Cryptosporidium and Water Supplies in England and Wales

1
Cryptosporidium and Water Supplies in England and
Wales

• Professor Jeni Colbourne
• Chief Inspector of Drinking Water

2
Cryptosporidium in Water SuppliesThe England and
Wales story

• 1990 Reform of water law/industry coincident with
  large surface water outbreak of cryptosporidiosis
• Independent Expert Group recommendations
  (Badenoch)
• 1997 Large ground water outbreak of
  cryptosporidiosis
• Independent Expert Group recommendations
  (Bouchier)
• 1999 New regulations for risk assessment/monitorin
  g led to significant investment in targetted
  additional treatment and reduced occurrence of
  oocysts in water
• 2005 two large outbreaks one well controlled
  (additional treatment under construction) the
  other resulted in prosecution of the water
  company (risk wrongly assessed and treatment
  inadequate)
• 2007 Regulations amended (water safety plans
  underpinned by raw water monitoring, stiff
  penalties for failure to treat and disinfect)

3
The water industry in England and WalesFacts and
figures (in 2007)

• Industry
• privatised water companies
• 53.3 million consumers
• 99 population
• 16,000 m3/d water supplied
• Infrastructure
• 1300 water treatment works
• 4600 service reservoirs
• 332,000 km mains
• Drinking Water Quality
• gt99.9 tests met European and National standards
  in 2006 (compared to 95 in 1991)

4
Drinking Water Inspectorate

• Set up in 1990
• Independent drinking water quality regulator
• To ensure water companies produce wholesome water
  that is fit for human consumption
• Main powers
• Obtain monitoring and other information
• Technical audit, entry and inspection
• Enforcement and Prosecution
• Independent publication of results/advice

5
Expert Group on Cryptosporidium in Water Supplies

• Set up by government in March 1989
• Response to public concern over a large
  waterborne outbreak of cryptosporidiosis in
  Oxford/Swindon (surface water)
• Richardson, Frankberg, Buck, Selkon, Colbourne,
  Parsons, Mayon-White 1991 Journal of Epidemiology
  and Infection Vol 107, 485-495
• Chaired by the late Sir John Badenoch

6
First Expert Group Report July 1990

• First comprehensive review of Cryptosporidium and
  water supplies
• Independent appraisal of evidence
• Assessed scientific and technical data
• Initiated collaborative research programme
• Made 53 recommendations
• Majority still valid today

7
Second Expert Group Report October 1995

• Review of research findings
• Improved knowledge about
• Occurrence
• Control
• Testing
• Few additional recommendations
• Expert Group wound up but research programme
  continued

8
Badenoch recommendations

• 53 recommendations covering
• Recovery, identification and typing of the
  organism (testing)
• Control of Cryptosporidium in the environment
  (risk identification)
• Controlling the spread of infection in man
  (health surveillance)
• Water treatment and distribution
• Role of monitoring for oocysts in water
• Investigation and management of outbreaks

9
Key recommendations on water treatment

• Design and operation of treatment plant to be
  optimised for particle removal (turbidity meters
  at all stages of filtration)
• Rapid changes of flow through treatment to be
  minimised (soft start of filters, no bypassing)
• Design of systems for separating supernatant
  water from sludge and backwash water (no
  recycling without specific precautions)
• Monitoring of raw water related to an assessment
  of catchment risks and the level/type of
  treatment (site specific)
• Codes of agricultural good practice to be
  promoted and reviewed regularly
• Filtration without coagulation recognised as
  inadequate for removal of chlorine resistant
  pathogens

10
Key recommendations on investigation and
management of an outbreak

• Formalise regular liaison between the relevant
  staff of water utilities, health authorities and
  local authorities this should not be confined
  to just times when there are problems
• Health authorities, local authorities and water
  utilities to update and rehearse existing
  emergency and outbreak control plans
• Incident team must agree procedures for the
  issuing and withdrawal of boil water advice.
  When considering imposing such advice there must
  be clear criteria for its withdrawal
• Incident team must have an effective
  communication plan for the public and media.
  This should be part of plans and rehearsed
  regularly
• Methodology for epidemiological surveillance and
  outbreak case control studies

11
Third Expert Group Report

• Expert Group re-convened in 1997
• In response to a large outbreak of waterborne
  cryptosporidiosis in north west London
• First major groundwater-associated outbreak
• Chaired by Professor Ian Bouchier
• Reported November 1998

12
Third Expert Group Report

• Outbreaks do not just happen
• Strong correlation between outbreaks and
  situations where treatment provision was
  inadequate or operation of treatment process was
  compromised
• Groundwater quality can be affected by rapid
  transmission of water from the surface
  intermittently and such sources are potentially
  at high risk of contamination by Cryptosporidium

13
Third report main cause of outbreaks of
waterborne cryptosporidiosis

• Agricultural slurry contamination of water in
  distribution
• Contamination of source water with animal wastes,
  insufficient treatment
• River flows abnormally low, severe diarrhoea in
  cattle upstream of intake
• Unfiltered water or filters bypassed
• Rapid fluctuations in raw water quality
• Heavy rainfall in catchment, high turbidity in
  raw water
• Faecal contamination from cattle housed close to
  wellhead
• Rapid recharge of groundwater with contaminated
  surface water
• Heavy rainfall, run-off from grazing land
• Poor operating practice, excessive head on
  filters
• Plant operating above design output
• Plant unable to cope with a raw water algal bloom
  

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Third Report Recommendations

• Water utilities should ensure that employees
  operating assets producing drinking water are
  aware of the circumstances which can potentially
  put water supplies at risk of Cryptosporidium
  contamination
• Procedures should be in place to ensure rapid
  recognition and appraisal of risks associated
  with any relevant change in operational
  circumstances

15
Third Report Recommendations

• Water utilities should carry out an assessment of
  risk from Cryptosporidium for each source and put
  in place a procedure for periodically updating
  risk assessment
• Water treatment works should be designed
  according to risk assessment and be able to
  handle the typical peak turbidity and colour
  loadings in the source water
• Water treatment works should be operated at all
  times in a manner that minimises turbidity in the
  final water
• Filters should be operated and maintained under
  optimum conditions with attention to the quality
  and depth of media and to the operation of
  backwashing

16

Impact of regulating for Cryptosporidium risk
assessment and management in 1999

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Risk assessment findings

• 1481 water treatment works in England and Wales
• 332 identified as at significant risk
• 158 works treating surface water
• 174 works treating groundwater

18
Impact of Cryptosporidium Regulations

• 103 small works abandoned
• 51 works with membranes installed
• 179 works where treatment process improvements
  were made e.g. coagulation, filtration, turbidity
  management

Risks understood Treatment barriers more robust
19
Cryptosporidium validation monitoringof at
risk water suppliesPercentage of samples with
Cryptosporidium detected
20
So what happened in November 2005

• 2 outbreaks of C.hominis (human strain)
• 1 in England 1 in Wales
• Root cause sewage contamination of raw water
  (human infection is higher in late summer/autumn
  possibly due to overseas travel)

21
Itchen outbreak in England

• Urban surface water source with major sewage
  discharge 3km upstream
• Coagulation/filtration/chlorination in place
• Classified at significant risk (membrane plant
  under construction due to come on line in June
  2006)
• Risk management plan in place and agreed with
  health and local authorities
• Raw water monitoring notification trigger values
• Weekly health surveillance identified a slight
  rise in cases above normal which was notified to
  water company
• Arrangements in place to switch to alternative
  supplies (rezoning)
• Treatment reviewed, further optimised and works
  brought back on line
• Outbreak controlled (cases returned to background
  level)
• Additional membrane treatment commissioned 6
  months later
• Epidemiological case control study weak and
  inconclusive

22
Cwellyn outbreak in Wales

• Upland lake source receives discharges from small
  sewage works and septic tanks (sheep grazing)
• Pressure filters for Mn removal/chlorination only
• Classified as NOT at risk (lake assumed to be an
  effective barrier)
• No risk management plan in place with health and
  local authorities
• abnormally high number of cases diagnosed by
  local hospital
• Initial boil water health advice given was for
  immuno-compromised people only
• 2 weeks later boil water advice issued to whole
  population
• Boil water advice lasted for 3 months until water
  company had installed and commissioned additional
  treatment (UV)
• Testing (after cases reported) showed low numbers
  of oocysts present in both raw and treated water

23
Cwellyn outbreak in Wales

• 1995 A1 SWAD pristine classification of lake by
  EA unjustified (faecal organisms present)
• 1999 cryptosporidium risk assessment based on
  incomplete information (septic tanks not
  documented, raw water monitoring infrequent and
  not reviewed, hydraulic conditions in lake
  assumed not measured)
• Treatment design/operation did not meet
  Badenoch/Bouchier recommendations (pressure
  filters without coagulation, flow meters and
  turbidity meters not calibrated) over reliance
  on and misunderstanding of treatment standard in
  crypto regulations.
• No procedures for review of raw water data
• No outbreak control/emergency plan in place
• Dwyr Cymru Welsh Water successfully prosecuted by
  DWI for supplying water unfit for human
  consumption
• Company has since installed raw water monitoring
  at 46 other works and identified 18 where
  additional treatment is required (mostly
  coagulation).
• Epidemiological case control study showed very
  strong association between illness and consuming
  unboiled tap water

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Amendment Regulations 2007

• Companies required to monitor raw water and
  report results to DWI
• Companies required to carry out comprehensive
  risk assessment (using WHO water safety plan
  methodology covering all hazards)
• Risk assessment to inform the implementation of
  short, medium and long term controls
• Requirement for adequate treatment and
  disinfection (replaces SWAD treatment criteria of
  A1, A2, A3)
• Failure to treat/disinfect is a criminal offence
• Proposals for additional treatment investment
  through Water Price Review (Ofwat) will be
  directly linked to outputs of water safety plans
  (risk based)
• 1999 cryptosporidium regulations revoked

25
Bouchier Report (contains Badenoch
recommendations is available on the DWI website
www.dwi.gov.uk
www.dwi.gov.uk/pubs/bouchier/index.htm