QMRAspot - a Tool for Quantitative Microbial Risk ... · 29 QMRA Dossiers (1st time historic data)...

1 QMRAspot | Bangalore | Feb 2012

QMRAspot - a Tool for Quantitative Microbial Risk Assessment from Surface Water to Potable Water

Jack Schijven

Peter Teunis

Saskia Rutjes

Martijn Bouwknegt

Ana Maria de Roda Husman


Content

1. Dutch Drinking Water Legislation and Implementation of QMRA

2. QMRA

3. QMRAspot


Content


2. QMRA

3. QMRAspot

QMRAspot | Bangalore | Feb 2012

Dutch Drinking Water Legislation and Implementation of QMRA

4

Dutch Drinking Water Act 2001

● No pathogens in drinking water ≠ zero => risk

● No detection of E. coli in 100 ml water ≠ safe water

● Quantitative Microbiological Risk Assessment (QMRA)

– WHO Drinking Water Guidelines: Health based target– http://www.who.int/water_sanitation_health/publications/2011/dwq_guidelines/en/index.html

– The Netherlands: Max infection risk = 10-4 per person per year

– Drinking water concentration ≈ 1 pathogen in 1 000 000 liter

● QMRA required for drinking water from surface water and vulnerable groundwater

● Index pathogens

– Enteroviruses, Campylobacter, Cryptosporidium, Giardia



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Environmental Inspectorate Guideline 5318 (2006)● How to do QMRA

● QMRA from surface water to drinking water

– Quality of source water (index pathogens)

– Treatment efficiency (indicator organisms)

● QMRA from vulnerable groundwater to drinking water

– Is protection zone of 60 days an adequate barrier (natural treatment)?

● Unconfined sandy aquifers and karst aquifers are vulnerable

– No protective confining (clay) layers

– Karst: fast flow paths

Index pathogens Indicator organismsEnteroviruses 20-200 nm Bacteriophages 20-60 nmCampylobacter 1-2 µm E.coli 1-2 µmCryptosporidium 5-6 µm Spores of sulphiteGiardia 8-10 µm reducing clostridia (SSRC) 1 µm



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QMRA evaluation

Drinking water companies

RIVMNational Institute for Public Health and the Environment

EnvironmentalInspectorate

QMRA dossier1st time: Historic data

New data every 3 years

QMRA reportRecommendations

DecisionIf not OK:

Extra treatment / more data

MEETING



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Overview Dutch drinking water companies

● 11 Drinking water companies

● 29 QMRA Dossiers (1st time historic data)

● 214 Production locations

84; 39%

97; 46%

9; 4%

7; 3%

4; 2%

13; 6%

A-unconfined aquifers

B-(semi)confined aquifers

I-groundwater recharge (dunes)

K-limestone aquifers

O-surface water

U-riverbank filtration


Content


2. QMRA

3. QMRAspot


QMRA

HAZARD IDENTIFICATION

EXPOSURE ASSESSMENT

DOSE RESPONSE RELATION

RISK CHARACTERIZATION


QMRA

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QMRA from surface water to drinking water

● Csw = Pathogen concentration in source water [N/liter]

● R = Recovery = fraction of detected pathogens [-]

● Z = Fraction of microorganisms passing treatment [-]

● Cdw = Pathogen concentration in drinking water [N/liter]

● V = Consumption of unboiled drinking water [liter]

● Pm = Infectivity of pathogen [-]

● Pinf = Infection risk [T-1]


QMRA

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Production (m3/day) Regular Peak events

<10 000 6 3

10 000-100 000 13 6

>100 000 26 9

Monitoring programme surface water

# of samples/3 years (conduct in 1 year)


QMRA

12



● River Rhine at Lobith:

1

10

100

1000

20-05-97 28-08-97 06-12-97 16-03-98 24-06-98Date

(oo)cysts/litreenteroviruses

/1000 litre

0

1000

2000

3000

4000

Flow ratem3s-1

CryptosporidiumGiardiaEnterovirusesFlow rate


QMRA

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WHO Guideline for Drinking Water Quality, 4th ed.


QMRA

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● Recovery data needed for each matrix and sample

Enterovirus 40-90% Rutjes et al, RIVM 3000 0007/2004

Campylobacter Most Probable Number

Cryptosporidium 0.7-88% Schets et al, RIVM 3000 0008/2004

Giardia 1.8-22% Schets et al, RIVM 3000 0008/2004


QMRA

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QMRA

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● Log10Z is log removal by treatment

● Required removal

– 4 – 8 log10– Depends on time and location

– Multiple barriers

● Disinfection

– UV, ozone, chlorine

● Filtration

– Membrane filtration, slow sand filtration, dune passage


QMRA

17

Drinking water treatment

● Disinfection

– Damages (kills) microorganisms

● Filtration

– Removes microorganisms

● Removal by treatment, example

– 99% is removed/killed/retained

– Fraction: 1% passes treatment

– Removal 2 log10● Source water (river, lake)

– 1-100 pathogens per liter

● NL-safe drinking water: maximum one pathogen per million liter

● Need a series of treatment: Multibarriers

– Commonly five to eight log removal


QMRA

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Disinfection

● Chlorine/ Chlorine dioxide

– Oxidization of organic matter

● Ozone (O3)

– Strong oxidization of organic matter

● UV

– Damages nucleic acid


QMRA

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QMRA

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QMRA

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Filtration

● Sieving / straining: pore size


QMRA

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Sand filtration● Inactivation

● Attachment/detachment

● Straining

--

- - -

Grain of sand

�

�

Attachment

Inactivation

Inactivation

Detachment

-

+----

-- +-

--

--

--

+

+-

---

-

-

-

--

-

--

-

--

---

-

--

--

-

---

- -

--

- --

--

-

--

-

- --

+

+

--


QMRA

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Sand filtration

● Rapid sand filtration

● Slow sand filtration

● River bank filtration

RiverTo WaterWorks

AlluvialAquifer


QMRA

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QMRA

25


QMRA

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QMRA

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● Log10Z is log removal by treatment

● Data of indicator organisms

1. Raw data: Counts and sample sizes before and after treatment

2. Location specific conditions

3. Full scale

4. Pilot plant scale

5. Laboratory scale

6. Literature data from other locations and scales


QMRA

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QMRA

29






● Cdw = Csw x 1/R x Z

● Csw ≈ 0.01 – 100 pathogens per liter

● Log10Z ≈ 4 – 8 log10● Cdw ≈ 10-6 pathogens per liter


QMRA

30










QMRA

31







● Average per person0.27 L/day

● Exposure = Dose D

– D = Cdw x V

– Numbersof ingestedpathogens/day


QMRA

32










QMRA

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QMRA from surface water to drinking water● Csw = Pathogen concentration in source water [N/liter]






● Not every pathogen particle causes an infection

● Pm = fraction of infectious particles(dose response relation,Teunis et al., Risk Analysis, 1999, 19:1251-260)

● Pm of enteroviruses highly variable

● Rotavirus most infectious virus


QMRA

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QMRA

35









● Pinf,day = Csw x 1/R x Z x V x Pm● Pinf,year = 365.25 x Pinf,day or

● Monte Carlo simulations (variability)

( )∏=

−−=365

1inf,inf, 11

idayyear i

PP


Content


2. QMRA

3. QMRAspot


QMRAspot

37

Microbiologic data for QMRA● Inspectorate Guideline 5318: QMRA every three years

● 1st time of QMRA

– Historic data

– Reports with detailed descriptions of drinking water production sites

● 2nd time of QMRA (2010-2012)

– New data from approved monitoring programs

● Raw data = unprocessed data

– Quantitative methods => Counts (N) and Sample sizes (V)

– Sample size: the actual analyzed size (volume) of the sample

– Most Probable Number: MPN-scheme (sample sizes) with 0 or 1

● Spreadsheet

– Scheme: Drinking water treatment and data selection

– Raw data in columns

– Set up after consulting drinking water companies

– Adaptation of LIMS

● Computational tool: QMRAspot


QMRAspot

38

REFERENCE

● QMRAspot

– Schijven JF, Teunis P, Rutjes S, Roda Husman AM de. QMRAspot: A computational user-friendly interactive tool for quantitative microbial risk assessment from surface water to drinking water.

Water Research, 10.1016/j.watres.2011.08.024 .


QMRAspot

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QMRA from surface water to potable water

● Mathematica notebook (Wolfram Inc, Champaign, Illinois, version 8)

● Runs in Mathematica and Mathematica Player Pro

● Two buttons

– Select file

– Run QMRA


QMRAspot

40

Select file:QMRAdata.xls

● Select and open a preformatted Excel spreadsheet with raw microbial data

�


QMRAspot

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QMRAdata.xls

● SCHEME

– Selections of RAW DATA

● RAW DATA

– Counts N

– Volumes V


QMRAspot

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Run QMRA

● Read the data from QMRAdata.xls

��


QMRAspot

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Run QMRA

● Read the data from QMRAdata.xls


QMRAspot

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Index pathogen source water concentration, Csw

● Last open water before treatment

● Sample scheme in relation with production capacity

● Regular sampling

● Peak events

● Counts and volumes: Negative Binomial [r,1/(1+λVi)]

● Concentrations:Gamma [r,λ]

�


QMRAspot

45

Recovery efficiency of detection method, R

● Preferably determined for each sample

● Paired spike and recovery data

● R: Beta [α,β], fraction (0-1)

● If no data R=1

�


QMRAspot

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Treatment Z1..6

● Unpaired influent and effluent data

● Beta [α,β], fraction (0-1)

● If only zero counts in influent then Z

i=1

● If only zero counts in effluent then Z

ican be

estimated as well

�


QMRAspot

47

Plots

● Time plots of concentrations of index pathogens of indicator organisms

● Plots include a line for the mean concentration and a coloured area encompassing 95% of all concentrations

● Concentrations higher than the 95-percentile are considered as peak concentrations

�


QMRAspot

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Monte Carlo data

● 10 000 samples from distributions from source water concentration and recovery

● Source water concentrationX1/Recovery=Corrected source water concentration

�


QMRAspot

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Monte Carlo data

● 10 000 samples from distributions from source water concentration and recovery

● Source water concentrationX1/Recovery=Corrected source water concentration


QMRAspot

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Monte Carlo data

● 10 000 samples from treatment distributions

● Total treatmentZtot = Z1 x … x Z6

�


QMRAspot

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Z1


QMRAspot

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Z2


QMRAspot

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Z3


QMRAspot

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Monte Carlo data

● Drinking water concentrationCdrw = Csource x 1/R x Ztot

● Consumption, W

● Exposure of dose, number of ingested pathogens per person per dayD = Cdrw x W

�


QMRAspot

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Monte Carlo data

● Drinking water concentrationCdrw = Csource x 1/R x Ztot

● Consumption, W

● Exposure of dose, number of ingested pathogens per person per dayD = Cdrw x W


QMRAspot

56

Infection risk, Pinf

● Per person per day

● α and β are infectivity parameters with between-strain variability

● Per person per year

( )∏=

−−=365

1inf,inf, 11

idayyear i

PP

( )DFPiday −+−= ;,1 11inf, βαα

�


QMRAspot

57


● Per person per day

● α and β are infectivity parameters with between-strain variability

● Per person per year

( )∏=

−−=365

1inf,inf, 11

idayyear i

PP

( )DFPiday −+−= ,,1 11inf, βαα


QMRAspot

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● BoxWhisker plots of infection risk per person per year for each index pathogen

● 95-percentile < 10-4 per person per year


QMRAspot

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Options● Index pathogens in

source water

● Distribution parameters instead of RAW DATA

● Values from literature

● RAW DATA preferred


QMRAspot

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Options● Removal of indicator

organisms by treatment

● Distribution parameters instead of RAW DATA

● Values from literature

● Database of distribution parameters for treatment steps as a function of process conditions


QMRAspot

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Options● Consumption of

unboiled drinking water

● Lognormal distributions for the Netherlands and the USA

● WHO: Fixed volume of 2 liter per person per day

● Or distribution parameters for any other country and/or for any other subpopulation (children, women, the elderly)


QMRAspot

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CONCLUSIONS

● Quick-and-clean QMRAin a few minutes

● For worldwide useby any stakeholder (environmental inspector, engineer, employee of drinking water company) without extensive knowledge about QMRA

● Options: Scenario studies

● Base for mitigation strategies, preventive measures, prioritization of measures

QMRAspot


QUESTIONS?

● QMRAspot is for free

● [email protected]

● [email protected]

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QMRAspot - a Tool for Quantitative Microbial Risk ... · 29 QMRA Dossiers (1st time historic data)...

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