Microbiologische risico s van drinkwater

Patrick Smeets, 1 Oktober 2007

Partner for progress

Microbiologische risico’s van drinkwater TU Delft

Drinkwater is toch veilig?

© Kiwa Water Research 2006

2

Microbiologische risico’s in ontwikkelde landen door ‘Ongelukken’ 1993

2000

2001

Milwaukee, USA Change in treatment plant operation resulted in Cryptosporidium in water

403,000 people ill 4,400 hospitalised 100 people died Walkerton, E.coli 0157H7 and Campylobacter in water due 2,300 people ill Canada to operational errors 65 hospitalised 7 people died Belfast, Northern 9 potential sources of contamination comprised 191 cases of cryptosporidiosis, Ireland the supply; sewage backflow was considered the 41 hospitalisations. main cause.

2002

Northeast Italy

2002

Ski resort, Sweden

2003

Divonne-lesBains, Ain district, France

2007 2007

Galway, Ireland Contamination with cryptosporidium Spencer, USA Human error put lye in water


Broken sewer pipe in football field irrigation 670 reported gastrointestinal system allowed water from Bacchiglione River to illness (GI). 32 cases were enter city aqueduct. referred to hospital, 6/32 were admitted. Unchlorinated groundwater (GW) source. Crack 9/12 stool samples positive for NLV. Estimated 500 cases in the in sewage pipe located 10m from a well population. supplying system. Cross-connection between STP effluent network 786 suffered GI. Multiple and distribution system; chronic contamination of enteropathogens identified, water source and inadequate treatment 2 people were hospitalised, 60 people hospitalised 100 people medical attention at least 1 hospitalised 3

Microbiologische risico’s in ontwikkelde landen ‘Terrorisme’ (nog niet microbiologisch) year

location

2002

Rome, Italy

2003

China

2003

Prague, Czech Republic Carpentersville, USA Lake Constance, Germany Blackstone, USA

2004 2005 2006


Incident public health effect Intentional threats and contamination incidents no, offenders arrested Plot to break in through water pipes into American Embassy Poisoning of water reservoir with 42 people hospitalised pesticides Threat of poisoning with mercury no, blackmailer arrested and cyanide Vandals spray fire extinguishers in no, filtration unit was not in filtration unit use 10 litres of atrazin dropped near no, because of low solubility water intake and low toxicity of atrazin Vandals break into a water storage no, drinking water ban tank proclaimed

4

Cholera in ontwikkelingslanden neemt weer toe!


5

Wat zijn de risico’s en waar komen ze vandaan

Virussen

Bacteriën

Protozoa

Overige microbiologische risico’s: prionen, wormen, toxines …

Oorsprong: Uit fecaliën van mens en dier (E. coli O157, norovirus, Cryptosporidium ….) Groeien in het milieu of in drinkwater (legionella) © Kiwa Water Research 2006

6

Verontreinigingsbronnen oppervlaktewater

Wastewater


Recreation

Wildlife

7

Wat zijn de gevolgen

Darmklachten, diaree, overgeven, misselijk… Ernstig bij gevoelige groepen (onderdrukt imuumsysteem) Soms ook ernstige effecten, bijvoorbeeld Guillain-Barré syndrome (verlamming door Campylobacter) Dood


8

Hoe veilig moet drinkwater zijn?

Géén indicatorbacteriën (E. coli) in 100 ml monster Kans op infectie <1/10.000 per jaar Hoe toon je aan dat het water veilig is? Analyse onmogelijk

Pathogens in source © Kiwa Water Research 2006

Removal by treatment

Pathogens in drinking water

Risk of infection 9

Internationaal project over risico-analyse MicroRisk

Swedish Institute for Infectious Disease Control

WRc-NSF Ltd

Partner for progress

2002-2006 11 Partijen 7 landen © Kiwa Water Research 2006

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QMRA for drinking water Quantitative Microbiological Risk Assessment

Source

Monitor

100 /L 0

Sedimentation

1 log

500

10 /L 0

Filtration Disinfection

2 log 2 log

1

0.1 /L 0.001 /L

0

1

0

Distribution

No cont.

0.001 /L

Consumption

1L

0.001 /d

Dose-Response

10%

*0.1

Risk of infection

0 2 4 6 8

0

1

- 1 .4

- 0 .5

1000

0.0001 inf/d - 4 .0


1

- 3 .1

- 2 .2

11

Meten in de bron

Véél verschillende pathogene micro-organismen Analysemethoden moeilijk en duur Onzekerheden: Variatie: hoe hoog zijn piek concentraties? Recovery: welk percentage toon je aan? Type: is deze variant gevaarlijk voor de mens?


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Hoeveel micro-organismen zitten in het monster?

Gemiddeld 3 organismen in een monstervolume Waarneming varieert echter van 0 tot 7 © Kiwa Water Research 2006

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Drinkwaterzuivering

Rapid Sand Filtration

OZONE

Slow Sand Filtration

Meervoudige barrières tegen micro-organismen © Kiwa Water Research 2006

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Verwijdering door de zuivering Hoe kwantificeer je dat?

Literatuuronderzoek Processen experimenteren Processen modelleren Metingen in de praktijk


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Experimenteren Inactivatie door ozonisatie

5 4.5

Log inactivation inactivation Log

4 3.5 33 2.5 2.5 2 2 1.5 1.5 1 1 0.5 0.5 0 0 00

0.05 0.05

0.1 0.1

0.15 0.15

Ct Ct (mg*min/l) (mg*min/l) cultured Fresh Fresh cultured cultured Stress. water Freshsterile cultured Stress. sterile water Stress. sterile 6 m. old + env.water water


Stress. environm. water Stress. Stress.environm. environm.water water 6 months old water Stress. environm. 6 months old Environmental

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Modelleren Model wel verifiëren met de werkelijkheid! E. coli at 10°C 10

T10

DE (Log inactivation)

9 8 7

PLUGFLOW

6 5 4 3

CSTR

2 1 0 0

0.5 1 1.5 Observed Ct (m g*l/m in)

T10 T10 T10 lab E.coli lab E.coli CSTR nat. E.CSTR colilCSTR Sample negative

2

MIXED

CSTR lab E.coli CSTRpositive nat. E. colil Sample

Verified at full-scale © Kiwa Water Research 2006

17

Meten in de praktijk Invloed van variaties en metingen

Treatment processes can retain and release organisms over time!

A sample only represents a very small portion of the water during a short moment in time!


sand filter 18

Denken in logeenheden 2 log=99%verwijdering 2 log

10 filters Elk 2 log verwijdering 1 faalt

2 log

100 CFU/L

2 log

2 log 0 log

2 log 2 log 2 log 2 log 2 log © Kiwa Water Research 2006

1 CFU/L 1 1 100 1 1 1 1 1

109 10 =11 CFU/L

concentratie in filtraat: A ≈ 100 CFU/L B ≈ 10 CFU/L C ≈ 1 CFU/L D ≈ 10-16 CFU/L

1 19

Lekkage bij distributie E. coli in 0.1% van de monsters


20

Drinkwaterconsumptie

Telefonisch interview (‘recall’) Dagboek


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Kans op infectie Dosis-respons Wat is de kans dat je een infectie ontwikkelt wanneer je één of meer micro-organismen binnen krijgt? Relatie vaststellen met: 10 0

Vrijwilligers (studenten) Uitbraken Yearly risk of infection

Maximum=100%

-1

10

-2

10

-3

10

Human feeding trial Outbreak Maximum risk curve

-4

10

-4

10


-2

10

0

10 Dose org/d

2

4

10

10

22

Monte Carlo analyse

30%

RAW

25%

20% 15%

10%

30.0% 5%

25.0%

51 10 2 20 5 41 0 81 9 16 38 32 77

13

26

6. 4

1. 6 3. 2

0. 4

0. 8

0. 1 0. 2

0. 05

0%

Campylobacter MPN/l

Data

20.0% 15.0%

CONCENTRATION AFTER RSF

MLE PDF 10.0%

30.0%

5.0%

REMOVAL RSF

1

Data 10.0%

5.0%

0

8

1. 00

9

0. 77

6

0. 51

0. 34

4

1

0. 23

3

0. 15

0. 10

8

0. 06

6

0

0. 04

0. 03

0

4

0. 02

0. 01

9

6

0. 00

4

0. 00

0. 00

0. 00

3

0.0%

Fraction passed RSF

Data

MLE PDF


23

85

5

Campylobacter concentration after RSF

15.0%

10

47

20

39

89

17

20.0%

1. 4 3. 2 7. 3

0.0% 0. 00 2 0. 00 4 0. 00 9 0. 02 1 0. 04 9 0. 11 0. 26 0. 60

25.0%

Resultaat: FN-curve

Ruwwater Na filtratie Na ozonisatie


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Wat doe je met het resultaat?

Zuiveringsstappen toevoegen? Bedrijfsvoering veranderen Meer ozon of chloor doseren Sturing verbeteren Filtratieprocessen optimaliseren …..

Meer meten? Huidige situatie handhaven en borgen


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Proces en/of bedrijfsvoering verbeteren Voorbeeld chloordesinfectie Total reduction Current 2.1 Double dose 2.3 No events 2.5 Hydraulics 2.6 Hydr.+events 4.0

4.5 4

Log inactivation

5

3.5 3 2.5 2 1.5 1 0.5 0 27 Apr

07 May

17 May

27 May

06 Jun

16 Jun

Goal: 2.5 log to meet health target © Kiwa Water Research 2006

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Procesbewaking is essentieel! 6.5 Hours response time 5 4.5

Log inactivation

4 3.5

Monitored Monitored Running Monitored average Running Monitored average Correction Running average level Correction level Achievable average

3 2.5 2 1.5 1 0.5 0 27 Apr

07 May

17 May

27 May

06 Jun

16 Jun

Goal: achieve 2.5 log average inactivation over period © Kiwa Water Research 2006

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Procesbewaking: hoe vaak moet je meten? Risk from event < nominal risk (95% certainty)

nominal log reduction


Interval / year

1

1 week

2

1 day

3

3 hours

4

15 min

5

2 min 28

Verschillende landen, verschillende prioriteiten Westers ontwikkeld: verwaarloosbaar risico, hoe verifieer je dat? Beperkt ontwikkeld: hoe zorg je voor constante goede bedrijfsvoering? Primitief: hoe maak je mensen bewust van risico’s (latrines boven visvijver)

Source: F. Wieneke


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Microbiologische risico s van drinkwater

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