Safe distribution of drinking water without disinfectant residual...(Asp. fumigatus, Fus....
Transcript of Safe distribution of drinking water without disinfectant residual...(Asp. fumigatus, Fus....
Safe distribution of drinking water
without disinfectant residual
Gertjan Medema
Chief science officer KWR / Chair on Water and Health Delft University of Technology
The Netherlands
16 milion people on
40.844 kms
The road to distribution of drinking water
without disinfectant residual
The road to distribution of drinking water
without disinfectant residual
1970: chlorination in water treatment of surface water supplies (breakpoint chlorination) and in distribution network
1974: Dr. J. Rook of Rotterdam Water Supply discovered THM formation by chlorination in surface water treatment
1975 - 1980’s: research into THM formation, precursor removal and toxicity and significant reduction of chlorine dose used for breakpoint chlorination, transport chlorination, lower doses in summer
The road to distribution of drinking water
without disinfectant residual 2
1980’s: research showed chlorination in distribution
network has significant contribution to THM
formation
1980’s: water utilities significantly reduced chlorine
dose in network. No residual in all the network, only
network close to treatment works.
1980’s: follow-up monitoring of reduced chlorination
in network: less THMs, coliforms and HPC no
increase
The road to distribution of drinking water
without disinfectant residual
1983: Amsterdam Water Supply experimented with stepwise
reduction of post-treatment chlorine dose to zero and monitored
water quality
Even though DBP concentrations below 10-6 lifetime risk, post-
chlorination was stopped, in Amsterdam and other surface water
supplies.
+ HOCl -HOCl
THMs 12-22 ug/l 0 ug/L
Ames response + -
Ecoli/enterococci 0/100 ml 0/100 ml
HPC 2-5/ml 2-5/ml
AOC - 40%
Chlorination in surface water treatment
replaced by other disinfection processes
Amsterdam (Waternet): ozone + slow
sand filtration
Rotterdam (Evides): UV (2005)
South-west Netherlands (Evides): ozone
North-west Netherlands (PWN): UV/H2O2
(2004)
Since 2005 chlorination only used in
emergency contaminations Evides
205 27mve 12
Noblesse oblige!
Maintaining and demonstrating safety
of distributing drinking water without
disinfectant residual
Part 1: barriers against ingress of
microbial contaminants
Barriers against contamination of the
distribution system
Hygiene code - Distance from source
- Construction
- Maintenance/repairs
Structural integrity - Material approval codes
- Construction codes - Backsiphonage protection
Hydraulic integrity - Pressure
- Continuity of supply
- Redundancy
Distribution system
Is better sentinel in
unchlorinated systems
Microbial monitoring
Distribution networks in the Netherlands
Geographic situation
Flat, little seismic activity
Clay, loam, sand, peat soils
120.000 km
50% PVC
30% AC
10% CI
10% other
Very low leakage (<3%)
Water demand 125 L pppd
Leakage rates (VEWIN, 2005, DVGW, 2008)
Are the barriers against ingress
working and effective?
1. Health data
2. Water quality data
3. Utility performance data
Are the barriers against ingress
working and effective?
1. Health data
Waterborne outbreaks
2. Water quality data
3. Utility performance data
Outbreaks via community water supplies
USA 1971 – 2002: 671 outbreaks (19% via distribution and increasing)
= 0.08 per million people per year
Europe 1990-2004: 86 outbreaks (33% via distribution):
= 0.001 per million people per year
NL 1981 – 2012: 2 outbreaks (100% via distribution)
= 0.0004 per million people per year
No evidence that absence of residual in water would increase risk of
outbreaks
Are the barriers against ingress
working and effective?
1. Health data
Waterborne outbreaks: no evidence that absence of residual in water
would increase risk of outbreaks
2. Water quality data
E. coli
3. Utility performance data
Finished water Distribution system
France 369 (54,560) 0.7% 903 (144,138) 0.6%
Netherlands 17 (39,545) 0.04% 99 (107,593) 0.09%
Germany 1 (20,737) 0.005% 15 (12,530) 0.1%
Total 387 (114,842) 0,34% 1,017 (264,261) 0,38%
Country
Samples with positive E. coli detection
Number (total number) %
+HOCl
-HOCl
Statutory E. coli monitoring in tap water
What does it tell us? (Hambsch et al.,2007; van Lieverloo et al, 2006)
France, Germany, Netherlands( 45 million Europeans)
2100 distribution areas
3 years
Repeat samples (NL data): 2.3% E. coli
HOCL certainly not better, but small systems influence picture
Are the barriers against ingress
working and effective?
1. Health data
Waterborne outbreaks: no evidence that absence of residual in water
would increase risk of outbreaks
2. Water quality data
E. coli: systems without residual less contamination than with residual
3. Utility performance data
Are the barriers against ingress
working and effective?
1. Health data
Waterborne outbreaks: no evidence that absence of residual in water
would increase risk of outbreaks
2. Water quality data
E. coli: systems without residual less contamination than with residual
Quantitative Microbial Risk Assessment
3. Utility performance data
QMRA of fecal contamination incidents
(van Lieverloo et al., 2007)
Incident is repeated E. coli detection
1994 – 2003
Netherlands
7 water utilities
50 incidents
5 / year
185000 consumers affected
Probability of being affected by incident:
1.7 x 10-3
Incidents: how long do they last?
(van Lieverloo et al., 2007)
Incidents: how contaminated is the water?
(van Lieverloo et al., 2007)
Incidents: what is the health risk?
(van Lieverloo et al., 2007)
Of incidents we know:
• Duration (reasonably well, mostly not from start)
• Severity ([E. coli]) (reasonably well, mostly not from start)
Severity ([pathogen]) (assumption based on ratio to E. coli)
• # affected consumers (estimate)
In general we know:
• Volume of (cold) tap water that is consumed
• Dose-effect relations pathogens
Calculate probability of infection
Translation to health risk
(van Lieverloo et al., 2007)
Probability of infection of incidents >> 10-4
Pathogen data missing
Are the barriers against ingress
working and effective?
1. Health data
Waterborne outbreaks: no evidence that absence of residual in water
would increase risk of outbreaks
2. Water quality data
E. coli: systems without residual less contamination than with residual
Quantitative Microbial Risk Assessment: incident risk is high
3. Utility performance data
Are the barriers against ingress
working and effective?
1. Health data
Waterborne outbreaks: no evidence that absence of residual in water would increase risk of outbreaks
2. Water quality data
E. coli: systems without residual less contamination than with residual
Quantitative Microbial Risk Assessment: incident risk is high
3. Utility performance data
Interruption of supply
Water pressure
Operational data distribution networks
(based on Ofwat, 2008)
Main
bursts per
1000 km
Leakage
m3/km/d
Unplanned
interruptions
per 1000
properties
Properties
at risk of
low
pressure
England/Wales 187 10.1 23 0.02%
Scotland 166 21.3 34 0.31%
Canada 66 11.9 21
Australia 4.4 50
Portugal 67 7.0 0.4 (>12 hr)
USA 629*
3
Netherlands 70**
1.6 ***
*LeChevallier et al., 2011 indicate an industry average of 23-27 breaks per 100 miles, or approx. 150 per 1000 km
**All failures, not only main bursts
***Unplanned interruptions in the Netherlands are, on average, 7.5 min per property per year
Pressure logging:
low pressure events, no negative pressure events
00:00 06:00 12:00 18:00 00:00 06:00 12:00 18:00 00:000
1
2
3
4
tijd (26 - 27 aug 2008)
dru
k (
bar
)
NH Hotel
De Ruyterstraat
Burg. Fennemaplein
08:50 08:55 09:00 09:05 09:100
1
2
3
4
tijd (26 aug 2008)
dru
k (
bar
)
NH Hotel
De Ruyterstraat
Burg. Fennemaplein
Are the barriers against ingress
working and effective?
1. Health data
Waterborne outbreaks: no evidence that absence of residual in water would increase risk of outbreaks
2. Water quality data
E. coli: systems without residual less contamination than with residual
Quantitative Microbial Risk Assessment: incident risk is high
3. Utility performance data
Interruption of supply: low leakage and interruption levels
Water pressure: limited evidence that no negative pressure transients
Part 2: barriers against regrowth of microorganisms
Nutrient limitation = regrowth control
Van der Kooij, van Lieverloo, van der Wielen (KWR)
Barriers against regrowth
R & D: biostability toolbox
Biostable water
- Continuous research & toolbox biostability of water in use since 1980’s
- Industry guideline values for biostable water (AOC, BFP)
Dr. Dick van der Kooij AOC (1980’s) Biofilm monitor
(1990’s)
Boiler
Biofilm monitor
(2000’s)
Barriers against regrowth
Biostable water
1 5 10 15 20 25 30 35 40 45 50 Treatment plant
0
25
50
75 Surface water treatment
Groundwater treatment
Barriers against regrowth
Biostable water
- Phreatic groundwater & bank filtrate: already very biostable
- Anaerobic, deep groundwater: optimise biostability by
optimising/additional treatment (methane removal, organic
carbon removal)
- Extensive treatment of surface water to remove nutrients
- infiltation in sandy soil
- ozone + biological GAC filtration
- slow sand filtration
Barriers against regrowth
Biostable materials
Biostable materials
- Materials testing protocols: low regrowth potential
- Pipes, connections, valves etc.
Biofilm Formation Potential of materials
1,2: Glass; nrs
3,4: Stainless Steel
5-9: hard PVC
10: polypropylene
11-15: high density PE (PE80)
16-20: low density PE (PE40)
21: PE80.
Current R&D
Opportunistic pathogens (molecular methods)
Step 1: priority setting Organism Cases Epidemiology Occurrence Priority
L. pneumophila +++ ++ + Very high
NTM ++ ++ + High
P. aeruginosa + + + High
Pathogenic fungi + ++ + High
S. maltophilia +/- + + Moderate
Acanthamoeba spp. +/- ++ - Moderate
B. cepacia complex +/- + Unknown Low
A. baumannii complex +/- - Unknown Low
Aeromonas spp. +/- - + Low
Y. enterocolitica ++ - Unknown Low
Afipia spp. - - Unknown Low
Bosea spp. - - Unknown Low
B. pseudomallei - ++ Unknown Low
S. negevensis - +/- Unknown Low
E. meningoseptica - +/- Unknown Low
Methylobacteria - - Unknown Low
N. fowleri - +/- Unknown Low
Current R&D
Opportunistic pathogens (molecular methods)
Step 2: development of molecular methods
• Existing: Legionella & host protozoa
• New: non tuberculous mycobacteria, Pseudomonas aeruginosa, pathogenic fungi (Asp. fumigatus, Fus. oxysporum), Stenotrophomonas maltophilia
qPCR for detection:
• conditions that support/limit growth of opportunistic pathogens
Genotyping:
• comparing strains from water & patient
Overview
Providing safe, sustainable and environment-friendly drinking water
- No chlorine residual: research program
- Protection against contamination
- Low leakage rates
- Low levels of interrupted supply, no neg. pressure
- Low levels of outbreaks and contamination incidents
- Protection against regrowth
- Biostable water
- Biostable materials
- Demonstrating due diligence
- Water quality monitoring, microbial risk assessment
- Operational data collection
- BTO research program
Acknowledgements
KWR
Dick van der Kooij, Hein van Lieverloo, Patrick Smeets, Mirjam Blokker, Edwin Kardinaal, Jan Vreeburg, Harm Veenendaal, Anke Brouwer, LMB technicians
Water utilities
Vitens, Brabant Water, Evides, PWN, Dunea, Waternet, WML, Waterbedrijf Groningen, Waterleidingmaatschappij Drente, Oasen.
Waterlaboratories
The Microrisk partners, particularly Beate Hambsch, Emmanuel Soyeux, Jean Francois Loret, Paula Agutter
BTO: Joint Research Program of Netherlands Water Supply, particularly the microbiology program committee
European Commission FP6