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© Kiwa 2006 1
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Microbiological Risk Assessment
A scientific basis for managing drinking water safety from source to tap
www.microrisk.comMICRORISK
Know yoursource water
quality
Target yourtreatment
Safedrinking water
Know yourcatchment
Protect your distribution
© Kiwa 2006 2
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Microbiologically safe drinking waterCouncil directive 98/83/EC
Article 1. Objective is to protect human health from the adverse effects of any contamination by ensuring that it is wholesome and clean.
Article 4. Water is wholesome and clean if it is free from any micro-organisms and parasites and from any substances which, in numbers or concentrations, constitute a potential danger to human health
Operationally translated (Article 4) into meeting the requirements in Annex I.
Microbiological safety: E.coli 0/100ml (Clostridium perfringens 0/100ml) enterococci 0/100ml
© Kiwa 2006 3
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
E.coli as quality standardMilestone 1: culture media for bacteria
1885 - 1908 Professor Hygiene Berlin
1879: first proof of bacteria (anthrax) as agents of disease
1881: solid culture media for isolation of bacteria
1883: isolation of causative agent of cholera
1905: Nobelprice Physiology and Medicine
Robert Koch (1843-1910)
© Kiwa 2006 4
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
E.coli as quality standardMilestone 2: indicator-bacteria
1898 -1929Professor HygieneRU Utrecht
1904: Method for detection of fecal contamination of water with test at 46°C(Eijkman- test)
1929: Nobelprice Physiology and Medicine (discovery of role of vitamins)
Christiaan Eijkman (1858-1930)
© Kiwa 2006 5
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
The indicator concept
Presence of bacteria that are abundant in human and animal feces (E.coli, enterococci) in water indicates health risk (pathogens may be present)
Absence of indicator bacteria are indication of safety
© Kiwa 2006 6
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Connections to water supply and incidence of typhoid
0
10
20
30
40
50
60
70
1900 1910 1920 1930 1940 1950 1960 1970
30
40
50
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80
90
100
0
10
20
30
40
50
60
70
1900 1910 1920 1930 1940 1950 1960 1970
30
40
50
60
70
80
90
100% connection to mains supply% connection to mains supply
Cases of typhoid per 100000Cases of typhoid per 100000
© Kiwa 2006 7
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
E. coli has served us well, but….
Too late Outbreaks in absence of E. coli “New” pathogens more resistant Demonstrate due diligence: not retrospective but
proactive Consumer health & safety moving towards risk
approach (food safety) Scientific development of QMRA
WHO: Water Safety Plans IWA: Bonn charter
© Kiwa 2006 8
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Microbiological Risk Assessment
A scientific basis for managing drinking water safety from source to tap
www.microrisk.comMICRORISK
Know yoursource water
quality
Target yourtreatment
Safedrinking water
Know yourcatchment
Protect your distribution
© Kiwa 2006 9
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Objective
Provide scientific basis for QMRA
Develop a harmonised, evaluated and validated framework for risk assessment, providing adequate information for risk management
© Kiwa 2006 10
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Consortium Basic science - applied science - end users
Kiwa Water Research
Ondeo Services
Centre for Water and Wastewater Technology, Australia
Water Technology Centre
Technical University Delft
University of East Anglia
Anjou Recherche
Vivendi Water PartnershipInsitute for Hygiene, Univ. Bonn
Water Research Centre NSF
Institute for Infectious Disease Control
© Kiwa 2006 11
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Microrisk results
Scientific data on pathogen occurrence, efficiency of treatment processes, distribution system integrity, consumption of drinking water
QMRA using these data, (un)certainty assessment
Comparison between QMRA and epidemiological data on GI-illness/waterborne outbreaks
Protocol for QMRA, esp. exposure assessment
© Kiwa 2006 12
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
© Kiwa 2006 13
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Waterborne outbreaks in Europe 1990-2004
Pathogen Isolated in Cases
Bacterial Protozoal Viral Water Supply
Country No.
Outbreaks Campylobacter Shigella Cryptosporidium Giardia Norovirus
Viral (undete-rmined)
Mixed Pathogen
Gastroenteritis Ground- water
Surface Water
Mixed Not
Reported
Finland 12 4 - - - 6 1 - 1 10 2 - -
France 7 - - 2 - - - 3 2 5 - - 2
Germany 2 - - - 1 1 - - - 1 - - 1
Greece 3 - 2 - 1 - - - - 2 1 - -
Italy 1 - - - - - - - 1 - - - 1
Netherlands 1 - - - - - - - 1 1 - - -
Rep. Ireland 2 - - 1 - - - - 1 1 1 - -
Spain 6 1 1 1 - - - - 3 1 - 1 4
Sweden 7 3 - - - 1 - 1 2 3 3 - 1
UK (England) 29 - - 28 - - - - 1 5 14 4 6
UK (N.Ireland) 3 - - 3 - - - - - - 3 - -
UK (Scotland) 6 - - 5 - - - 1 - - 6 - -
UK (Wales) 1 1 - - - - - - - - - - 1
UK (unspecified) 6 - - 6 - - - - - 3 2 1 -
No. Outbreaks 86 9 3 46 2 8 1 5 12 32 32 6 16
Cases 72546 16222 531 7772 232 11408 2500 2511 31370* 43571 23047* 906 5022
© Kiwa 2006 14
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Fault tree analysis
Non-Micro.
Monitor. Failure
Response Failure Detection Failure
Compr./ Report Failure
Correct-ion
Failure
+ AND gate: Produces output if all inputs co-exist Inclusive OR gate: Produces output if one or more inputs exist
Top/Intermediate event: Represents undesirable event. Located within and at the tree top, antecedent events feed to this event
Transfer gate: Transfer in & out of inputs due to space limitations.
KEY
Filtration Failure
Treatment Failure
Source Water Contamination
Pre-Distribution Contamination
Monitoring
Micro. Monitor. Failure
Pathway
Temporary Disinfect-ion Failure
Chronic Filtration Failure
Source Pathway
+
Distribution System Contamination
Waterborne Outbreak
Commun-ication Failure
Drinking Water Contamination Detection & Response to Contamination
Temporary Filtration Failure
Disinfection Failure
Chronic Disinfect-ion Failure
Source
or
or
or
or or
or
or or
+
+
+
or
Base event: An initiating event which is located at the bottom of the tree.
© Kiwa 2006 15
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Factors causing the outbreaks
Source failure Rainfall 44% livestock activity 41% Sewage discharge 10%
Treatment Chronic filtration failure 38%
Distribution Backflow/cross connection 15%
Detection Failure to recognize problem 18%
© Kiwa 2006 16
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
CTS Locations
1
2
3
4 5
7
6
8
9
10
© Kiwa 2006 17
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Source water
© Kiwa 2006 18
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
WP2 Source water quality
Objective: design monitoring strategy for pathogens in raw water
Peak events are risk events, so include peak events in the strategy
First know your catchment, then design monitoring strategy.
Catchment survey (sources, contamination level, indicators for peak events)
Design and test monitoring strategy Several catchments, several pathogens
© Kiwa 2006 19
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
12 “Catchment to Tap Systems”
Distribution CTS Source water Treatment
Cl2 Pop. size 1 River Pre-O3 (Cl2 in summer) - Coa - Sed - RF - O3 - GAC - super/deCl2 Yes 224,000 2 Reservoir AR - RF - O3 - GAC – SSF No 440,000 3 River Pre -O3 - Coa - Sed - RF – O3 - GAC - Cl2 (3 systems) Yes 34,000 4 River Coa - Sed - O3 – GAC - Cl2 Yes 18,000 5 River with controlled intake Coa - Sed - O3 or Cl2 – GAC - Cl2 (2 systems) Yes 6 Reservoir Reservoir - Cl2 (summer) - Coa - Sed - GAC - Cl2 (2 systems) Yes
571,600
7 River Bank filtration – SSF - O3 – GAC Yes 120,000 8 Reservoirs Coa - Sed - RF - GAC - Cl2 Yes 50,000 9 Reservoir ( + river) RSF - O3 - GAC - SSF No 440,000
10 Mountain reservoirs Pre-Cl2 - Coa - Sed – RF – O3 - Cl2 Yes 47,600 11 Protected reservoirs DF - RF - Cl2/ClO2 Yes 300,000 12 Protected groundwater RF - Cl2 Yes 24,300
Coa =coagulation; Sed = sedimentation; RF is rapid filtration; O3 is ozonation; Cl2 is chlorination; ClO2 I schlorine dioxide; GAC is granular activated carbon filtration; AR is artificial recharge; SSF is slow sand filtration.
© Kiwa 2006 20
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Pathogens of interest
Parasites Cryptosporidium parvum Giardia intestinalis
Bacteria Campylobacter Escherichia Coli O157:H7
Virus Enterovirus Norovirus
© Kiwa 2006 21
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Catchment Survey
Objectives : Identification of pathogen sources and occurrence of peak events
Methodology: Location Description of water abstraction Description of the catchment
- Hydrogeology & Hydrology- Climate- Land use
Location & description of potential sources of faecal contamination
Human Origin Animal Origin
© Kiwa 2006 22
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Example for catchment description : CTS 3
Physical characteristics
0
40
80
120
Jan March May July Sept Nov
Pre
cip
ita
tio
n
0
5
10
15
20
Te
mp
era
ture
Average precipitation (mm)
Average temperature (°C)
45 m
910 m
Impervious
Pervious
Riv
er 1
Riv
er
2
Forests & meadows
Crops
Riv
er 1
Riv
er
2
20 Km
N
© Kiwa 2006 23
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Example for catchment description : CTS 3
Human activities
0
10
20
30
40
50
Nuclear power plant
Industry Agriculture Drinking water
Mm
3/a
n
Surface water Ground water
Water uses
Pathogen sources : animal breeding & WWTP
Bovine
Caprine
Poultry
Porcine
Ovine
WWTP 30 000 PE
WWTP 25 000 PE
WWTP 285 000 PE
WWTP 160 000 PE
Drinking water treatment plant
N
20 Km
© Kiwa 2006 24
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Example for catchment description : CTS 3
Occurrence of peak events Daily flow and turbidity 2002-2004
0
200
400
600
800
July-02 Jan-03 July-03 Jan-04
m3 /
s
0
50
100
150
200
NT
UFlowTurbidity r²=0,7
Peak relatively rare event (9 peaks per year # 25%)
Criteria : Qthreshold =147 m3/s & Tthreshold =12 NTU
© Kiwa 2006 25
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Raw water monitoring: what do we sample?
0
200
400
600
800
1 000
j f m a m j j a s o n d
Flow
m3 /s
Daily flow
Monthly flow
Annual flow (1918-2004)
Sample
CTS 3France
CTS 7Germany
Peak contamination
monitoring
© Kiwa 2006 26
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
High bird loads
© Kiwa 2006 27
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Campylobacter in off-stream storage reservoir water (1994 & 2001)
0.1
1
10
100
1000
J F M A M J J A S O N D
Month
Nu
mb
er
(MP
N/l)
2001
1994
© Kiwa 2006 28
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Bird counts on reservoir
Totaal aantal dominante vogels op de Petrusplaat 1994
0
500
1000
1500
2000
2500
3000
3500
09-02-94
23-02-94
09-03-94
23-03-94
06-04-94
20-04-94
04-05-94
18-05-94
01-06-94
15-06-94
29-06-94
13-07-94
27-07-94
10-08-94
24-08-94
07-09-94
21-09-94
05-10-94
19-10-94
02-11-94
16-11-94
30-11-94
14-12-94
28-12-94
11-01-95
25-01-95
Kuifeend Smient Wilde eend Meerkoet Fuut Krakeend Wintertaling Slobeend
© Kiwa 2006 29
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Pathogens in source water summary
Baseline contamination Rain event contamination
Faecal indicators
E. coli 102-104 MPN/L 103-104 MPN/L and up to 50,000 MPN/L
Clostridia 3000 n/L and up to 17,500 n/L 5,000-6,000 n/L
Enterococci 102-103 n/L > 103 n/L
Total Coliforms 103-105 MPN/L 30,000-130,000 MPN/L
Pathogens
Cryptosporidium 0.05-0.5 n/L and up to 4.6 n/L Concentrations not clearly higher
Giardia 0.01-1 n/L and over 40 n/L in one case Concentrations not clearly higher
Campylobacter 0-100 MPN/L but up to 15,000 in one case Concentrations not clearly higher
E. coli 0157:H7 10-100 CFU/L and up to >1,000 CFU/L Concentrations not clearly higher
Enterovirus Rarely detected 300 n/L in one CTS
Norovirus Not detected (one CTS tested) 150 n/L in one CTS
© Kiwa 2006 30
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Conclusion
Quantitative Microbiological Risk Assessment (QMRA)
Know your catchment (survey it) in order to:Identify pathogen sources
Occurrence and frequency of peak events
Monitor your catchment in order to assess:Chronic contamination
Magnitude of peak events
© Kiwa 2006 31
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
WP3 Treatment efficiency
Objective: design strategy to describe and control treatment efficiency (QMRA and Water Safety Plan)
Describe treatment efficiency (QMRA) Collect and review state-of-the-art Full scale indicator bacteria Full scale porcess parameters Pilot plant research
© Kiwa 2006 32
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Treatment framework
Literature reviewMean Elimination Capacity
MEC
Reduction creditsBased on unit processes
Estimated pathogen elimination
4.2.2 4.2.2 4.2.3 4.2.4 4.2.5 4.2.64.2.7
© Kiwa 2006 33
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Tier 1: Log credits
MIN DEC MAX DECMEC
Efficacy of treatment process in literature(7 studies for one pathogen and one process)
No site infoNot disinfection
© Kiwa 2006 34
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Tier 1: Log credits Quantify UNCERTAINTY
MIN DEC MAX DECMEC
Apply triangular PDF
No site infoNot disinfection
© Kiwa 2006 35
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Tier 2: Refine based on turb or design
MIN DEC MAX DECMEC
POOR GOOD
0
0.5
1
1.5
2
2.5
3
Jan 2001 Jan 2002 Jan 2003 Jan 2004 Jan 2005
Tu
rbid
ity
NT
U
Raw waterFiltrate
0.01
0.1
1
10
100
Jun 1999 Jun 2000 Jun 2001 Jun 2002 Jun 2003
Tu
rbid
ity
(NT
U)
Source
Treated
© Kiwa 2006 36
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Treatment framework
Literature reviewMean Elimination Capacity
MEC
Reduction creditsBased on unit processes
Estimated pathogen elimination
DesignCharacteristics
Specific MEC
4.2.2 4.2.2 4.2.3 4.2.4 4.2.5 4.2.64.2.7
© Kiwa 2006 37
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Model from pilots and literature
Inactivation of E-coli
0
1
2
3
4
5
6
7
0 0.5 1 1.5 2 2.5 3
Ct (mg*l/min)
DE
Escherichia coli ( Finch, G.R. 1988 ) Escherichia coli ( Restaino, Lawrence 1995 )
Escherichia coli ( Zhou, H. 1994 ) HOM model 20°C
HOM model 5°C
© Kiwa 2006 38
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Treatment models
0
5
10
15
20
25
28-10-1995 11-3-1997 24-7-1998 6-12-1999 19-4-2001 1-9-2002
T0
0.5
1
1.5
2
2.5
28-10-1995 11-3-1997 24-7-1998 6-12-1999 19-4-2001 1-9-2002
Ct
0
2
4
6
8
28-10-1995 11-3-1997 24-7-1998 6-12-1999 19-4-2001 1-9-2002
DE
0
20
40
60
80
28-10-1995 11-3-1997 24-7-1998 6-12-1999 19-4-2001 1-9-2002
Co
li44
in
0.00000001
0.000001
0.0001
0.01
1
28-10-1995 11-3-1997 24-7-1998 6-12-1999 19-4-2001 1-9-2002
Co
li44
ou
t
Temperature
Ct
DE (log removal)
Coli untreated
Coli treated
&
=
*
=
© Kiwa 2006 39
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Treatment framework
Literature reviewMean Elimination Capacity
MEC
Full-scale measurementsVariation of process
Conditions at full scale
Reduction creditsBased on unit processes
(On-line) Residuals
Model Disinfection +Identify events
Estimated pathogen elimination
DesignCharacteristics
Specific MEC
(On-line) Surrogate
Refine MEC+Identify events
4.2.2 4.2.2 4.2.3 4.2.4 4.2.5 4.2.64.2.7
© Kiwa 2006 40
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Ruwwaterverdeelbak DynaSandfiltersBufferreservoir
Ozondesinfektie
3 / 4
Ozondesinfektie
1 / 2
W EDSF
SnelfiltersLoenderveen
W 1500
Ontharding
Koolfilterstraat 1 Koolfilterstraat 2 Koolfilterstraat 3
LZF straat 2 LZF straat 1
Reinwaterreservoir 2 Reinwaterreservoir 1
POMPW 7100
W 7010 W 7009
W 6823 W 6821
W 67K83W 67K82W 67K81
W 6440
W 6013 W 6012
W 6313 W 6312
W 6007
W 6005
OntrekkingW aterleidingplas
W 1110
© Kiwa 2006 41
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Clostridium spore removal over time
0,1
1,0
10,0
100,0
0 200 400 600 800 1000 1200-> days
SS
RC
per
10
0ml
Influent
Effluent
Days
100
10
1
0.11200200 600400 10008000
SSRC per 100 mlInfluent Effluent
Days
100
10
1
0.11200200 600400 10008000 1200200 600400 10008000
SSRC per 100 mlInfluent EffluentInfluent Effluent
CoagulationCoagulation
OzoneOzone
© Kiwa 2006 42
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Lab is not practice: ozone example
Ozonation CT 2 mg.min/l Expected E. coli inactivation: >>5 logs Full scale E. coli data:
- E. coli present in 4% of samples after ozone- Removal 2.7 log
0.01
0.1
1
10
100
1000
Dec-02 Mar-03 Jun-03 Oct-03 Jan-04 Apr-04 Aug-04 Nov-04
E. coli
concentr
atio
n (
CF
P/l)
Ozone in
Ozone out
© Kiwa 2006 43
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Bad days: example of chlorination: inactivation modelled on CT, hydraulics and temperature
0
0.5
1
1.5
2
2.5
3
3.5
27 Apr 07 May 17 May 27 May 06 Jun 16 Jun
Log
ina
ctiv
atio
n
© Kiwa 2006 44
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Pilot studies: Cryptosporidium removal by pilot slow sand filter
0.001
0.01
0.1
1
10
100
1000
10000
0 50 100 150 200 250Looptijd (dagen)
Co
nce
ntr
ati
e (
n/l
)
Influent
Effluent
Effluent < analysegrens
Geen meting mogelijk door neerslag
Dag 28 - 35 zonder dosering
© Kiwa 2006 45
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Treatment processes log removal
Coagulation-Sedimentation-Filtration-GAC filtration-Chlorination- 4.3
Coagulation-Sedimentation-Filtration-GAC filtration-Ozone-Chlorination- 4.3
Coagulation-Sedimentation-Filtration-GAC filtration-Chlorination- 3.4
Coagulation-Sedimentation-Filtration-GAC filtration-Chlorination- 3.3
Impoundment-Coagulation-Sedimentation-Dissolved Air Flotation-Filtration-GAC filtration-Chlorination-
3.2
Impoundment-Coagulation-Sedimentation-Filtration-GAC filtration-Chlorination- 3.2
Coagulation-Sedimentation-GAC filtration-Ozone-Chlorination- 3.1
Coagulation-Sedimentation-Filtration-GAC filtration-Chlorination- 2.6
UK Crypto data: Treatment
© Kiwa 2006 46
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Treatment framework
Literature reviewMean Elimination Capacity
MEC
Full-scale measurementsVariation of process
Conditions at full scale
Reduction creditsBased on unit processes
(On-line) Residuals
Model Disinfection +Identify events
Estimated pathogen elimination
Full-scale samplesPathogenic and indicator
organisms before andafter treatment
Stochastic model
IndicatorsTranslate toPathogens
PathogensDirect
Analysis
CombinedIndicators and
Pathogens
DesignCharacteristics
Specific MEC
(On-line) Surrogate
Refine MEC+Identify events
4.2.2 4.2.2 4.2.3 4.2.4 4.2.5 4.2.64.2.7
Available dataSite specific
© Kiwa 2006 47
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Total treatment Monte Carlo
© Kiwa 2006 48
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Distribution
© Kiwa 2006 49
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Distribution
Faecal contamination incidents Netherlands 1994 – 2003 7 water companies 11 million people supplied 50 incidents reported 5 - 50,000 people affected per incident
Probability of being affected by incident:
1.7 x 10-3 pppy
© Kiwa 2006 50
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Distribution incidents: duration
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-10 0 10 20 30 40 50 60
Duration (days)
CD
F p
erc
en
tile
s (%
of
inc
ide
nts
wit
h d
ura
tio
n <
= x
)
From detection (day 0) to end of incidentFrom cause to detection (day 0) of incident
From detection (day 0) to protective measuresPeak of E. coli concentration
© Kiwa 2006 51
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Distribution incidents: magnitude
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0.01 0.1 1 10 100 1000
E. coli concentration (CFP per 100 ml)
CD
F p
erc
en
tile
s (
% o
f in
cid
en
ts w
ith
[E
. co
li]
<=
x)
Mean
90-percentile
Maximum
First sample
© Kiwa 2006 52
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Translation to pathogens
E. coli data in distribution network No pathogen data
E. coli AND pathogen data in sewage Assume: contamination source is sewage Use pathogen to E. coli ratio’s to translate E. coli to
pathogens
Sensitivity analysis: Pathogen/E.coli ratío from different matrices
© Kiwa 2006 53
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Microrisk WP5: consumption
How much cold tap water do we consume?
What information is available? How reliable/useful is the available
information? How is tap water consumption
distributed? Can we come to a useful estimate for
QMRA?
literature review
statistical analysis of data
© Kiwa 2006 54
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Literature review
Review available studies on tap water consumption > 25 studies found
Evaluate design of the studies Way of recording consumption Factors that might influence tap water consumption
USA Nl Ger Fr S UK Aus Can Italy0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
con
sum
ed c
old
ta
p w
ate
r (l
/da
y)
© Kiwa 2006 55
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Study design
(24h-) Dietary recall Retrospective Interview/questionnaire Measures recent consumption
Dietary record/diary Prospective Measures current consumption
Food frequency questionnaire Retrospective Consumption in general
Combination of questionnaire & diary
© Kiwa 2006 56
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Literature review: results
Tap water consumption average consumer Cold tap water: 0.2 - 1.55 L/day Total tap water: 0.71 - 2.58 L/day
Comparibility influenced by: Population participating Year of survey Season of data collection Method of data collection Method to assess volume tap water consumed Types of water included
No conclusions regarding effects of age, season, gender on tap water consumption
Physical activity, income and perceived health status were reported to increase consumption
© Kiwa 2006 57
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Australia
Final: case-control study sporadic cryptosporidiosis Melbourne & Adelaide (Q) (N = 950, N = 644)
Melbourne best performance Poisson distr. Adelaide: again Poisson best, but poor similarity of shape Nr of non-consumers higher than nr consuming 1 glass Diary study in pilot most valuable
0 2 4 6 8 10 12 0%
5%
10%
15%
20%
25%Melbourne study
consumption (#glasses/ day)
rela
tive
fre
quen
cy o
ccur
ence
s
Empir ical data
Poisson
Exponential
Gamma
Log-normal
0 2 4 6 8 10 12 0%
5%
10%
15%
20%
25%
Adelaide study
consumption (#glasses/ day)re
lati
ve f
requ
ency
occ
uren
ces
Empir ical data
Poisson
Exponential
Gamma
Log-normal
© Kiwa 2006 58
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Recommendations for QMRA
Use country specific data and distributions (when available) Use mean as conservative approach, instead of median (skewed
distribution) Beware for inter-country AND intra-country differences (Adelaide
vs Melbourne) Several datasets available? Use data generated with best study
design Otherwise: use highest consumption estimates as conservative
approach (data Melbourne)
© Kiwa 2006 59
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Risk assessment
© Kiwa 2006 60
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
WP6 Risk assessment
Objective: protocol for risk assessment (integration of WP2-5 and dose-response data) and protocol for uncertainty analysis
Select most appropriate mathematical techniques for integration of information into risk assessment
Include uncertainty analysis into protocol
Case studies: evaluate protocol: determine risk and uncertainty level
© Kiwa 2006 61
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Conceptual model
© Kiwa 2006 62
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
QMRA design
Stage/Barrier Functions and Coefficients Describing Stages and Barriers Input Source Water Dry weather concentration Campylobacter.L-1 described by a lognormal PDF with coefficients:
µ (log10) = 1.46; sigma (log10)= 1.85 Wet weather Campylobacter.L-1 concentration described by a Gamma PDF distribution with coefficients: alpha = 1.98; beta = 24.7 Proportion of time in dry weather based on flow analysis: Spring = 0.16; Summer = 0.017; Autumn =0.065; Winter = 0.329
Barrier A (Reservoir) Point estimates for seasonal decimal (log10) elimination capacity (DEC’s) were: Spring = 2.69; Summer = 2.46; Autumn =2.16; Winter = 2.37 These reductions were averaged to generate the reduction figure used.
Barrier B (Coagulation + Flocculation + DAF)
DEC described by a normal PDF: µ = 2.38; sigma = 0.38 Decimal (i.e. log10) reduction statistics are: 5th percentile = 1.75; Mode = 2.38; 95th percentile = 3.00
Barrier C (Rapid Sand Filter)
DEC described by a normal PDF: µ = 1.12; sigma = 0.40 Decimal (i.e. log10) reduction statistics are: 5th percentile = 0.46; Mode = 1.12; 95th percentile = 1.78
Barrier D (Chlorination + Short term storage)
Complex DEC with the following statistics: 5th percentile = 3.49; Mode = 3.88; 95th percentile = 6.53 Coefficients and inputs used in reduction calculation were: A = 6.31E9; E = 48699; R = 8.314; T = 273 + Temperature in oC where oC was obtained by re-sampling of a table of percentiles of water temperature entering the water treatment plant ; [Cl2] mg.L-1 = lognormal PDF with (µ = 3.86, sigma = 0.44, correction factor = -2.13); Fraction of storage volume = 0.1*beta function; Flow (ML.d-1) = resample of percentile lookup table of flows into the plant.
Consumption PDF of litres consumed per day per person described by Poisson distribution with the following coefficient: Gamma = 2.86 Consumption PDF has the following statistics: 5th percentile = 0 L; Mode = 0.75 L; 95th percentile = 1.5 L
Dose-response Variation on beta Poisson where dose is always 0 or 1: Prob. of infection (P) =e(-(alpha/(alpha + beta))*Dose) Where beta = 0.011 and alpha =0.024 The Maximum likelihood curve is: P=1-e(-Dose)
© Kiwa 2006 63
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Monte Carlo
© Kiwa 2006 64
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Statistical data analysis - outputProbability of infection
© Kiwa 2006 65
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Sensitivity analysis
]inf[
]inf[10 ExpectedP
WorstCasePLogitivityFactorSens
5.0% 95.0%
Expected Value
Worst Case
© Kiwa 2006 66
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Factor Sensitivity Results - Adelaide
Parameter Expected Value
Worst Case Factor Sensitivity
Source Water Concentration (oocyst.L-1)
0.2 5 1.40
Flow Rate (m3.s-1) 0.15 1 0.82
EMC (oocyst.L-1) 2.25 50 1.32
Event Volume (ML) 213 500 0.02
Reservoir Dilution Factor 9 6 0.18
Treatment Removal 4.5 2 2.50
Consumption 1 4 0.60
Event/Nominal 4.26
© Kiwa 2006 67
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Effect of chlorination failure time
1.00E-06
1.00E-05
1.00E-04
1.00E-03
1.00E-02
1.00E-01
1.00E+00
0.001 0.01 0.1 1 10 100 1000
Duration of Event (days)
Pro
b.
infe
ctio
n/p
ers
on
/y
Average
Median
95th percentile
99th percentile
(0)
© Kiwa 2006 68
EU-5th Framework program: Energy, environment and sustainable development; project EVK1-CT-2002-00123: MICRORISK
Microbiological Risk Assessment
A scientific basis for managing drinking water safety from source to tap
www.microrisk.comMICRORISK
Know yoursource water
quality
Target yourtreatment
Safedrinking water
Know yourcatchment
Protect your distribution