iron stand ard

(3 SES, 11 TMS, 3 VCE), whereas in 2010 this had r isen to 21 iron fai lures

(2 SES, 17 TMS, 2 VCE). This deteriorat ion was observed in the area

suppl ied by Thames Water. Also, there were more manganese failures in

2010: 3 (1 TMS, 2 VCE) compared to no failures in 2009. A related, but

less f requent , problem that may arise in the distr ibut ion network is the

deteriorat ion of old coal tar l inings of cast iron mains causing failures of

the standards for polycycl ic aromatic hydrocarbons including

benzo(a)pyrene. In 2010, there was 1 sample (VCE) which fai led the

standard of 0.01μg/l compared to two in 2009 (1 TMS, 1 VCE).

Elevated levels of iron or manganese are object ionable to consumers

because the water may appear turbid, it may have an astr ingent or bit te r


30

taste and the deposits are unsightly and may stain water f it t ings. Since

1996, the Inspectorate has been measur ing the progress of companies ’

distr ibut ion maintenance work to address these problems with an index

made up of the three parameters ( iron, manganese and turbidity). Figure 9

i l lustrates the improvement across the region generally and also shows the

recent decl ine in the index for Thames Water.

Figure 9: Percentage of the tests meeting the standards for turbidity,

iron and manganese.

99.20

99.30

99.40

99.50

99.60

99.70

99.80

99.90

100.00

1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

Perc

enta

ge m

eeti

ng s

tand

ard

Sutton and East Surrey Water Thames Water

Veolia Water Central SSE Water

Note: IW NL began supp ly ing wate r in t he Thames reg ion in 2010. A l l o f the i r tes t s met the

s tandards for t u rb id i t y , i r on and manganese.

Discolourat ion of water supplies of ten prompts consumers to contact their

water company. The rate of contacts in 2007 and 2010 for each supply

zone is mapped in Figures 10 and 11.

Thames reg ion

31

Figure 10: Rate of consumer contact per 1,000 population reporting

black, brown or orange water in 2007

Figure 11: Rate of consumer contact per 1,000 population reporting

black, brown or orange water in 2010


32

The two maps i l lustrate the improving situation over the four-year per iod

(2007 to 2010) in relat ion to discolourat ion contact s f rom consumers;

part icularly between Swindon and Newbury, to the north and east of

Haslemere and around Oxford. Although showing some improvement ,

contacts persist in the area to the south of Harlow.

Iron

A failure of the iron standard in Apri l , in the Salfords zone, was

investigated by Sutton and East Surrey water. The company conf irmed a

wider problem when a further sample taken af ter localised f lushing also

failed the standard. A programme of regular f lushing has been put in place

since. The Inspectorate expects the f indings of invest igations into failures

to inform companies’ Distr ibut ion, Operat ion and Maintenance Strategies

(DOMS).

In 2010, Thames Water recorded a series of iron failures in zones in its

North Oxfordshire supply area. In Charlbury Overnorton and Woodstock

zone there were two failures of the iron standard in January (30 7.6μg/l)

and June (773.4μg/l); a value of 283.8μg/l was recorded in the West

Oxford and Kidl ington zone in Apri l and the value in the Faringdon Town

in May was 248.2μg/l. The company has conf irmed the need for

maintenance to the distr ibut ion system and in tend to enter into a legal ly

binding agreement to carry out improvement work in ident if ied zones in the

North Oxfordshire area. In two other zones in Oxfordshire (Carterton and

Witney and Deddington and Bicester) , Thames Water’s response to

failures of the iron standard in February and December demonstrated the

need for sections of main to be renovated.

In the Ashford/Staines zone, fol lowing a failure of the iron standard in July,

Veol ia Water Central ident if ied that the property shared a common supply

pipe with a neighbouring property and tap water qual ity at both propert ies

was unsatisfactory with elevated levels of iron and turbidity. The company

replaced the common communication pipe and carr ied out f lushing and a

f ibre scope survey. However, this did not resolve the problem and sections

of an upstream main were ident if ied subsequently as being in need for

rel ining. This work was completed in February 2011 and al l subsequent

samples have been compliant for iron.

Manganese

Manganese was detected in Augus t at a consumer’s tap in the

Northwood/Ruislip zone . Veol ia Water Central ’s investigation l inked this to

a burst main event in the adjoining road. Another manganese failure , in the

Wembley zone in September, was considered to be due to an isolated

Thames reg ion

33

occurrence of mains deposits. The Inspectorate expects companies to take

failures into account in their Distr ibut ion Operation and Maintenance

Strategies (DOMS) and this should result in updating of the part icular

regulatory r isk assessments.

In January, a fai lure of the manganese standard in the Hur lingham zone,

Putney was associated with a failure of the iron standard. Thames Water

identif ied the problem as being conf ined to the supply for a single

commercial property situated at the end of a main. The company put in

place a per iod of regular f lushing and resolut ion of the problem wil l be

conf irmed by diagnostic sampling.

Benzo(a)pyrene

Veolia Water Central detected benzo(a)pyrene at a level of 0.02µg/l in a

consumer ’s tap sample col lected f rom the East Barnet zone during

October. The company’s investigation establ ished that work had recent ly

been carr ied out to remove a pressure reducing valve and replace a

distr ict meter outside the property , therefore the failure was regarded as

an isolated occurrence not indicat ive of a wider problem.

Annex 5 detai ls the legally binding programmes of distr ibut ion

maintenance work scheduled to be completed between now and 2015 to

address cont inuing distr ibut ion qual ity problems in the region.

Drinking water quality events

Water quality events are classif ied into f ive broad categories based on the

init ial company report . The categories are:

Not significant: no further information required by an inspector to assess

the event.

Minor: i t is unl ikely that further information would be required by an

inspector to assess the event .

Significant: a ful l company report may be required to enable an inspector

to assess the event .

Serious: in addit ion to a full company report, the assessment may require

act ion by more than one inspector and a resultant invest igation.

Major: in addit ion to a full company report, the assessment is l ikely to

involve an investigat ion led by senior inspectors requir ing extensive

information gather ing and wide ranging investigat ions.

In 2010, companies in the Thames region notif ied the Inspectorate of

51 events. Table 12 shows how these events were classif ied.


34

Table 12: Water quality events in the region in 2010

Nature of event Risk assessment category (DWI)

Minor/not-signif icant

Signif icant Major/serious

2009 2010 2009 2010 2009 2010

Air in water - - - - - -

Chemical 1 - - - - -

Discoloured water 1 1 2 2 - -

Inadequate t reatment - - - - - -

Loss of suppl ies/poor pressure 11 13 - 2 - -

Microbiological 17 3 4 5 - -

Taste/Odour 7 2 - 1 - 1

Health concern 1 - - 1 - -

Publ ic concern 13 17 1 - - -

Other 5 1 1 2 - -

Region overal l 56 37 8 13 - 1

England and Wales 276 222 141 160 5 9

A summary of the nature, cause and durat ion of each event categorised as

signif icant, serious or major , along with detai ls of the Inspectorate ’s

f indings are set out in Annex 3 . Most events were of relat ively short

durat ion and the company took appropriate act ion at the t ime to inform and

safeguard consumers and other stakeholders. A comparison of 2009

events with those of 2010 shows there were more signif icant , serious and

major events.

The region experienced one serious chemical contaminat ion event in 2010

which resulted in drinking water with an object ionable taste and odour

being supplied to close to two mill ion people l i ving in North London.

Wider learning points f rom event investigations in the region in 2010 are

highl ighted by the following cases:

Abnormal taste and odour due to raw water contamination

This event potent ially af fected a populat ion of two mil l ion people

l iving in the area of north London suppl ied by Thames Water’s

Coppermills works. An object ionable taste and odour reported by

consumers was traced to raw water abstracted f rom the River Lee

and stored in the Will iam Gir l ing and King George V reservoirs. An

alternative raw water supply can be provided from the River Thames

via an abstract ion point south west of London and the Thames-Lee

tunnel. This raw water f rom the Will iam Gir l ing reservoir is also

transferred to Essex and Suffolk Water’s Chigwell works a nd a

further half a mil l ion customers of that company were pote ntially

affected (see the Drinking water qual ity events sect ion of the

Eastern region report).

Thames reg ion

35

Customer complaints of unusual tastes and odours were recorded by

Thames Water f rom mid-January through to early March. Once the

company made the l ink between these complaints and Coppermil ls

works, abstract ion f rom the River Lee was stopped and the volume

of raw water being transferred via the Thames -Lee tunnel increased.

The cause of the unusual taste and odour was traced to the

chemicals 2-ethyl-5,5-dimethyl-1,3-dioxane (2-EDD) and 2-ethyl-4-

methyl-1,3-dioxolane (2-EMD). These substances belong to a class

of compounds which are by-products of resin manufacturing . They

are documented as being responsible for a small number of taste

and odour events around the wor ld, including one which occurred in

the UK af fect ing the River Wem and customers of Severn Trent

Water in 1994. A characterist ic of these substances is that they have

a very low taste and odour threshold (0.01µg/l for 2-EDD) and so

can be detected by consumers at levels wel l below those which may

pose a potent ial r isk to health. Maximum values reported dur ing the

event were 0.026µg/l of 2-EDD and 0.186µg/l of 2-EMD well below

the HPA health-based action levels of 2 ,500µg/l 2-EDD and

1,400µg/l 2-EMD.

The source of these chemicals was tracked to a commercial waste

stream at Thames Water’s Rye Meads Sewage Treatment Works

which discharges into the River Lee. Discharges f rom this waste

stream were stopped. In total , Thames Water received 1,114

consumer reports between 3 January and 21 March. There were an

addit ional 97 reports from customers of Essex and Suffolk Water

between 3 February and 11 March . Many of these were conf irmed by

analysis of samples col lected by the compan ies f rom consumers’

taps. As part of the Inspectorate’s invest igation of this event, around

1,000 customers of both companies were sent a questionnaire and

28 of those who returned a questionnaire were subsequent ly vis ited

and given the opportunity to provide statements about their

exper iences to inspectors. A confounding factor in the assessment

of the consumer aspects of this event was a ‘winter vomit ing bug’

outbreak in North London that was ongoing at the t ime and

conf irmed by local health professionals , at North East and North

Central London Health Protect ion Unit , as not related to water

suppl ies.

This event highl ights the need for al l companies to review risks

relat ing to the management of these chemicals in the catchments of

water works, part icularly in relat ion to commercial trade waste

arrangements at upstream sewage works . The event also highl ighted

r isks in relat ion to bulk supply imports of both raw and treated water

between companies, together with the need for better co-ordination


36

of water qual ity information and controls, effect ive and t imely

communications and also prompt diagnosis of the potential

signif icance of taste and odour contacts from consumers.

The Inspectorate expects companies to further develop their

regulatory r isk assessments and mit igat ion measures to take

account of the r isk that customer cal l handl ing arrangements are not

suff icient ly sensit ive in large supply areas serving densely populated

urban areas (and also wherever there are complex supply

arrangements) to facil i tate prompt diagnosis of rare , but potentially

important, water quality r isks.

Loss of supplies due to a hydrant repair on a 300mm main

In January, damage sustained whi le repair ing a leak to a hydrant

located on a 300mm main resulted in depressurisat ion of the

distr ibut ion system in the Cast lewood area of Well ing. Approximately

500 consumer contacts regarding no water/ low pressure were

received by Thames Water. Erith Booster Stat ion, which suppl ies the

local ity, had been shutdown to enable the repair . The damaged

hydrant was replaced and the main returned to supply , however, this

resulted in a further 29 consumers report ing mainly white water, but

also brown discolourat ion and part ic les. In response, the company

carr ied out a programme of mains-f lushing.

The Inspectorate cr it ic ised the company for not taking samples

representat ive of the area affected, most samples were f rom one

location and only two fell within the af fected area. Companies are

reminded that it is a regulatory duty to carry out an adequate

investigation of the extent of any contaminat ion aris ing f rom

operat ional events.

When assessing this event , the Inspectorate noted that only seven

out of ten operators working on this event possessed water hygiene

cards to demonstrate that they had received appropr iate training in

the essential public health safeguards to be followed when working

on distr ibut ion systems. Companies are reminded that al l relevant

staff must carry val id water hygiene cards at al l t imes and suitable

systems must be in place to ident ify individuals and ensure they

receive refresher training before their card expires.

Taste and odour due to planned work

In January, Veol ia Water Central received four consumer contacts

about an object ionable taste and odour f rom the hamlet of Lit t lebury

Green, Saffron Walden. In the week before, the company had been

investigating intermit tent low pressures in the area and f lushing

mains. When responding to the water qual ity complaints the init ia l

Thames reg ion

37

f lushing was ineffect ive because of a shut valve which the company

failed to identify. The Inspectorate was crit ical that it took a

subsequent review of the f lushing regime before the company

recognised that the valve arrangements had not been optimised prior

to carrying out the remedia l work. Sampling during the event

identif ied the presence of polycycl ic aromatic hydrocarbons ( PAH)

indicating that the complaints were due to the nature and condit ion

of the main and its l ining material. However, the company had no

record of the pipe material and therefore could not be certain as to

the cause. The Inspectorate reminds companies that local ised taste

and odour events caused by the release of standing water f rom

behind shut valves have been well documented. Companies are

reminded that events of this type should lead to a comprehensive

survey of local mains with updat ing of records. Such information

should be taken into account in Distr ibut ion, Operation and

Maintenance Strategies and result in a review of the relevant

regulatory r isk assessment in respect of customer acceptabil i ty , and

act ion plans for long-term mit igat ion should be put in place .

Loss of disinfection

In May, Sutton and East Surrey Water notif ied the Inspectorate of an

event involving the temporary loss of dis infect ion at Woodm ansterne

works. Low chlor ine residual on the contact tank inlet tr iggered an

alarm and the works shut down automat ical ly . The company init ial ly

misdiagnosed the problem as a faulty sample pump and decided to

re-start the works by overriding the shut -down. Init ial ly the chlor ine

concentrat ions showed an improvement , however, the contact tank

readings did not return to normal and the plant was shut down.

Further invest igation ident if ied that the cause of the problem was a

faulty pressure gauge on the chlor ine gas drum changeover unit .

This indicated that the drum was in a healthy condit ion when in fact

it was almost empty. The chlor ine drum was manual ly changed to a

full drum, the contact tank manually dosed and the plant returned to

normal operat ion. The Inspectorate noted that this constituted a

breach of Regulat ion 26 because for a period of about three hours

treatment was not continuously operated in the manner in which it

was designed and this resulted in water leaving the works which did

not meet the company’s dis infect ion cr iter ia. The Inspectorate was

highly crit ical of the misdiagnosis of the problem and the granting of

permission to overr ide the plant without a full understanding of the

cause. Sutton and East Surrey Water took the following act ion to

prevent a recurrence: installat ion of an independent pressure gauge,

dai ly gas stock checks and the procedure for authorising treatment

overrides has been reinforced.


38

The Inspectorate continues to be disappointed to note those

investigations which l imit the abi l i ty of companies to proactively and

adequately reassure themselves of the robustness of act ions during,

in response to, and fol lowing an event to ensure compliance with

Regulat ion 26.

The offence of supplying water unf it for human consumption is und er

considerat ion by the Inspectorate in connection with one event that

occurred in the region in 2010.

Technical audit activity

The Inspectorate has operated a r isk -based approach to technical audit

since 2005. In l ine with better regulat ion principles, no technical audit

takes place without a reason.

The Inspectorate’s tool for generating the technical audit programme loo ks

at the crit ical components of the safe management of drinking water

suppl ies, including information on water quality monitor ing, event

assessments, previous audits, consumer complaints and other relevant

intel l igence. Through this ranking of all relevant water company assets,

procedures and pract ices, inspectors are able to prior it ise and focus their

technical audit work where it wil l have most benef it . The resultant audit

programme for 2010 is summarised in Table 13. The Inspectorate also

carr ied out an audit related to analyt ical malpract ice at a laboratory

operated by Severn Trent Services who analysed samples for Independent

Water Networks and SSE Water in the region.

Table 13: Summary of the Inspectorate ’s technical audits in the region

Site name Audit topic Main f indings from audit

Severn Trent Services – Analyt ical Services Ltd

Br idgend laboratory

Analyt ica l malpract ice

Audi t deemed unsat isfactory – subsequent invest igat ion ongoing

Recommendations were made in respect of inorganic chemical analysis for the water undertakers or the combined l icensees in fai l ing to meet their obl igat ions under Regulat ions 16 and 34 for analys is of water samples and, in part icu lar , der ived analyt ica l data, competency, retent ion of appropr iate records and for the appropr iate t ime us ing suitable equipment.

cont inued

Thames reg ion

39

Site name Audit topic Main f indings from audit

Br idgend laboratory

(cont inued)

Analyt ica l malpract ice

The Inspectorate reminded companies that i t is the duty of the water under taker or the combined l icensee to ensure they are compl iant and th is cannot be deferred to a th ird party laboratory.

Recommendations were made to ensure that the provis ion of informat ion as part of the companies regulatory dut ies must be demonstrated to be a t rue representat ion of a robust and an actual analyt ica l procedure.

Recommendations were made for the future avoidance of breaches of the regulat ions requir ing the laboratory, through the dut ies of the s tatutory under takers, to implement and mainta in a system of operat ional management cover ing a number of areas, but inc luding robust, t imely, ef fect ive and responsive use of qual i t y systems, capac ity managemen t and independent bus iness and qual i t y object ives.

Enforcement act ion taken in respect of e ight companies us ing the laboratory for chemical analys is of regulatory dr ink ing water samples.

Ful l deta i ls are to be provided in the form of a publ ished audi t repor t and wi l l be avai lable on the Inspectorate ’s website on complet ion of the invest igat ion.

Thames Water

Beckton Gateway desal inat ion

Process control

General ly sat isfac tory

Recommendations were made concerning the need for a p i lo t s tudy to secure customer acceptabi l i t y through re -mineral isat ion of desal inated water pr ior to supply .

Recommendations were made to ensure s i te manuals and procedures are completed and in p lace before the s i te goes into supply .

Veolia Water Central

Chishi l l serv ice reservoir

Site integr i ty and sampl ing faci l i t ies

General ly sat isfac tory

The management of water qual i t y and turnover could be improved and therefore a recommendat ion was made that the company reviews and improves i ts turnover pol icy at th is s i te to preserve water qual i t y and sat isfy i tse lf that chlor ine res iduals are appropr iate for th is area of supply.


40

Public confidence in drinking water quality

Consumer contacts to water companies

When consumers have a question or a concern about dr inking water

quality their f irst point of contact is the water company. Al l companies

record these contacts using def init ions agreed with the Inspectorate.

The Inspectorate has been col lect ing consumer contact information f rom

the industry for a number of years. Figure 14 i l lustrates t he improving

picture in England, with a 29% reduction over f ive years in the number of

consumers report ing a problem with their tap water (now about 98,000

compared to 138,000 in 2006). Over the same t ime frame, the Thames

region has seen a 27% fall in con tacts to about 10,700 in 2010 compared

to approximately 17,000 in 2006. In 2010, one out of every 10 contacts in

England were f rom people l iving or working in the Thames region. In

comparison to other regions, the Thames region now has the lowest

contact rate (0.9 per 1,000 populat ion).

Figure 14: Total consumer contacts for appearance, taste and odour,

i l lness 2006-2010

0

20,000

40,000

60,000

80,000

100,000

120,000

140,000

160,000

2006 2007 2008 2009 2010

Co

nsu

me

r co

nta

cts

Thames region

Other regions

Looking in more detail at the information, the most commonly reported

concern is white water caused by entrained air (see Figure 15). I n 2010,

the previous improving trend in this type of contact level led of f , because

while the f igures for Thames Water and Sutton and East Surrey Water

improved again, this was of fset by a r ise in white water contacts recorded

by Veol ia Water Central. The Inspectorate expects companies to use

contact data to analyse events in the network to improve operational

pract ices and thereby minimise the impact on consumers.

Thames reg ion

41

Figure 15: Numbers of consumer contacts 2006-2010

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

2006 2007 2008 2009 2010

Co

nsu

mer

co

nta

cts Total (appearance/taste

and odour/illness)

White water due entrained to air

Black, brown or orange water

Total taste or odour

The downward trend in the number of consum ers notifying companies

about black, brown or orange water cont inued in 2010 and the

improvement was mainly in the areas served by Thames Water and Veol ia

Water Central . Maps in the Maintaining water quality in distr ibut ion sect ion

i l lustrate, on a zone-by-zone basis, the progress made since 2007 . This is

clearly vis ible across the region with only two areas (north of Haslemere

and south of Harlow) now exhibit ing more than two contacts per 1,000

populat ion in 2010.

Taste and odour reports decl ined overall i n 2010, mainly due to a fall in

chlorine-related tastes and odours by Thames Water, Sutton and East

Surrey Water and Veol ia Water Central . However, this improvement was

part ial ly of fset by a r ise in contacts categorised as other. The Inspectorate

has had to remind companies in 2010 of the importance of recording the

nature of tastes and odours reported in laboratory tests , and it is equal ly

important to record a descript ion in relat ion to consumer taste and odour

reports.

Consumer complaints to the Inspectorate

When the response of a company to a consumer contact about drinking

water qual ity fails to provide the necessary reassurance or remedy then

the consumer may contact the Inspectorate for advice. In 2010, there were

25 consumers suf f iciently dissatis f ied with the water company’s init ia l

response to their complaint to raise the matter further with the

Inspectorate. The reasons for contact ing the Inspectorate are provided in

Table 16.


42

Table 16: Contacts from consumers received by the Drinking

Water Inspectorate

Category Number of contacts

Appearance 4

Taste and odour 17

Report of i l lness 3

Water qual i t y concern 1

Number of contacts to DWI f rom consumers by company.

TMS (23), VCE (2)

Categor ies a re as def ined in In format ion Let ter 1 /2006

Figure 17 depicts the numbers of complaints received by the Inspectorate

f rom consumers in the region since 2002 in the context of the total

complaints received f rom consumers in England and Wales. The graph

i l lustrates a general ly improving trend in the Thames region since 2005,

which follows that for the industry as a whole. Also, Figure 17 i l lustrates

the adverse impact that events have on publ ic conf idence as evidenced by

the sharp r ise in complaints to the Inspectorate f rom Thames Water

customers in 2010 which related to the taste and odour event in north

London (see the Drinking water quality events sect ion).

Figure 17: Complaints received by DWI from 2002 to 2010

0

20

40

60

80

100

120

140

160

180

2002 2003 2004 2005 2006 2007 2008 2009 2010

Co

nsu

me

r co

nta

cts

Thames region

Other regions

Abnormal taste and odour due to raw water contamination

Between February and March, 17 consumers f rom the North London supply

area of Thames Water contacted the Inspectorate about an unpleasant

taste and odour in their water supply. The f irst of these contacts to the

Thames reg ion

43

Inspectorate was on 10 February dur ing a t ime period when there had

been a sharp r ise in similar complaints to the water company from

3 February onwards. This part icular consumer contacted the Inspectorate

because Thames Water had dismissed the information he had provided to

the company. The consumer had f irst not iced the problem in mid-January.

When contacted, the Inspectorate was aware of the taste and odour event

originating f rom Coppermills works because this had been noti f ied to the

Inspectorate on the previous day (see the Drinking water quality events

section). The Inspectorate contacted Thames Water to make sure that the

company investigation was communicating with this and similar consumers

who had reported a problem to them before the event had been ident if ied.

Thames Water received 119 consumer contacts about an object ionable

taste and odour between 3 January and 2 February cover ing 29 of the

42 supply zones suppl ied f rom Coppermil ls works. However, the company

failed to proactively diagnose a wider problem because these early

contacts equated to only two or three per day. Consumer complaints are

of ten the f irst or only sign of a serious event and are thus a valuable

source of information to be monitored on a continuous basis . I t is

essent ial , therefore, that companies set tr igger values appropriate to the

supply circumstances. For example, in large urban areas many zones may

receive water f rom a common source , therefore a generic zone-by-zone

tr igger value is not suff icient ly sensit ive or appropr iate.

A total of 1,114 contacts were received by Thames Water in relat ion to thi s

event between 3 January and 21 March. Many of these contacts arose

because the company had been tell ing consumers over the phone that

their water was safe to drink while at the same t ime the media was

report ing chemical contamination of the water source with industr ial

chemicals which the company subsequently conf irmed in a press release .

Consumers therefore felt that the company was not being truthful . The loss

of trust in the company by its customers was exemplif ied by the react ion of

the consumer in th is case. He subsequent ly spoke on several occasions to

the Inspectorate, instead of the company, to obtain information .


44

Planned drinking water quality improvements

Securing safe, clean drinking water through the application of a

risk-based approach to regulation

The publ icat ion of Drinking water 2010 marks an important milestone in the

history of drinking water regulat ion , namely the 20-year anniversary of

implementat ion by government of the EU Drinking Water Direct ive.

I t records how the regulatory regime has been applied successfully and

improved upon since. In part icular, the regulatory f ramework now goes

beyond rect ifying def ic iencies in drinking water qual ity by convert ing two

decades of essential investment in water treatment and distr ibut ion int o

sustainable improved drinking water suppl ies through operator r isk

assessment and t imely preventat ive act ion incent ivised by independent

oversight and f irm, but fair , sanctions.

Figure 18: The percentage of tests fail ing the standards from

1991 to 2010

0

0.5

1

1.5

2

2.5

Pe

rce

nta

ge o

f sa

mp

les fa

ilin

g in

zo

ne

s

England and Wales Scotland Northern Ireland

The purpose of drinking water regulat ion is to secure safe , clean drinking

water for all and this outcome is measured object ively by the Inspectorate

using ver if ied scient i f ic data (Figure 18) alongside data to conf irm the

benef it in the form of consumer reports about tap water qual ity (Figure 19).

These outputs are measured at the tap and therefore provide ver if icat ion

of the eff icacy of all the historical investment and operational management

act ions taken at every point throughout a supply system from source to

tap.

Thames reg ion

45

Figure 19: The total amount of consumer contacts for appearance,

taste, odour and il lness from 2006 to 2010

100,000

110,000

120,000

130,000

140,000

150,000

160,000

2006 2007 2008 2009 2010

Co

nsu

me

r co

nta

cts

The principal regulatory enforcement tool that has enabled this

improvement in dr ink ing water qual ity has been the putt ing in place of

legal ly binding programmes of work to address clear ly ident if ied and

specif ic def iciencies by the Inspectorate. Over 20 years these

‘undertakings’ , given under Section 19 of the Water Industry Act 1991 ,

have enabled water companies to design and del iver technically

appropr iate asset improvement schemes. An undertaking comprises a

schedule of sequential remedial steps; typical ly these wil l be an

investigation, followed by changes to the operation of a treatment

works/supply system or the instal lat ion of new treatment equipment at a

works or the renovat ion/replacement/cleaning of water mains. The

schedules set del ivery dates for each milestone step with report ing

requirements for progress monitoring and demonstrat ion of benef it , i .e.

that the outcome required has been achieved.

In 2004, the World Health Organisation (WHO) published the water safety

plan approach as the most effect ive means of securing a suff icient supply

of safe, clean dr inking water for al l. In 2005, the Inspectorate adopted the

water safety plan approach as its strategic pol icy for developing the

regulatory regime for drinking water f irst introduced by Parl iament in

England and Wales in 1990. In 2007, the drinking water regulat ions in

England and Wales were amended to formally embed thi s r isk-based

approach into the legal f ramework.

These amendments included provision for Regulat ion 28(4) Notices, a new

enforcement tool that is now convert ing two decades of investment in

improvement into sustainable supplies of safe , clean dr inking water.

These Not ices set out the steps that are necessary to mit igate


46

unacceptable residual r isks. A Notice typical ly specif ies the fol lowing types

of act ions: addit ional improvements or maintenance, regular reviews and

audits of operational controls, condit i ons under which use of a supply is

prohibited, management and other information requirements and report ing.

The principal dif ference between the two enforcement tools is that

undertakings are generally fai lure dr iven , whereas Not ices are r isk-based

and preventat ive. Undertakings are used where a fai lure has occurred and

is considered l ikely to recur, identif ied usual ly through the audit act ivity of

the Inspectorate, or as part of a water company’s business planning

processes. Not ices, by contrast, ar ise out of a process of continuous r isk

assessment carr ied out by water companies where the Inspectorate

acknowledges the manner by which ident if ied r isks are being mit igated and

control led. I f necessary for the protect ion of public health, certain controls

or remedial act ions can be audited, imposed or made mandatory. Both

enforcement tools serve as an incentive to improve drinking water suppl ies

and to protect consumers. Furthermore, as a consequence of putt ing r isk

assessment at the heart of the new enforcement tool, the extent to which

r isk management and r isk prevent ion are becoming embedded in the

industry can be measured object ively by the recording of acknowledge d

actions to mit igate r isk.

Across the industry, there are currently 469 mandatory schemes

documented in the report (Annex 4) where enforcement has been used to

improve those few water suppl ies that continue to fail to meet drinking

water standards (undertakings) or to mit igate previously unrecognised

r isks which pose a potential danger to human hea lth (Not ices). In addit ion,

there are 516 other preventat ive act ions identif ied by water companies

through r isk assessment and acknowledged by the Inspectorate. Table 20

ref lects the progress of the industry in delivering these acknowledged

preventat ive act ions. Together all these data can be used to demonstrate

the extent to which a proactive preventat ive approach to the management

of drinking water qual ity has become embedded in water companies as a

result of the switch to mandatory r isk management. For e xample, more

than half (52%) of the 985 improvement act ions identif ied as necessary at

the end of 2008 are being del ivered voluntari ly, without the need for

enforcement act ion by the Inspectorate.

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Table 20: Acknowledged actions to sustain safe, clean drinking water

Region Addit ional acknowledged act ions to mit igate risk

(as at Dec 2008)

Acknowledged act ions completed (as at Dec 2010)

Centra l 0 0

Eastern 10 1

Nor thern 44 15

Southern 51 20

Thames 62 36

Western 38 25

Wales 311 35

Total 516 132 Note: The Cent ra l reg ion f i gures do not inc lude Dŵr Cymru W elsh W ater . The f igures fo r the Northe rn reg ion do not inc l ude Dee Va l ley W ater . The f igures for W ales do not i nc lude Severn Trent W ater .

Mitigating risks at source through catchment management

An important element of the r isk assessment process carr ied out under the

Regulat ions is the character isat ion of hazards within catchments,

determining where these pose a r isk to the quality of a specif ic drinking

water supply and how they wi l l be mit iga ted through actions in the

catchment to protect or improve raw water quality. Ar is ing out of this work

a number of companies now have catchment management schemes as a

component of undertakings and catchment management act ivit ies may be

specif ied in Not ices or in acknowledged action plans. The direct benef its of

catchment management are the potential for removing the need for costly

provision, or replacement, of water treatment or for reducing operat ional

expenditure in relat ion to treatment already in plac e. These schemes also

provide wider benef its where they result in improvements to the natural

environment.

A typical example is a scheme or act ion plan where the water company

commits to carrying out an invest igation to pinpoint the source of specif ic

contaminants (such as nitrate, one or more pestic ide s, or colour as a

precursor of dis infect ion by-products) by sett ing up a working partnership

with local stakeholders such as the Environment Agency, farmers, land

managers and agronomists, for example, to alter the way in which a

product is being appl ied to land. The company wil l carry out targeted raw

water monitoring and contr ibute other resources to set up and facil i tate the

work of the partnership. Table 21 summarises the catchment management

work in the Thames region in relat ion to the drinking water qual ity

parameters.


48

Table 21: Catchment management activities in the region

Company Treatment works where

regulated catchment management is in place

Risk being mit igated


0 N/A

SSE W ater 3 Metaldehyde (3)

Sut ton and East Surrey W ater

1 Metaldehyde (1)

Thames Water 15

Chlorto luron (1) Isoproturon, bentazone, atrazine and s imazine (1) Metaldehyde (13)


9 Metaldehyde (9)

Region overal l 28

Chlorto luron (1) Isoproturon, bentazone, atrazine and s imazine (1) Metaldehyde (26)

Note: Independent W ater Networks a lso supp l y wate r i n the Eas te rn reg ion where they have two p lans in p lace f or Meta ldehyde.

For further information on the Water Supply (Water Qual ity) Reg ulat ions

2000, or the microbiological and chemical parameters covered by the

regulat ions please refer to the DWI website (www.dwi.gov.uk) .

I f you have a need for more specif ic information than that on our website,

please contact us on the DWI enquiry l ine: 030 0068 6400.

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Annex 1

Further sources of information

The publ icat ion Drinking water 2010 comprises the regional reports for

England and a report covering Wales. There are six regional reports for

England (Central, Eastern, Northern, Southern, Thames and Western) and

one for Wales ( in two languages). Each report presents information f rom

2010 under the fol lowing headings:

Introduction to the report.

Water supply arrangements.

Drinking water qual ity test ing.

Drinking water qual ity results.

Risk assessments.

Drinking water qual ity events.

Technical audit act iv ity.

Publ ic conf idence in drinking water qual ity.

There are also separate reports covering private water supplies, one

cover ing England and one covering Wales.

The reports and other content are publ ished on the DWI website

(www.dwi.gov.uk).

Content of the CD

The CD suppl ied with the printed report holds all of the above content and

addit ional ly it contains:

Water company look-up tables

These summarise al l the results of water company monitor ing in 2010.

They provide information on:

what was tested;

how many tests were performed;

the range of the results of test ing; and

how many tests failed to meet the standards.

Significant drinking water quality events in England and

Wales 2010

To promote shared learning, the Inspectorate has compiled a l ist of al l

events that occurred in 2010 which i l lustrate the nature and cause of each

event, the main act ions by the company and f indings f rom the inspectors’

assessments. Relevant content f rom this overal l l ist is contained in an

annex to each regional report.


50

Annex 2 Glossary and description of standards

These def init ions wil l assist the understanding of the report where

technical terms have been used.

µg/l microgram per l i t re (one mil l ionth o f a gram per l i t re) .

1,2-Dichloroethane is a solvent that may be found in groundwater in the v ic in ity of industr ia l s i tes . W here necessary i t can be removed by spec ia l water treatment . A European health-based standard of 3μg/ l appl ies.

Acrylamide European heal th-based s tandard. A monomer is not normal ly found in dr ink ing water . I t is produced in the manufacture of polyacrylamides occas ional ly used in water treatment . I ts presence in dr ink ing water is l im ited by control of the product spec if icat ion. Standard is 0.1µg/ l .

Aesthetic assoc iated wi th the senses of taste, smel l and s ight .

Aggressive

a term used to indicate that the water has a tendency to d issolve copper (and other metals) f rom the inner surface of a p ipe or water f i t t ing such as a tap.

Alkali

a solut ion conta in ing an excess of f ree hydroxyl ions, wi th a pH greater than seven.

Aluminium occurs natura l ly in some source waters . I t is removed f rom dr ink ing water by convent ional water t reatment (coagu lat ion and f i l t ra t ion) . Aluminium sulphate and polyaluminium chlor ide may be used as water treatment chemicals at some water treatment works. A nat ional standard of 200μg/ l appl ies.

Ammonium salts are natura l ly present in trace amounts in most waters. Their presence might indicate contaminat ion of sanitary s ignif icance and they interfere wi th the operat ion of the dis infect ion process. An indicator parameter wi th a guide value of 0.5mg/ l.

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Analytical qual ity control (AQC)

the method used to ensure that laboratory analys is methods are performing correct ly.

Antimony is rare ly found in dr ink ing water . Trace amounts can be der ived f rom brass tap f i t t ings and solders. A European heal th -based standard of 5μg/ l appl ies.

Aquifer water -conta ining underground s trata.

Arsenic occurs natura l ly in only a few sources of groundwater. Spec if ic water t reatment is required to remove i t . A European health -based s tandard of 10μg/l appl ies .

Authorised departure author isat ion for a water company to temporar i ly supply water exceeding a dr ink ing water standard, granted by the author i t ies only when there is no r isk to human health.

Benzene is present in petro l. I t is not found in dr ink ing water , but i t can migrate thr ough underground p last ic water p ipes i f petro l is spi l t in the v ic in ity. Some bot t led waters and sof t dr inks which include sodium benzoate as an ingredient have been repor ted as conta in ing benzene. A European health-based standard of 1μg/ l appl ies .

Benzo(a)pyrene is one of several compounds known as polycyc l ic aromat ic hydrocarbons (PAHs) . Their source in dr ink ing water is as a resul t of deter iorat ion of coal tar , which many years ago was used to l ine water pipes. Due to extens ive water mains refurb ishment and renewal i t is now rare to detect th is substance in dr ink ing water. A European health-based standard of 0.01μg/ l appl ies.

Boron in surface water sources comes f rom industr ia l d ischarges or f rom detergents in treated sewage ef f luents . The very low concentrat ions found in some dr ink ing waters are not a concern to publ ic heal th. A European heal th -based standard of 1mg/ l appl ies .


52

Bromate can be formed dur ing d is infect ion of dr ink ing water through a react ion between natura l ly occurr ing bromide and strong ox idants (usual ly ozone). I t may be generated in the manufacture of sodium hypochlor i te d is infectant . Except ional ly, groundwater beneath an industr ia l s i te can become contaminated wi th bromate. A European health-based standard of 10μg/ l appl ies.

Bulk supply water suppl ied in bulk , usual ly in treated form, f rom one water company to another.

Cadmium is rare ly detected in dr ink ing water and trace amounts are usual ly due to d issolut ion of impur it ies f rom plumbing f i t t ings. A European health-based s tandard of 5μg/ l appl ies .

Catchment

when used in connect ion wi th water , the catchment is the area dra ined by a r iver or water body.

Chloramination the process of generat ing a chloramine d is infectant res idual in water leaving a t reatment works.

Chloramine a substance formed by a react ion between chlor ine and ammonia, used as a d is infectant in d istr ibut ion systems because of i ts long - las t ing propert ies compared to chlor ine.

Chloride is a component of common sal t . I t may occur i n water natura l ly, but i t may also be present due to local use of de- ic ing salt or sal ine intrus ion. An indicator parameter with a guide value of 250mg/l .

Chlorine residual the small amount of ch lor ine or chloramines present in dr ink ing water to mainta in i ts qual i t y as i t passes through the water company’s network of p ipes and household p lumbing.

Chromium is not present in dr ink ing water . A European health-based s tandard of 50μg/ l appl ies.

Clostridium perfringens is a spore-forming bacter ium that is present in the gut of warm-blooded animals . The spores can survive d is infect ion. The presence of spores in dr ink ing water indicates h is tor ic contaminat ion that requires invest igat ion. The standard is 0 per 100ml.

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53

Coagulat ion a process employed dur ing dr ink ing water treatment to ass ist wi th the removal of par t icu late matter.

Coliform bacteria

are widely d istr ibuted in the environment of ten as a result of human or animal ac t ivi ty, but some grow on p lant mat ter . Their presence in a water supply indicates a need to invest igate the integr i ty of the water supply system. The s tandard is 0 per 100ml.

Colony counts are general techniques for detect ing a wide range of bacter ia, the types and numbers being dependent on the condit ions of the test . These counts , i f done regular ly, can help to inform water management, but they have no direct heal th s ignif icance. The s tandard is ‘no abnormal change’.

Colour occurs natura l ly in upland water sources. I t is removed by convent ional water treatment. A nat ional standard of 20mg/ l on the Plat inum/Cobalt (Pt /Co) scale appl ies .

Communicat ion pipe the connect ion f rom the water main to the consumer’s property boundary.

Compliance assessment a compar ison made by the Inspectorate of data gathered by water companies against standards and other regulatory requirements .

Compound a compound cons ists of two or more e lements in chemical combinat ion.

Concessionary supplies histor ica l f ree suppl ies of water for a householder , es tabl ished when a company wanted to lay mains across land and the landowner might agree, subject to a permiss ion, to take a supply of water f rom the main.

Conduct ivity is a non-spec if ic measure of the amount of natura l d issolved inorganic substances in source waters . An indicator parameter wi th a guide value of 2,500µS/cm.

Contact tank a tank, normal ly s i tuated on a treatment works s ite, which forms par t of the d is infect ion process. A d is infectant chemical (normal ly chlor ine) is dosed into the water as i t f lows into the tank. The per iod of t ime that the water takes to f low through the tank a l lows suf f ic ient ‘contact ’ t ime for the chemical to k i l l , or deact ivate, any v iruses or pathogenic organisms that may be present in the water.


54

Contravent ion a breach of a regulatory requirement.

Copper in dr ink ing water comes mostly f rom copper p ipes and f i t t ings in households. In general, water sources are not aggress ive towards copper, but problems very occasional ly occur on new hous ing estates. These ‘b lue water ’ events can be avoided by good p lumbing pr act ices. A European health-based standard of 2mg/l appl ies .

Cryptosporidium is a paras ite that causes severe gastroenter i t is and can survive d is infect ion. In the UK, cont inuous monitor ing is under taken at works c lassif ied by the company as being at s ignif icant r isk .

Cyanide is not present in dr ink ing water . A European health-based s tandard of 50μg/ l appl ies.

Dead leg refers to a p iece of p ip ing which is stopped of f at one end, but is connected to the supply at the other end and can result in stagnant water in the p ipework.

Distribution systems a water company’s network of mains, p ipes, pumping stat ions and service reservoirs through which treated water is conveyed to consumers.

Drinking water standards the prescr ibed concentrat ions or values l is ted in regulat ions.

EC Drinking Water Direct ive Counci l Direct ive 98/83/EC December 1998 – set t ing out dr ink ing water standards to be appl ied in member states.

Enforcement act ion the means, as set out in the W ater Act 1989 and consol idated into the W ater Industry Act 1991, by which the Secretary of State requires a water company to comply w i th certa in regulatory requirements.

Enterococci see Escher ichia col i .

Environment Agency the Environment Agency is respons ib le for mainta in ing or improving the qual i t y of f resh, marine, surface and underground water in England and W ales.

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55

Epichlorohydrin can be found in trace amounts in polyamine water t reatment chemicals. I ts presence in dr ink ing water is l im ited by contro l of the product spec if icat ion. A European heal th -based standard of 0.1μg/ l appl ies.

Epidemiology a process of s tudying the d istr ibut ion of cases of d isease wi thin a populat ion in re lat ion to exposure to poss ible sources of the infect ion, wi th a v iew to establ ish ing the actual source of the infect ion.

Escherichia col i and Enterococci

are bacter ia present in the gut of warm -blooded animals. They should not be present in dr ink ing water and, i f present , immediate act ion is required to ident i fy and remove any source of faecal contaminat ion that is found. The standard is 0 per 100ml.

Event

water companies have to inform the Inspectorate about occas ions when water qual i t y or suf f ic iency is af fected or when publ ic conf idence in dr ink ing water qual i ty may be impacted. The Inspectorate refer to these ins tances as ‘Events ’ .

Filt ration the separat ion of suspended par t icu late matter f rom a f lu id.

Fluoride occurs natura l ly in many water sources, espec ial ly groundwater. I t cannot be removed by convent ional water treatment so h igh levels must be reduced by b lending wi th another low f luor ide water source. Some water companies are required by the local heal th author i ty to f luor idate water supplies as a protect ion against tooth decay. The dr ink ing water standard ensures levels are safe in e ither c ircumstance. Fluor idat ion of water is a Depar tment of Health pol icy. A European health -based s tandard of 1.5mg/ l appl ies.

Geosmin a substance produced by the growth of a lgae, normal ly in surface waters which g ives r ise to a character is t ic ‘ear thy’ or ‘musty’ taste or odour.

Granular activated carbon an adsorbent f i l t ra t ion media used to remove trace organic compounds f rom water .

Groundwater water f rom aquifers or other underground sources.


56

Hydrogen Ion

(pH)

gives an indicat ion of the degree of ac id i ty of the water . A pH of 7 is neutra l; va lues below 7 are ac id ic and values above 7 are a lkal ine. A low pH water may result in p ipe corros ion. This is corrected by adding an alkal i dur ing water t reatment. A specif icat ion of between 6.5 and 9.5 appl ies .

Improvement programmes water company improvement works, these are legal ly b inding on the company and each programme wi l l remedy an actual or potent ia l breach of a dr ink ing water s tandard wi th in a spec if ied t ime per iod.

Indicator organism an organism which indicates the presence of contaminat ion and hence the poss ib le presence of pathogens.

Indicator parameter something that is measured to check that control measures, such as water treatment , are work ing ef fect ive ly.

Information Letter formal guidance to water companies g iven by the Inspectorate and publ ished on the Inspectorate ’s webs ite at www.dwi.gov.uk

Inspectorate The Dr ink ing W ater Inspectorate.

Iron is present natura l ly in many water sources. I t is removed by water treatment . Some i ron compounds are used as water t reatment chemicals. However, the commonest source of iron in dr ink ing water is corros ion of iron water mains. A nat ional s tandard of 200μg/l appl ies .

Lead very occasional ly occurs natura l ly in raw waters, but the usual reason for i ts presence in dr ink i ng water is p lumbing in o lder propert ies. I f the water supply has a tendency to d issolve lead then water companies treat the water to reduce consumer exposure. The permanent remedy is for householders to remove lead p ipes and f i t t ings. A European heal th -based standard of 25μg/ l appl ies, but 10μg/l wi l l apply f rom 25 December 2013 onwards.

m3/d cubic metre per day.

Manganese is present natura l ly in many sources and is usual ly removed dur ing treatment . A nat ional standard of 50μg/ l appl ies .

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Mean zonal compliance percentage

a measure of compl iance wi th dr ink ing water standards introduced by the Inspectorate in 2004.

Mercury is not found in sources of dr ink ing water. A European health-based standard of 1μg/ l appl ies.

mg/l mil l igram per l i t re (one thousandth of a gr am per l i t re) .

Microbiological assoc iated wi th the study of microbes.

Ml/d megal i tre per day (one Ml/d is equivalent to 1,000 m

3/d , or to 220,000 gal lon/d) .

Nickel occurs natura l ly in some groundwater and where necessary spec ia l treatment can be i nsta l led to remove i t . Another source of nickel in dr ink ing water is the coat ings on modern taps and other p lumbing f i t t ings. A European health -based standard of 20μg/ l appl ies .

Nitrate occurs natura l ly in a l l source waters a l though h igher concentrat ions tend to occur where fert i l isers are used on the land. Nitrate can be removed by ion exchange water treatment or through b lending wi th other low ni trate sources. A European health-based standard of 50mg/ l appl ies .

Nitrite is somet imes produced as a by-product when chloramine is used as the essent ia l residual d is infectant in a publ ic water supply. Chloramine is the res idual d is infectant of choice in large d is tr ibut ions systems because i t is more stable and long- last ing. Carefu l operat ion of the d is infect ion process ensures levels of ni tr i te are kept below the standard. A European health -based s tandard of 0.5mg/l appl ies.

Notice

an ins truct ion served by the Secre tary of State ( in the case of water suppl ies , the Chief Inspector of W ater) requir ing spec if ic act ions to be taken by the rec ip ient wi th in a spec if ied t imescale.

Odour can ar ise as a consequence of natura l processes in surface waters, par t icular ly betwee n late spr ing and ear ly autumn. W ater treatment with act ivated carbon or ozone wi l l remove natura l substances caus ing taste. The s tandard relates to the evaluat ions of a panel of people assessing samples in the laboratory.


58

Ofwat the water industry’s economic regulator .

Oocyst the res istant form in which Cryptospor id ium occurs in the environment, and which is capable of caus ing infect ion.

Organoleptic character is t ics of a substance as detected by our senses, for example taste, odour or colour.

Ozone process (ozonation) the appl icat ion of ozone gas in dr ink ing water t reatment.

Parameters the substances, organisms and propert ies l is ted in Schedule 2 and Regulat ion 3 of the regulat ions. Parameter def in it ions can be found further on in th is annex.

Pathogen an organism which can infect humans and cause d isease.

PCV see ‘Prescr ibed concentrat ion or value’ .

Periodic review the economic regulator ’s process of sett ing water pr ices.

Pest icides any fungic ide, herbic ide, insect ic ide or re lated product (excluding medic ines) used for the control of pests or d iseases.

Pest icides – organochlorine compounds (aldrin, dieldrin, heptachlor, heptachlor epoxide)

are no longer used in the UK because they are pers is tent in the environment. They are not fo und in dr ink ing water . A European chemical standard of 0.03μg/ l for each compound applies .

Pest icides – other than organochlorine compounds

is a d iverse and large group of organic compounds used as weed k i l lers, insect ic ides and fungic ides. Many water sources conta in traces of one or more pest ic ides as a resul t of both agr icu ltura l and non-agr icu l tura l uses, main ly on crops and for weed contro l on h ighways and in gardens. Where needed, water companies have insta l led water treatment (act ivated carbon and ozone) so that pest ic ides are not found in dr ink ing water . W ater companies must test for those pest ic ides used widely in their area of supply. Pest ic ide monitor ing thus var ies according to r isk . A European chemical standard of 0.1μg/l for each indiv idual substance and 0.5μg/ l for the tota l of a l l pest ic ides appl ies .

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Phosphate dosing t reatment of water that resul ts in a protect ive f i lm bui ld ing up on the ins ide of p ipes minimising the l ike l ihood of lead being present in dr ink ing water suppl ied through lead p ipes.

Plumbosolvency the tendency for lead to d issolve in water.

Polycyclic aromatic hydrocarbons

(PAHs)

is a group name for several substances present in petroleum-based products such as coal tar . (see Benzo(a)pyrene l is ted above for more informat ion) . A European health -based standard of 0.1μg/l for the sum of a l l the substances appl ies.

Powdered activated carbon (PAC)

powdered act ivated carbon is employed in treatment processes to remove pol lu tants.

Pre- and post-renovation assessment (PPRA)

a programme of assessment before and af ter mains renovat ion to demonstrate jus t i f icat ion for the work , and the improvements achieved by the renovat ion.

Prescribed concentration or value (PCV)

the numerical va lue assigned to dr ink ing water standards def in ing the maximal or min imal legal concentrat ion or value of a parameter .

Private supplies water suppl ied for human consumption or food product ion which is not provided by a water undertaker or l icensed water suppl ier .

Protozoan parasites a s ingle cel l organism that can only survive by infect ing a host.

Public Register dr ink ing water qual i t y informat ion made avai lable to the publ ic by water companies as required by regulat ions.

Public suppl ies water suppl ied by a company l icensed for that purpose.

Raw water water pr ior to receiv ing t reatment for the purpose of dr ink ing.

Regulations The W ater Supply (W ater Qual i t y) Regulat ions 2000 (England), 2010 (W ales).

Remedial act ion act ion taken to improve a s i tuat ion.

Residual disinfectant the small amount of ch lor ine or chloramines present in dr ink ing water to maintain i ts qual i t y as i t passes through the water company’s network of p ipes and household p lumbing.


60

Risk assessment

a review under taken to ident i f y ac tual or potent ia l hazards to human heal th in a water treatment works and assoc iated supply system. Pr ior i t isat ion of r isk is based on cons iderat ion of l ikel ihood and consequence of the r isk occurr ing.

Secretary of State Secretary of State for Environment, Food and Rural Af fairs .

Selenium is an essent ia l e lement and a necess ary d ietary component . Amounts in dr ink ing water are usual ly wel l below the standard. A European health-based s tandard of 10μg/ l appl ies.

Service connect ion connect ion between the water company's main to a consumer ’s property.

Service pipe any p ipe subject to mains water pressure or subject to mains pressure but for the c los ing of some valve.

Service reservoir a water tower, tank or other reservoir used for the s torage of treated water wi th in the d istr ibut ion system.

Sodium is a component of common sal t . I t is present in seawater and brack ish groundwater . Some treatment chemicals contain sodium. Concentrat ions in dr ink ing water are extremely low, but some water sof teners can add signif icant amounts to dr ink ing water where they are ins ta l led in homes or factor ies. A nat ional standard of 200mg/ l appl ies.

Springs groundwater appear ing at the surface at the outcrop of the junct ion of a permeable stratum with an impermeable s tratum.

Sulphate occurs natura l ly in a l l waters and is dif f icu lt to remove by treatment. An indicator parameter with a guide value of 250mg/ l .

Supply pipe see service p ipe.

Supply point a point other than a consumer ’s tap author ised for the tak ing of samples for compl iance wi th the regulat ions.

Surface water untreated water f rom r ivers, impounding reservoirs or other sur face water source.

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61

Taste can ar ise as a consequence of natura l processes in surface waters, par t icular ly between late spr ing and ear ly autumn. W ater treatment with act ivated carbon or ozone wi l l remove natura l substances caus ing taste. The s tandard relates to the evaluat ions of a panel of people assessing samples in the laboratory.

Technical audit the means of check ing that water companies are complying wi th their statutory obl igat ions.

Tetrachloroethane and Trichloroethene

are solvents that may occur in groundwater in the v ic in ity of industr ia l s i tes . W here necessary they are removed by spec ia l is t t reatment. A European health-based standard of 10μg/ l for the sum of both substances appl ies.

Tetrachloromethane is a solvent that may occur in groundwater in the v ic in i ty of industr ia l s i tes. Where necessary i t is removed by specia l is t water t reatment. A nat ional standard of 3μg/ l appl ies .

Time of supply the moment when water passes f rom the water company’s pipework in to a consumer’s p ipework.

Total indicat ive dose is a measure of the ef fect ive dose of radiat ion the body wi l l receive f rom consumpt ion of the water . I t is calculated only when screening values for gross a lpha or gross beta (rad iat ion) are exceeded. An indicator parameter wi th a guide value of 0.10mSv/year.

Total organic carbon represents the tota l amount of organic matter present in water . An indicator parameter wi th a guide value of ‘no abnormal change’.

Toxicology the s tudy of the health ef fects of substances.

Treated water water t reated for use for domestic purposes as def ined in the regulat ions.

Trihalomethanes are formed dur ing d is infect ion of water by a react ion between chlor ine and natural ly occurr ing organic substances. Their product ion is minimised by good operat ional pract ice. A European health-based standard of 100μg/l appl ies .

Trit ium is a radioact ive isotope of hydrogen. Discharges to the environment are str ic t ly control led and there is a nat ional programme of monitor ing surface waters. An indicator parameter wi th a guide value of 100Bq/ l .


62

Turbidity is a measure of the c loudiness of water. At treatment works, measurement is an important non-specif ic water qual i t y contro l parameter because i t can be monitored cont inuous ly on l ine and a larms set to a lert operators to deter iorat ion in raw water qual i t y or the need to opt imise water t reatment. An indicator parameter wi th a guide value of 1NTU. When detected at the consumer’s tap i t can ar ise f rom disturbance of sediment wi th in water mains. A nat ional s tandard of 4NTU appl ies in th is case.

Undertakings

legal ly b inding programmes of work agreed between a water company and the Chief Inspector of Dr ink ing Water to address actual or potent ia l water qual i t y issues.

Vinyl chloride may be present in p las t ic pipes as a res idual of the manufactur ing process of polyvinyl chlor ide (PVC) water p ipes. I ts presence in dr ink ing water is contro l led by product spec if icat ion. A European health-based standard of 0.5μg/ l appl ies .

Water supply zone a pre-def ined area of supply for establ ish ing sampl ing f requenc ies, compl iance wi th s tandards and informat ion to be made publ ic ly avai lable.

WHO World Health Organisat ion.

Wholesome/wholesomeness a legal concept of water qual i t y which is def ined by reference to s tandards and other requirements set out in the regulat ions.

Thames reg ion

63

Annex 3 Drinking water quality events in the region Not significant and minor drinking water quality events

Nature Number of not signif icant and minor events Area a ffected (est imate of populat ion affected)

Discolourat ion 1 – TMS (1 ) Gui ld ford , Sur rey (8,600 )

Loss of suppl ies /poor pressure 13 – TMS (10) , VCE (3) Reading, Berkshi re (4 ,000) Enf ie ld , London (22,700) Strat fo rd, London (135,460) South W est London (778,865) Woot ton Basset t , W i l tsh ire (15,350) Kingston-upon-Thames (4,425) South W est London (247,500) South W est London (237,125) Woodford Green, London (37,500) Chingford , Essex (32,900) Har low, Essex (7,500) Northwood and Ruis l ip , Middlesex (6,870) Woking, Surrey (132,853)

Microbio log ica l 3 – TMS (3 ) Edmonton, London (3) Tr ing, Hert fordshi re (17 ,000) Cockfosters , London (67 ,775)

Other 1 – TMS (1 ) Swindon, W i l tsh i re (3)


64

Nature Number of not signif icant and minor events Area a ffected (est imate of populat ion affected)

Publ ic concern 17 – SES (3) , TMS (12) , VCE (2) Oxted, Surrey (45) Carshal ton , Surrey (3) Edenbr idge, Kent (3) Reading, Berkshi re (3 ) Bow, East London (3) Hounslow, Middlesex (3) Mi tcham, Surrey (3) Cheshunt , Hert fo rdshi re (3) High W ycombe, Buck inghamshi re (4 ,225) Hendon, London (3) Camden, London (3) Wal tham Abbey, Essex (3) Hackney, London (3 ) Shalbourne, W i l tsh i re (3) Cr ick lade W i l tsh i re (15) St Albans, Hert fordshi re (5) Wembley, Middlesex (20)

Taste o r odour 2 – TMS (2 ) Bow, East London (3) Aston Ti r ro ld , Oxfordshi re (3)

Total 37 – SES (3) , TMS (29) , VCE (5) 1 ,760,781

Thames reg ion

65

Significant, serious and major drinking water quality events

Date and durat ion

Area Estimate of populat ion affected

Nature and cause of the event

Main act ions and f indings from the Inspectorate investigat ion

16 Jan 2010 For 1 day (TMS)

Farmoor works supplying areas of Banbury, Biceste r , Oxford and Swindon

517,000 Cryptospor id ium . Thames Water Uti l i t ies Ltd act ion:

Retra ined s ta f f .

Repai red fau l ty pre-ozonat ion equipment .

Subsequent f ina l water samples conta ined no Cryptospor id ium oocysts .

DWI comments and f indings:

The Inspectorate was sa t is f ied wi th the company’s handl ing of th is event and no recommendat ions were made.

Risk c lass i f icat ion: s ign i f icant

21 Jan 2010 For 2 days (TMS)

Wel l ing, Kent 8 ,775 Loss of suppl ies /poor pressure.

Thames Water Uti l i t ies Ltd act ion:

F lushed mains.

Repai red main.

Sampled af fected a rea. DWI comments and f indings:

Inadequate fo l low-up sampl ing.

Inadequate t ra in ing/competence of s ta f f . Risk c lass i f icat ion: s ign i f icant (see the Drink ing water qual i ty events sect ion)


66

Date and durat ion





Reading area 12,240 Brown d isco lourat ion .


F lushed mains.

Repai red main.


The Inspectorate was sa t is f ied with the company’s handl ing of th is event and no recommendat ions were made.


27 Jan 2010 For 2 days (VCE)

L i t t lebury Green, Saf f ron W alden

150 Musty taste o r odour.

Veolia Water Central act ion:

Retra ined s ta f f .

Sampled a f fected a rea.

F lushed mains. DWI comments and f indings:

In i t ia l f lush exacerbated the s i tuat ion

Inadequate t ra in ing/competence of s ta f f .

Incorrect va lve ar rangement for task .

Company unaware of p ipe mater ia l . Risk c lass i f icat ion: s ign i f icant


Twickenham. Middlesex

24,175 Discolourat ion . Thames Water Uti l i t ies Ltd act ion:

Sampled af fected a rea.

F lushed mains.

Updated geographica l in format ion systems (GIS) records


The Inspectorate was sa t is f ied wi t h the company’s handl ing of th is event and no recommendat ions were made.


Thames reg ion

67

Date and durat ion




09 Feb 2010 For 6 weeks (TMS)

Coppermi l ls works af fect ing nor th -east London

2,000,000 Taste and odour. Thames Water Uti l i t ies Ltd act ion:

Stopped abstract ion f rom contaminated source .

Af fected s torage reservo i rs removed f rom supply .

A l ternat i ve raw water used .

Ozone concentrat ion inc reased .

Ident i f ied chemical and source .

Review of r isk assessment .

Extens ive sampl ing o f raw water and t reated water .

Issued in format ion to consumers and media . DWI comments and f indings:

(see the Drink ing water qual i ty events sect ion)

Risk c lass i f icat ion: ser ious

26 Mar 2010 For 1 day (TMS)

North Orp ing ton works supplying areas of south east London

229,400 Microbio log ica l contaminat ion .



Invest igated works. DWI comments and f indings:

Inadequate t ra in ing /competence of s ta f f . Risk c lass i f icat ion: s ign i f icant

10 May 2010 For 4 hours (TMS)

Wal ton works supplying areas of south west London

39,165 Loss of d is in fect ion.


Repai red fau l ty equipment .

Shut down t reatment works.





68

Date and durat ion




21 May 2010 For 3 hours (SES)

Woodmansterne works supplying the areas of Burgh Heath and How Green, Sur rey

111,627 Compromised d is in fect ion .

Sutton And East Surrey Water Plc act ion:

Repai red fau l ty equipment .


Updated procedures. DWI comments and f indings:

Inadequate invest igat ions in to root cause.

Unacceptable de lay in not i fy ing Inspectorate. Risk c lass i f icat ion: s ign i f icant (see the Drink ing water qual i ty events sect ion)

17 Ju l 2010 For 1 day (TMS)

Goose Green Tower supplying the area of Hoddesdon, Lee Val ley

7 ,000 Microbio log ica l contaminat ion .


Bypassed service reservo i r .

Replaced fau l ty equipment . DWI comments and f indings:

Lack of maintenance of equipment .

Inadequate t ra in ing/competence of s ta f f . Risk c lass i f icat ion: s ign i f icant

11 Aug 2010 For 2 days (TMS)

Hornsey Lane reservo i r supplying areas of nor th London




Reservoi r inspect ion . DWI comments and f indings:

E.col i detected in a s tatutory sample f rom the reservo i r due to inadequate d is in fect ion of the sample point .


Thames reg ion

69

Date and durat ion




12 Aug 2010 For 12 hours (TMS)

Twickenham, Hounslow and Eal ing areas of west London

187,375 Loss of suppl ies /poor pressure .


Repai red burs t main.


Bot t led water suppl ied . DWI comments and f indings :



17 Sep 2010 For 2 days (TMS)

Farnborough Tower supplying the areas of Wantage and Oxford

113 Microbio log ica l contaminat ion .



Removed service reservo i r f rom supply.


Reservoi r inspected .

St ructura l fa i lure.

Ingress repai red . Risk c lass i f icat ion: s ign i f icant


70

Date and durat ion




29 Oct 2010 For 1 day (TMS)

Hornsey Lane works supplying areas of nor th London



Shut down t reatment works.

Des ludged the d isso lved a i r f loatat ion (DAF) p lant .

Conf i rmed tha t there was no issue wi th sampl ing fac i l i t ies .



The company was asked to conf i rm that a l l the mater ia ls o f construct ion and jo in t ing o f the sample l ine and tap comply wi th Regulat ion 31 of the W ater Supply (water qual i t y ) Regulat ions (2007) as amended. Inspectorate suggested the company conf i rms that the sampl ing arrangements a lso comply wi th i ts own asset s tandard.

Risk c lass i f icat ion : s ign i f icant

Thames reg ion

71

Event affecting a number of water companies

Date and durat ion

Nature and cause of event

Main act ions and f indings from the Inspectorate invest igat ion

02 Ju l 2010 Durat ion no t appl icable (Severn Trent Services)

Analyt ica l malpract ice .

DWI comments and f indings :

Ser ious def ic ienc ies were found b y the water undertakers or the combined l icensees for fa i l ing to meet the i r ob l igat ions under Regulat ions 16 and 34 for analys is o f water samples and, in par t icu lar , der i ved analyt ica l d a ta, competency, re tent ion of appropr ia te records , and fo r the appropr ia te t ime , us ing su i tab le equipment found in analyt ica l pract ices for inorganic chemical analys is (Regulat ion 16) .

Fu l l deta i ls in the publ ished audi t report .

In i t ia ted enfo rcement ac t ion in re la t ion to the e ight water companies us ing Severn Trent Services .

Risk c lass i f icat ion: ser ious

Note: A complete table of events in England and W ales in 2010 can be found on the CD in the fo lder. I t is named Signif icant drinking water events in England and Wales 2010.pdf . I t is also avai lable on the DW I webs i te (www.dwi.gov.uk).


72

Annex 4 Planned drinking water quality improvements

Company Parameter, hazard or dr iver

Site Due for complet ion

Status Legal Instrument

SES Lead Dis t r ibut ion s ystem 31-Mar-15 Ongoing Undertak ing

SES Meta ldehyde Bough Beech 31-Mar-15 Ongoing Undertak ing

SSE Meta ldehyde

Bulk supply f rom Thames W ater in to Bromley Common

31-Mar-15 Ongoing Undertak ing

SSE Meta ldehyde

Bulk supply f rom Thames W ater in to Hale Vi l lage , Tot tenham


SSE Meta ldehyde Bulk supply f rom Thames W ater in to Kennet Is land


TMS Atrazine, Monuron and Pic loram

Woods Farm 30-Sep-13 Ongoing Undertak ing

TMS Chlor to luron Harpsden catchment


TMS Cryptospor id ium Fair ford 31-Mar-12 Ongoing Not ice

TMS Cryptospor id ium Marlborough 31-Mar-12 Ongoing Not ice

TMS Cryptospor id ium Playhatch 30-Jun-12 Ongoing Not ice

TMS Inadequate d is in fect ion

Br i xton 31-Dec-10 Completed 31-Dec-10

Not ice


Farmoor 30-Sep-12 Ongoing Not ice


Honor Oak 31-Mar-12 Ongoing Not ice


Radnage 31-Mar-12 Ongoing Not ice

TMS Ingress Dancers End 31-Mar-12 Ongoing Not ice

TMS Ingress Kidderpore 31-Mar-12 Ongoing Not ice

TMS I ron and Turb id i ty

Has lemere 31-Mar-10 Completed 08-Feb-10

Not ice

TMS I ron Chipping Norton 31-Dec-11 Ongoing Undertak ing

TMS Lead Dis t r ibut ion system 31-Mar-15 Ongoing Undertak ing

TMS Lead Aylesbury East 31-Dec-11 Ongoing Undertak ing

TMS Lead Henley 31-Dec-11 Ongoing Undertak ing

TMS Meta ldehyde Coppermi l ls and Chingford South catchments


TMS Meta ldehyde Farmoor and Swinford


TMS Meta ldehyde Fobney catchment 31-Mar-15 Ongoing Undertak ing

TMS Meta ldehyde Gr imsbury catchment


TMS Meta ldehyde Hornsey catchment 31-Mar-15 Ongoing Undertak ing

Thames reg ion

73

Company Parameter, hazard or dr iver

Site Due for complet ion

Status Legal Instrument

TMS Meta ldehyde Shal ford catchment


TMS Meta ldehyde

Bulk supply f rom Angl ian W ater in to F inmere Goding ton and Long Marston


TMS Meta ldehyde West London catchments


TMS Ni t ra te Manor Road Wantage

30-Sep-12 Ongoing Undertak ing

TMS Ni t ra te Westerham 31-Mar-12 Ongoing Undertak ing

TMS Pest ic ides Sheafhouse catchment


TMS Power supply Ashford Common 31-Mar-13 Ongoing Not ice

TMS Power supply Coppermi l ls 31-Mar-15 Ongoing Not ice

TMS Power supply Hampton 31-Mar-13 Ongoing Not ice

VCE Bromate North Mymms 31-Mar-10 Completed 30-Mar-10

Undertak ing

VCE Cryptospor id ium Chor leywood 31-Mar-11 Completed 21-Mar-11

Undertak ing

VCE Manganese Blackford 31-Mar-15 Ongoing Undertak ing

VCE Manganese Roydon 30-Apr-14 Ongoing Undertak ing

VCE Meta ldehyde Chertsey catchment


VCE Meta ldehyde Egham catchment 31-Mar-15 Ongoing Undertak ing

VCE Meta ldehyde Iver catchment 31-Mar-15 Ongoing Undertak ing

VCE Meta ldehyde North Mymms catchment


VCE Meta ldehyde Wal ton catchment 31-Mar-15 Ongoing Undertak ing

VCE Meta ldehyde

Bulk supply f rom Essex and Suf fo lk Water in to Pi lgr ims Hatch


VCE Meta ldehyde

Bulk supply f rom Angl ian W ater in to Knebwor th /Tewin, Hat f ie ld /Pot ters Bar and Luton North


VCE Ni t ra te Kings W alden 31-Mar-14 Ongoing Undertak ing


74

Annex 5

Competition in the water industry The following table indicates the extent of competit ion in the water industry in England and Wales . Inset appointments in place in 2010 Site Appointee Incumbent and

region Status

Shotton Paper , Shotton

Alb ion W ater Dŵr Cymru, Wales

Supplying water

Buxted Chicken, Fl ix ton

Angl ian W ater Essex and Suf fo lk Water, Eastern region

Supplying water

W ynyard, near Wolviston

Har t lepool Water Nor thumbr ian W ater, Nor thern region

Supplying water

Brook lands, Mi l ton Keynes

Independent Water Networks Ltd

Angl ian W ater, Eastern region

Supplying water

Great Bi l l ing Way, Nor thampton



Supplying water

Long Crof t Road, Corby



Supplying water

Pr iors Hal l , Corby Independent Water Networks Ltd


Supplying water

Kings Cross, London Independent Water Networks Ltd

Thames Water, Thames region

Supplying water

The Br idge, Dar tford Independent Water Networks Ltd


Supplying water

Media City, Salford Quays

Peel Water Networks Ltd

Uni ted Ut i l i t ies, Nor thern region

Supplying water

Grayl ingwel l , Chichester

SSE W ater Portsmouth Water/Southern W ater, Southern region

Supplying water

Bromley Common, Bromley

SSE W ater Thames Water, Thames region

Supplying water

Hale Vi l lage, Tottenham


Supplying water

Kennet Is land, Reading


Supplying water

Park Views, Epsom SSE W ater Thames Water, Thames region

Supplying water

The Portway, near Sal isbury

SSE W ater Wessex W ater, Western region

Supplying water

Fair f ie ld Park and Lower W ilbury Farm, Ar lesey



Supplying water

MoD T idworth near Andover

Veol ia W ater Projects

Wessex W ater, Western region

Supplying water

Thames reg ion

75

New inset appointments in place for 2010 (by 31 May 2011)

Site Appointee Incumbent and region

Status

Berryf ie lds , Aylesbury



Supplying water f rom Apr i l 2011

L lani l id Park , South W ales

SSE W ater Dŵr Cymru, Wales

Appointment granted

Great Western Park , Didcot


Supplying water f rom Apr i l 2011

Kingsmere, Bicester


Appointment granted

Water supply licenses in place in 2010

Name of company License type

Date l icense granted by Ofwat

Status

Aquavitae Combined 1 December 05 L icence revoked

Avon Val ley W ater Reta i l 6 August 10 Not yet operat ing

Business Stream Retai l 23 January 09 Not yet operat ing

Osprey W ater Services Ltd

Combined 5 January 07 Not yet operat ing

Satec Ltd Combined 24 May 06 Not yet operat ing

Severn Trent W ater Select Ltd

Combined 1 December 05 One reta i l customer Eastern region

UU Water Sales Ltd Combined 3 January 07 Not yet operat ing

Watercal l L td

Combined 1 December 05 Inact ive

YorWater Ltd Retai l 21 March 06 Not yet operat ing


76

Annex 6 Water company indices



Company assets Water supplied

Number of treatment works 0 Water suppl ied (Ml/day)

0.34

Number of service reservoirs 0 Percentage f rom surface sources

>99%

Number of water supply zones 6 Percentage f rom ground sources

<1%

Length of mains p ipe (km) 15 Percentage f rom mixed sources

0

Population served Area of supply

Priors Hal l and Long Croft Road, Corby, Great Bi l l ing Way, Northampton, Brooklands, Milton Keynes, Kings Cross, London, The Bridge, Dartford

Populat ion supplied 2,000

Number of local author it ies 1

Drinking water quality summary data

Company f igure Industry average

2008 2009 2010 2010

Overal l drinking water quality* 100% 99.94% 99.93% 99.96%

Water t reatment

Process Contro l Index N/A N/A N/A 99.99%

Dis infect ion Index N/A N/A N/A 99.97%

Distribution systems

Dis tr ibut ion Maintenance Index 100% 100% 100% 99.86%

Reservoir In tegr i ty Index N/A N/A N/A 99.96%

Building water systems

Parameters inf luenced by domest ic water systems

100% 99.69% 99.85% 99.89%

Consumer contacts


2008 2009 2010 2010

Informing consumers

Tota l number 0 0 1 N/A

Rate per 1 ,000 populat ion 0 0 0.41 1.26

Acceptabi l ity of water to consumers



Complaints to the Drinking Water Inspectorate

No consumers of Independent W ater Networks Ltd direc t ly contacted DW I in 2010.

Note: Summary resu l t s for each company o f tes ts for i nd i v idua l parameters are supp l ied on the DW I webs i te a t www.dwi .gov.uk

* Overa l l d r ink ing water qua l i t y as rep resented by mean zona l compl iance fo r 39 parameters .


Thames reg ion

77

Sutton and East Surrey Water plc




159


15


85

Length of mains p ipe (km) 3,436 Percentage f rom mixed sources

0


Parts of Surrey, Sussex, Kent, LB Sutton, LB Croydon, LB Merton





2008 2009 2010 2010

Overal l drinking water quality* 99.89% 99.92% 99.99% 99.96%

Water t reatment

Process Contro l Index 100% 100% 100% 99.99%

Dis infect ion Index 99.98% 100% 99.99% 99.97%


Dis tr ibut ion Maintenance Index 99.86% 99.84% 99.94% 99.86%

Reservoir In tegr i ty Index 100% 100% 100% 99.96%



99.96% 99.92% 99.99% 99.89%

Consumer contacts


2008 2009 2010 2010

Informing consumers


Rate per 1 ,000 populat ion 0.15 0.22 0.24 1.26





No consumers of Sutton and East Surrey W ater p lc d irect ly contacted DW I in 2010.

Note: Summary resu l t s for each company o f tes ts for i nd i v id ua l parameters are supp l ied on the DW I webs i te a t www.dwi .gov.uk




78

SSE Water




0.26


50


47

Length of mains p ipe (km) 9 Percentage f rom mixed sources

3


Old Sarum, near Sal isbury;

Hale Vi l lage, Tottenham; Grayl ingwell , Chichester; Bromley Common, Bromley; Kennet Island, Reading; Park Views, Epsom





2008 2009 2010 2010

Overal l drinking water quality* 100% 100% 100% 99.96%

Water t reatment

Process Contro l Index N/A N/A N/A 99.99%

Dis infect ion Index N/A N/A N/A 99.97%


Dis tr ibut ion Maintenance Index 100% 100% 100% 99.86%

Reservoir In tegr i ty Index N/A N/A N/A 99.96%



100% 100% 100% 99.89%

Consumer contacts


2008 2009 2010 2010

Informing consumers Total number 0 1 1 N/A

Rate per 1 ,000 populat ion 0 0.74 0.5 1.26




Complaints to the Drinking Wat er Inspectorate

No consumers of SSE Water d irect ly contacted DW I in 2010.

Note : Summary resu l t s for each company o f tes ts for i nd i v idua l parameters are supp l ied on the DW I webs i te a t www.dwi .gov.uk



Thames reg ion

79

Thames Water Utilities Ltd




2,793


76


24


0


Bedfordshire (part) , Berkshire (part) , Buckinghamshire (part) , Essex (part) , Gloucestershire (part ) , Hampshire (part) , Hertfordshire, Kent (part) , Inner London, Outer London (part) ,Oxfordshire, Surrey (part ) , West Sussex (part) , Warwickshire (part) , Wiltshire (part )

Populat ion supplied 8,630,000




2008 2009 2010 2010


Water t reatment

Process Contro l Index >99.99% >99.99% 99.99% 99.99%

Dis infect ion Index 99.97% 99.95% 99.96% 99.97%



Reservoir In tegr i ty Index 99.97% 99.94% 99.94% 99.96%



99.93% 99.91% 99.89% 99.89%

Consumer contacts


2008 2009 2010 2010

Informing consumers

Tota l number 40,877 49,541 41,499 N/A



Tota l number 8,753 7,251 6,324 N/A



A tota l of 23 consumers of Thames Water Ut i l i t ies Ltd d irect ly contacted DWI in 2010.

Note: Summary resu l t s for each comp any o f tes ts for i nd i v idua l parameters are supp l ied on the DW I webs i te a t www.dwi .gov.uk * Overa l l d r ink ing water qua l i t y as rep resented by mean zona l compl iance fo r 39 parameters .



80

Veolia Water Central




872


40


55


5


Hertfordshire, Bedfordshire, Essex, Buckinghamshire, Berkshire, Surrey and 9 London Boroughs

Populat ion supplied 3,043,000




2008 2009 2010 2010


Water t reatment

Process Contro l Index 99.99% 99.99% 100% 99.99%

Dis infect ion Index 99.95% 99.96% >99.99% 99.97%



Reservoir In tegr i ty Index 99.95% 99.98% 99.99% 99.96%



99.94% 99.85% 99.95% 99.89%

Consumer contacts


2008 2009 2010 2010

Informing consumers

Tota l number 1,818 1,585 1,697 N/A



Tota l number 6,590 4,305 4,041 N/A



A tota l of 2 consumers of Veol ia W ater Centra l d irec t ly contacted DWI in 2010.

Note : Summary resu l t s for each company o f tes ts for i nd i v idua l parameters are supp l ied on the DW I webs i te a t www.dwi .gov.uk



Drinking Water Inspectorate | 55, Whitehall | London | SW1A 2EY | Tel: 020 7270 3370

http://www.dwi.gov.uk

Drinking Water Inspectorate | Ergon House, Horseferry Road | London | SW1P 2AL | Tel: 030 0068 6400

www.dwi.gov.uk

PB13480

Drinking water2010Public water supplies in the Thames region of EnglandJuly 2011A report by the Chief Inspector of Drinking Water

Drinking w

ater 2010 P

ublic water supplies in the Tham

es region of England

Documents

Drinking water 2010 - DWI, UKdwi.defra.gov.uk/about/annual-report/2010/thames.pdf · Drinking water 2010 4 Introduction to the report for the Thames region Drinking water 2010 is