The Health Protection Agency - Northumbrian Water

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The Health Protection Agency - Northumbrian Water Powered By Docstoc
					Guidance for Responding
to Drinking Water Quality Failures
in the
North East of England, March 2012
Liz Stokle
Senior Health Protection Nurse
North East Health Protection Unit
 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. 
Challenges for risk

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
Challenges for risk

Raw water abstraction
Treated water 
Nature of problem/failure
Chemical and microbiological parameters
Microbiological parameters

Indicator Organisms
Faecal indicators:
Multiple variables

Alone or in conjunction with other organisms such 
   as E.coli

Small numbers or high numbers
Other biological & chemical

Chlorine or lack of
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)
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
Contextual issues

 Point of failure

 Nature of failure

 Size of population affected

 Nature of population affected

 Current awareness of GI illness
 Challenges for protecting
 health of population

Interpreting the information/evidence 

Risk assessment appropriate to context

Implementing proportionate response
Launch of document
 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
Failure of Prescribed       LA first response                                                                   HPA first response                                                                    Standard response
Concentration or Value      (response should be initiated at presumptive stage within 1 working day of          (response should be initiated at presumptive stage within 1 working day of            (within 1 month)
(PCV)                       receipt of event notification)                                                      receipt of event notification)

1. Coliforms 1-50 per       Discuss circumstances and context of failure with NWL/HW e.g. burst main,           Discuss circumstances and context of failure with NWL/HW e.g. burst main,                     NWL/HW to report 
100ml in the ABSENCE        contamination at service reservoir:                                                 contamination at service reservoir:                                                            outcome of any follow
of                                  Assess: chlorine levels, cause of failure, population at risk & any                Assess: chlorine levels, cause of failure, population at risk & any                   -up samples as soon 
E. coli (otherwise action            currently known increase in gastrointestinal illness                                currently known increase in gastrointestinal illness via current HPU                  as available
as for E.coli)                      Consider whether site visit to implicated location is necessary (may                surveillance systems
                                     involve liaison with other LAs & water company for access if wide                  Agree NWL/HW actions 
                                     distribution area affected)
                                    Agree NWL/HW actions

1a. Coliforms >50 per       Value >50 coliforms with or without E.coli is an indication of poor quality         Value >50 coliforms with or without E.coli is an indication of poor quality                   NWL/HW to report 
100ml in the ABSENCE        drinking water                                                                      drinking water                                                                                 outcome of any follow
of                          As above PLUS                                                                       As above PLUS                                                                                  -up samples as soon 
E. coli (otherwise action           Any abnormal changes in colony counts                                              Any abnormal changes in colony counts                                                 as available
as for E.coli)                      Agree measures to investigate ‘integrity of the system’                            Agree measures to investigate ‘integrity of the system’
                                    Agree with Water supplier further investigations for faecal                        Agree with Water supplier further investigations for faecal 
                                     contamination                                                                       contamination

2. E.coli 1–10 per 100ml    As above PLUS consider if ‘boil water’ advice should be issued                      As above PLUS consider if ‘boil water’ advice should be issued and document           As above PLUS
(without coliforms or               If ‘boil water’ advice agreed, also agree conditions required to remove    rationale                                                                                     NWL/HW remove ‘boil 
with coliforms up to a               the boil water notice                                                                If ‘boil water’ advice agreed, also agree conditions required to remove             water’ advice when 
level of 50)                                                                                                               the boil water advice                                                               agreed conditions 

3. E. coli >10 per 100ml    As above PLUS consider immediate check sampling                                     As above PLUS discuss context & boil water advice 
(especially where                 from consumers taps in affected area to verify   
coliforms >50)                    NWL/HW bacterial sample results

4. Cryptosporidium          Discuss context of failure in relation to extra evidence of risk i.e. aware of:     Discuss context of failure in relation to extra evidence i.e. aware of:               As above PLUS
oocysts (any number)                 Cluster/increase in cases in affected area                                         Cluster/increase in cases in affected area                                          NWL/HW Remove 
and/or report of                     Ingress at treatment works or in distribution network                              Ingress at treatment works or in distribution network                                ‘boil water’ advice 
turbidity >1 NTU at                  Treatment failure or turbidity failure in treated water                            Treatment failure or turbidity failure in treated water                              when agreed 
water treatment works       Where no extra evidence of risk (as described above) and failure level low          Where no extra evidence of risk (as described above) and failure level low                     conditions achieved
or >4 NTUs at customer      i.e. <1 oocyst/10 litres                                                            i.e. <1 oocyst/10 litres                                                                      HPU enhanced 
tap                                  Agree action for resampling and investigation of cause                             Agree action for resampling and investigation of cause                               surveillance for 
(Continued over)            Where extra evidence of risk exists (as described above) and/or failure             Where extra evidence of risk exists (as described above) and/or failure                        increase in 
                            significant numbers i.e. >1 oocyst/10 litres in treated water                       significant numbers i.e. >1 oocyst/10 litres in treated water. Discuss with                    community cases
                                     Consider boil water advice with NWL/HW                                    senior to:                                                                                    NWL/HW to report 
                                     Agree conditions required to remove the boil water notice                          Consider boil water advice with NWL/HW                                               outcome of 
                                     Alert EHO colleagues to be vigilant for cases                                      Agree conditions required to remove the boil water advice                            investigation 
                                                                                                                         Alert HPU staff to enhanced surveillance for cases
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
Failure of   LA first response                        HPA first response                    Standard
Prescribe    (response should be initiated at         (response should be initiated at      response
d            presumptive stage within 1               presumptive stage within 1            (within 1 
Concentra    working day of receipt of event          working day of receipt of event       month)
tion or      notification)                            notification)
1.           Discuss circumstances and                Discuss circumstances and                 NWL/HW 
Coliforms    context of failure with NWL/HW           context of failure with NWL/HW             to report 
1-50 per     e.g. burst main, contamination           e.g. burst main, contamination             outcome 
100ml in     at service reservoir:                    at service reservoir:                      of any 
the           Assess: chlorine levels, cause          Assess: chlorine levels, cause           follow-up 
ABSENCE           of failure, population at risk &         of failure, population at risk &      samples 
of                any currently known increase             any currently known increase          as soon 
E. coli           in gastrointestinal illness              in gastrointestinal illness via       as 
(otherwis     Consider whether site visit to              current HPU surveillance              available
e action          implicated location is                   systems
as for            necessary (may involve               Agree NWL/HW actions 
E.coli)           liaison with other LAs & water 
                  company for access if wide 
                  distribution area affected)
              Agree NWL/HW actions
   Table 2 : Response to failures of private
   water samples
Type of Failure                                                                 Local Authority                                                HPA first response                  Long term response LA and/or HPU as indicated
- of Prescribed Concentration or            First response                               Standard response (within 1 month of       (on receipt of notification from LA unless     (> 1 month and up to the 5 year review of the supply 
Value (PCV)                                 (within 3 working days of receipt of result  last result)                               otherwise stated)                                              risk assessment)
                                            unless otherwise stated)                     Consider serving notice under
                                                                                         regulation 18

1. Coliforms 1-5 per100ml in the                    Inform owner/person                        Undertake an investigation         HPU not informed                               LA revise supply risk assessment 
ASBSENCE of                                          responsible for supply & advise             and/or risk assessment
E. coli (if E. coli present action as for            on improvements & checks to                Provide further advice on any  
E. coli below)                                       system                                      improvements required based 
                                                                                                 on risk assessment

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

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

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

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

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