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Liz Stokle Senior Health Protection Nurse North East Health Protection Unit Guidance for Responding to Drinking Water Quality Failures in the North East.

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Presentation on theme: "Liz Stokle Senior Health Protection Nurse North East Health Protection Unit Guidance for Responding to Drinking Water Quality Failures in the North East."— Presentation transcript:

1 Liz Stokle Senior Health Protection Nurse North East Health Protection Unit Guidance for Responding to Drinking Water Quality Failures in the North East of England, March 2012

2 Responsibilities of Health Protection Unit Health Protection Agency Act 2004 HPA has a duty to protect the public from threats …infectious diseases and environmental hazards. Following Notification the HPU with the local authority is to provide public health advice to the water company …pertinent to the local community affected. Significant threat to public health, the HPU has a duty to inform the appropriate Director of Public Health for the (PCT) responsible for the health of the population affected and then to work on mitigation.

3 Challenges for risk assessment Raw water abstraction Treated water Nature of problem failure – problems at WTW; burst main; discoloured water; loss of supply; failure of standard at any point in process

4 Challenges for risk assessment Raw water abstraction Treated water Nature of problem/failure Chemical and microbiological parameters

5 Microbiological parameters Indicator Organisms Coliforms Faecal indicators: E.Coli Enterococci C.Perfringens

6 Multiple variables Coliforms Alone or in conjunction with other organisms such as E.coli Small numbers or high numbers

7 Other biological & chemical parameters Cryptosporidium Lead Fluoride Chlorine or lack of

8 Drinking water safety “The significance of individual test results for each microbiological parameter at each location varies and a single positive result does not necessarily mean that water is unsafe [or safe] to drink. Other information is required to assess water safety.” Drinking Water Safety -Guidance to health and water Professionals (DWI/HPA December 2009)

9 Risk Assessment Severity of consequences of the hazard: Effect on human health not just Meeting health based standards and indicator parameter values The risk associated with the hazard needs to be considered in the context of the particular situation/circumstances

10 Contextual issues Point of failure Nature of failure Size of population affected Nature of population affected Current awareness of GI illness

11 Challenges for protecting health of population Interpreting the information/evidence Risk assessment appropriate to context Implementing proportionate response

12 Launch of document

13 Failure of Prescribed Concentration or Value (PCV) LA first response (response should be initiated at presumptive stage within 1 working day of receipt of event notification) HPA first response (response should be initiated at presumptive stage within 1 working day of receipt of event notification) Standard response (within 1 month) 1. Coliforms 1-50 per 100ml in the ABSENCE of E. coli (otherwise action as for E.coli) Discuss circumstances and context of failure with NWL/HW e.g. burst main, contamination at service reservoir:  Assess: chlorine levels, cause of failure, population at risk & any currently known increase in gastrointestinal illness  Consider whether site visit to implicated location is necessary (may involve liaison with other LAs & water company for access if wide distribution area affected)  Agree NWL/HW actions Discuss circumstances and context of failure with NWL/HW e.g. burst main, contamination at service reservoir:  Assess: chlorine levels, cause of failure, population at risk & any currently known increase in gastrointestinal illness via current HPU surveillance systems  Agree NWL/HW actions  NWL/HW to report outcome of any follow-up samples as soon as available 1a. Coliforms >50 per 100ml in the ABSENCE of E. coli (otherwise action as for E.coli) Value >50 coliforms with or without E.coli is an indication of poor quality drinking water As above PLUS  Any abnormal changes in colony counts  Agree measures to investigate ‘integrity of the system’  Agree with Water supplier further investigations for faecal contamination Value >50 coliforms with or without E.coli is an indication of poor quality drinking water As above PLUS  Any abnormal changes in colony counts  Agree measures to investigate ‘integrity of the system’  Agree with Water supplier further investigations for faecal contamination  NWL/HW to report outcome of any follow-up samples as soon as available 2. E.coli 1–10 per 100ml (without coliforms or with coliforms up to a level of 50) As above PLUS consider if ‘boil water’ advice should be issued  If ‘boil water’ advice agreed, also agree conditions required to remove the boil water notice As above PLUS consider if ‘boil water’ advice should be issued and document rationale  If ‘boil water’ advice agreed, also agree conditions required to remove the boil water advice As above PLUS  NWL/HW remove ‘boil water’ advice when agreed conditions achieved 3. E. coli >10 per 100ml (especially where coliforms >50) As above PLUS consider immediate check sampling from consumers taps in affected area to verify NWL/HW bacterial sample results As above PLUS discuss context & boil water advice 4. Cryptosporidium oocysts (any number) and/or report of turbidity >1 NTU at water treatment works or >4 NTUs at customer tap (Continued over) Discuss context of failure in relation to extra evidence of risk i.e. aware of:  Cluster/increase in cases in affected area  Ingress at treatment works or in distribution network  Treatment failure or turbidity failure in treated water Where no extra evidence of risk (as described above) and failure level low i.e. <1 oocyst/10 litres  Agree action for resampling and investigation of cause Where extra evidence of risk exists (as described above) and/or failure significant numbers i.e. >1 oocyst/10 litres in treated water  Consider boil water advice with NWL/HW  Agree conditions required to remove the boil water notice  Alert EHO colleagues to be vigilant for cases Discuss context of failure in relation to extra evidence i.e. aware of:  Cluster/increase in cases in affected area  Ingress at treatment works or in distribution network  Treatment failure or turbidity failure in treated water Where no extra evidence of risk (as described above) and failure level low i.e. <1 oocyst/10 litres  Agree action for resampling and investigation of cause Where extra evidence of risk exists (as described above) and/or failure significant numbers i.e. >1 oocyst/10 litres in treated water. Discuss with senior to:  Consider boil water advice with NWL/HW  Agree conditions required to remove the boil water advice  Alert HPU staff to enhanced surveillance for cases As above PLUS  NWL/HW Remove ‘boil water’ advice when agreed conditions achieved  HPU enhanced surveillance for increase in community cases  NWL/HW to report outcome of investigation Table 1: Response to notification from Northumbrian Water Limited or Hartlepool Water relating to failures of mains water samples or of events posing a threat to supply [

14 Reported failure – Mains Water Domestic property – programmed sample result: 42 presumptive coliforms 0 E.coli Free chlorine 0.16 mg/l Total Chlorine 0.25 mg/l

15 Failure of Prescribe d Concentra tion or Value (PCV) LA first response (response should be initiated at presumptive stage within 1 working day of receipt of event notification) HPA first response (response should be initiated at presumptive stage within 1 working day of receipt of event notification) Standard response (within 1 month) 1. Coliforms 1-50 per 100ml in the ABSENCE of E. coli (otherwis e action as for E.coli) Discuss circumstances and context of failure with NWL/HW e.g. burst main, contamination at service reservoir:  Assess: chlorine levels, cause of failure, population at risk & any currently known increase in gastrointestinal illness  Consider whether site visit to implicated location is necessary (may involve liaison with other LAs & water company for access if wide distribution area affected)  Agree NWL/HW actions Discuss circumstances and context of failure with NWL/HW e.g. burst main, contamination at service reservoir:  Assess: chlorine levels, cause of failure, population at risk & any currently known increase in gastrointestinal illness via current HPU surveillance systems  Agree NWL/HW actions  NWL/HW to report outcome of any follow-up samples as soon as available

16 Table 2 : Response to failures of private water samples Type of Failure - of Prescribed Concentration or Value (PCV) Local AuthorityHPA first response (on receipt of notification from LA unless otherwise stated) Long term response LA and/or HPU as indicated (> 1 month and up to the 5 year review of the supply risk assessment) First response (within 3 working days of receipt of result unless otherwise stated) Standard response (within 1 month of last result) Consider serving notice under regulation Coliforms 1-5 per100ml in the ASBSENCE of E. coli (if E. coli present action as for E. coli below)  Inform owner/person responsible for supply & advise on improvements & checks to system  Undertake an investigation and/or risk assessment  Provide further advice on any improvements required based on risk assessment HPU not informedLA revise supply risk assessment 2. Coliforms - any number >5 per 100ml in the ASBSENCE of E. coli (if E. coli present action as for E.coli below)  Inform owner/person responsible for supply & advise on improvements & checks to system  Undertake an investigation and/or risk assessment  Provide further advice on any improvements required based on risk assessment  Where number of coliforms >50/100ml persists after re- sampling inform HPU  Consider Boil Water Notice* Where number of coliforms >50/100ml persists in resamples after improvements have been made, clarify with LA:  Number of properties on supply  Whether a ‘high risk’ supply e.g. includes commercial food or public premises  Whether a private distribution system  Consider Boil Water Notice*  LA and HPU agree remedial action and follow-up  If Boil Water Notice in place agree criteria for lifting notice  HPU consider/continue enhanced surveillance for GI illness using routine surveillance or contacting local GPs according to size of failure If re-samples pass LA revise supply risk assessment as appropriate 3. E. coli 1-5 per 100ml  Inform owner/person responsible for supply & advise on improvements & checks to system  Issue a Boil Water Notice  Issue health advice to all consumers  Undertake RA/investigation including sampling  Where E.coli persists in samples after improvements have been made:Discuss with HPU  Inform owner/person responsible for supply & advise on improvements & checks to system  Agree supply improvement actions with owner/person responsible for the supply  Where E.coli persists in samples after improvements have been made, as actions in 2 above PLUS Discuss cause of failure  Size and nature of population at risk  Any currently known increase in GI illness Agree remedial action with LADiscuss boil water advice with LA and agree criteria for lifting the advice based on results & evidence that risks identified in risk assessment have been controlled as 2 above PLUS  HPU consider/continue enhanced surveillance for GI illness If re-samples pass as 2 above PLUS  LA revise supply risk assessment on completion of any improvement works

17 Reported failure – Private Water Domestic property – programmed sample result: 42 presumptive coliforms 0 E.coli Free chlorine ? Total Chlorine ?

18 Private Water Supply 2. Coliforms - any number >5 per 100ml in the ABSENCE of E. coli (if E. coli present action as for E.coli below)  Inform owner/person responsible for supply & advise on improvements & checks to system  Undertake an investigation and/or risk assessment  Provide further advice on any improvements required based on risk assessment  Where number of coliforms >50/100ml persists after re- sampling inform HPU  Consider Boil Water Notice* Where number of coliforms >50/100ml persists in resamples after improvements have been made, clarify with LA:  Number of properties on supply  Whether a ‘high risk’ supply e.g. includes commercial food or public premises  Whether a private distribution system  Consider Boil Water Notice*  LA and HPU agree remedial action and follow-up  If Boil Water Notice in place agree criteria for lifting notice  HPU consider/continue enhanced surveillance for GI illness using routine surveillance or contacting local GPs according to size of failure If re-samples pass LA revise supply risk assessment as appropriate

19 Coliforms in PWS * Where failure relates to coliforms without evidence of E.coli consider history of supply (where available) in relation to evidence that this result may suggest potential danger to human health e.g. management of supply not effective – in such cases a boil water notice may be warranted

20 Private Water Supplies 3. E. coli 1-5 per 100ml  Inform owner/person responsible for supply & advise on improvements & checks to system  Issue a Boil Water Notice  Issue health advice to all consumers  Undertake RA/investigation including sampling  Where E.coli persists in samples after improvements have been made:Discuss with HPU  Inform owner/person responsible for supply & advise on improvements & checks to system  Agree supply improvement actions with owner/person responsible for the supply  Where E.coli persists in samples after improvements have been made, as actions in 2 above PLUS Discuss cause of failure  Size and nature of population at risk  Any currently known increase in GI illness Agree remedial action with LADiscuss boil water advice with LA and agree criteria for lifting the advice based on results & evidence that risks identified in risk assessment have been controlled as 2 above PLUS  HPU consider/continue enhanced surveillance for GI illness If re-samples pass as 2 above PLUS  LA revise supply risk assessment on completion of any improvement works

21 Shared guidance in NE


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