Gertjan Medema KWR Watercycle Research Institute NL. Delft University of Technology NL. WHO Collaborating Centre for. Water Quality & Health

Transcription

1 EC/JRC workshop water reuse 25/26 June Brussels 1 Risk assessment approach for water reuse Gertjan Medema KWR Watercycle Research Institute NL Water Quality & Health Delft University of Technology NL WHO Collaborating Centre for

2 EC/JRC workshop water reuse 25/26 June Brussels 2 Risk assessment & management approach for water reuse Gertjan Medema KWR Watercycle Research Institute NL Delft University of Technology NL

3 EC/JRC workshop water reuse 25/26 June Brussels 3 My main perspective Human health microbial safety CAMPYLOBACTER ENTEROVIRUS CRYPTOSPORIDIUM

4 Bridging science to practice Water safety assessment based on testing of faecal indicator bacteria 4 Too little, too late E.COLI TESTING Outbreaks/cases while (drinking) water is in compliance with E. coli standards USA fresh produce Top 1 in number of illnesses (22% of 9,600,000) Top 2 in number of hospitalizations (14% of 57,000) Top 6 in number of deaths (6% of 1,450) More resistant/persistent pathogens Enteroviruses, Rotaviruses, Adenoviruses, Hepatitis A & E viruses, Noroviruses, Cryptosporidium, Giardia, Cyclospora, Test results in hrs Testing frequency too low

5 Bridging science to practice Water safety assessment based on testing of faecal indicator bacteria Too little, too late 2 E.COLI TESTING 5 End-product testing of FIB does not create understanding of hazards, hazardous events and control measures in the water supply system Retrospective check, not proactive demonstration of safety Safety is in system design, operation, maintenance

6 Bridging science to practice Water safety assessment based on testing of faecal indicator bacteria Too little, too late 3 E.COLI TESTING 6 Developments in society Due diligence expected Other sectors (food safety) have moved to preventitive farm-tofork risk management Aging / lowering immunity Citizens expect low / no (unvoluntary) risk Developments in science Sensor technology for intake / process control QMRA: evidence-based risk management New microbial methods ((q)pcr): pathogen testing

7 EC/JRC workshop water reuse 25/26 June Brussels 7 WHO: new paradigm for water safety Focus on human health, microbial hazards From water quality testing to system assessment Water Safety Plans Sanitation Safety Plans SAFE WATER FRAMEWORK (WHO, 2001)

8 EC/JRC workshop water reuse 25/26 June Brussels 8 WHO water guidelines Main focus: human health microbial hazards From water quality testing to system safety assessment

9 EC/JRC workshop water reuse 25/26 June Brussels 9 System safety assessment Pathogen source Barrier efficacy Exposure to water

10 QMRA for water reuse in agriculture Raw food crops

11 Bridging science to practice 11 QMRA: Exposure assessment Data on Norovirus in sewage Site data collected by University of Barcelona Data on virus removal/inactivation by activated sludge, UV/Cl 2 Data on virus transmission from wastewater to lettuce Data on virus survival (and internalization) on lettuce in field and during transport Data on virus removal by washing Literature/national statistics data collected Data on lettuce consumption (regional statistics)

12 Bridging science to practice 12 Results: Norovirus infection risk vs treatment efficacy Without With internalization internalization Current virus Desirable virus removal removal Additional treatment? Improved design/operation

13 EC/JRC workshop water reuse 25/26 June Brussels 13 Australian Water Recycling guidelines Best practice example of translation to system safety assessment Wide range of reuse applications Fit-for-purpose, based on exposure Not only wastewater treatment but all barriers in the exposure chain (irrigation type, withholding times, public access, ) Allows flexibility in how to meet the objectives Compatible with food safety guidelines/regulations WHO risk assessment/risk management approach translated to Australia Risk assessment & DALY s translated to system performance objectives: science at the back, practical feasibility at the front Water quality monitoring to demonstrate system meets performance objectives: validation, operation, verification

14 EC/JRC workshop water reuse 25/26 June Brussels 14 Applications Sewage/greywater Water treatment options, storage, distribution Intentional/unintentional exposure Residential uses Municipal uses Agricultural uses Fire control use Environmental uses Human health Environmental/farming health

15 EC/JRC workshop water reuse 25/26 June Brussels 15 Science at the back (QMRA).. PATHOGENS IN SOURCE WATER EXPOSURE VIA DIFFERENT USES DOSE RESPONSE/DALYS Select reference pathogens: virus, bacterium, parasite on the basis of health burden and waterborne transmission Food crop consumption National data on concentration in (commercial) wastewater Campylobacter = 7000 org.l 1 Adenovirus = 8000 org.l 1 Cryptosporidium = 2000 oocysts.l 1 Route of Volume Frequency/ Activity exposure (ml) person/year Comments Garden irrigation Ingestion of sprays Garden watering estimated to typically occur ever second day during dry months (half year). Exposu aerosols occurs during watering. Garden irrigation Routine ingestion 1 90 Routine exposure results from indirect ingestion v contact with plants, lawns, etc. Accidental Infrequent event. ingestion Municipal irrigation Ingestion 1 50 Frequencies moderate as most people use municip areas sparingly (estimate 1/2 3 weeks). People are unlikely to be directly exposed to large amounts of spray and therefore exposure is from indirect ingestion via contact with lawns etc. Like be higher when used to irrigate facilities such as s grounds and golf courses (estimate 1/week). Food crop consumption (home grown) Ingestion 5 (lettuce) 7 1 (other raw 50 produce) 100 g of lettuce leaves hold 10.8 ml water and cucumbers 0.4 ml at worst case (immediately po watering). a A serve of lettuce (40 g) might hold 5 of recycled water and other produce might hold u 1 ml per serve. Calculated frequencies are based on ABS data. b Food crop Ingestion 5 (lettuce) g of lettuce leaves hold 10.8 ml water and 140 consumption cucumbers 0.4 ml at worst case (immediately po (commercial) watering). a A serve of lettuce (40 g) might hold 5 1 (other raw 140 of recycled water and other produce might hold u produce) 1 ml ml per serve. per serve. Calculated frequencies are based on ABS data. c Toilet flushing Ingestion of sprays Frequency based on 3 uses of home toilet per day Aerosol volumes are less than those produced by garden irrigation. Washing machine use Ingestion of sprays Assumes one member of household exposed. Calculated frequency based on ABS data. d Aeroso volumes are less than those produced by garden irrigation (machines usually closed during operati Firefighting Ingestion of water and sprays Median ingestion for firefighters estimated at 20 m per fire with a maximum number of fires fought within area served by recycled water of 50 per ye Cross-connection of Ingestion 1000/day 1/1000 Total consumption is assumed to be 2 litres per da dual-reticulation systems with drinking water mains houses which 1 litre is consumed cold. g Affected individu may consume water 365 days per year. A conserv estimate of 1/1000 houses has been considered. Organism type Distribution Model Parameters Enteric virus (rotavirus) Beta Poisson Pinf = 1-(1+d/ß) α α = ß = Bacterium (Campylobacter jejuni) Beta Poisson α = ß = 7.58 Protozoan (Cryptosporidium parvum) Exponential Pinf = 1 exp( rd) r = Ingestion 5 (lettuce) 1 (other raw g of lettuce leaves hold 10.8 ml water and cucumbers 0.4 ml at worst case (immediately po watering). a A serve of lettuce (40 g) might hold 5 of recycled water and other produce might hold u produce) Calculated frequencies are based on ABS data. c and r are parameters describing probability of infection; d = dose; ß = median infective dose (N50 ) (21/α 1); Pinf = probability of infection Model parameters are as described in Table 9.15 from Haas et al (1999)), except for Cryptosporidium, where the data of Messner et al (2001) have been used

16 10 juni Symposium de Watergroep / Brussel 16 More science at the back. Barrier efficacy Wastewater Treatment Escherichia coli Bacterial pathogens (including Campylobacter) Viruses (including adenoviruses, rotaviruses and enteroviruses) Indicative log reductions a Treatment Primary treatment N/A Secondary treatment Dual media filtration with coagulation Phage Membrane filtration 3.5 > > >6.0 3 >6.0 >6.0 >6.0 >6.0 >6.0 Reverse osmosis >6.0 >6.0 >6.0 >6.0 >6.0 >6.0 >6.0 >6.0 Lagoon storage N/A 1.5 >3.0 Chlorination Ozonation N/A N/A N/A UV light 2.0 > >4.0 >1.0 adenovirus >3.0 enterovirus, hepatitis A >3.0 >3.0 N/A N/A Wetlands surface flow N/A Wetlands subsurface flow N/A N/A Giardia Cryptosporidium Clostridium perfringens Helminths

17 10 juni Symposium de Watergroep / Brussel 17 More science at the back. Barrier efficacy Farming practices Control measure Cooking or processing of produce (e.g. cereal, wine grapes) Removal of skins from produce before consumption Drip irrigation of crops Drip irrigation of crops with limited to no ground contact (e.g. tomatoes, capsicums) Drip irrigation of raised crops with no ground contact (e.g. apples, apricots, grapes) Subsurface irrigation of above ground crops Withholding periods produce (decay rate) Withholding periods for irrigation of parks/sports grounds (1 4 hours) Spray drift control (microsprinklers, anemometer systems, inward-throwing sprinklers, etc) Drip irrigation of plants/shrubs Subsurface irrigation of plants/shrubs or grassed areas No public access during irrigation No public access during irrigation and limited contact after (non-grassed areas) (e.g. food crop irrigation) Buffer zones (25-30 m) Reduction in exposure to pathogens 5 6 log 2log 2log 3 log 5 log 4log 0.5 log/day a 1 log 1 log 4log 5 6 logs 2log 3 log 1log

18 EC/JRC workshop water reuse 25/26 June Brussels 18. practice at the front Commercial non-food crops: secondary + farm Secondary treatment Validated (based on fecal indicators) Operational monitoring Flow rate Sludge blanket depth Farming practice Non-food crops (wood, energy, flowers, ) irrigation No access during irrigation Buffer zones >50m Campylobacter: Adenovirus: Cryptosporidium: 2 log 1 log 1 log Campylobacter: Adenovirus: Cryptosporidium: 5 log 5 log 5 log Verification monitoring: E. coli <10000/100mL

19 EC/JRC workshop water reuse 25/26 June Brussels 19. practice at the front Commercial food crops: secondary + farm Secondary treatment Farming practice Validated (based on fecal indicators) Operational monitoring Flow rate Sludge blanket depth Food crops heavily processed (grapes, cereals) or cooked (potatoes etc.) irrigation No access during irrigation Buffer zones >50m Campylobacter: 5 log Campylobacter: 2 log Adenovirus: 5 log Adenovirus: 1 log Cryptosporidium: 5 log Cryptosporidium: 1 log Verification monitoring: E. coli <1000/100mL

20 EC/JRC workshop water reuse 25/26 June Brussels 20. practice at the front Commercial food crops: secondary + disinfection + farm Secondary treatment Validated (based on fecal indicators) Operational monitoring Flow rate Sludge blanket depth UV/HOCl Validated UV reactors Operational monitoring UV transmittance UV irradiation Flow Farming practice Food crops with limited processing Drip irrigation Withholding time 2 days Campylobacter: Adenovirus: Cryptosporidium: 2 log 1 log 1 log Campylobacter: Adenovirus: Cryptosporidium: 4 log 1 log 3 log Campylobacter: Adenovirus: Cryptosporidium: 3 log 3 log 3 log Verification monitoring: E. coli <100/100mL

21 EC/JRC workshop water reuse 25/26 June Brussels 21 Improving on best practice Based on WHO guidelines Safety based on understanding and control of hazards and water systems = Water Safety Plan / Sanitation Safety Plan approach Science-based, but practice in forefront: translate QMRA, DALYs etc to practical requirements for design/operations/maintenance Operational monitoring in forefront, health-related water quality monitoring (E. coli/phages/ ) is only to verify from time-to-time that system does what it is designed and operated for Validation of system performance should not be asked from operator, but be based on state-of-the-art knowledge