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Potential Health Risks Associated with the Use of Roof-Harvested Rainwater

Potential Health Risks Associated with the Use of Roof-Harvested Rainwater. CSIRO Land and Water. Simon Toze and Warish Ahmed. Urban Water Security Research Alliance. Health Risk Assessment of Local Source Waters Project. Roof-Harvested Rainwater System. Advantages of using RHRW.

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Potential Health Risks Associated with the Use of Roof-Harvested Rainwater

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  1. Potential Health Risks Associated with the Use of Roof-Harvested Rainwater CSIRO Land and Water Simon Toze and Warish Ahmed

  2. Urban Water Security Research Alliance Health Risk Assessment of Local Source Waters Project

  3. Roof-Harvested Rainwater System

  4. Advantages of using RHRW • In 2006, the Queensland State Government initiated “Home Water Wise Rebate Scheme” which provided subsidies to SEQ residents who used rainwater for non-potable domestic uses • More than 260,000 householders were granted subsidies by December 2008 when the scheme was concluded • Reducing the pressure of the mains water supply • Reducing storm water runoff that can often degrade creek ecosystem health • Providing an alternative water supply during times of water restrictions

  5. Reported Infection Cases Associated with the Consumption of Rainwater In contrast, the most credible epidemiological study reported that the consumption of rainwater did not increase the risk of gastroenteritis among young children in South Australia (Heyworth et al. 2006)

  6. Possible Sources of Faecal Pollution in Rainwater Tanks Birds Possums Lizards Frogs Snakes Fruit bats

  7. Research Aims • To quantify the numbers, frequency of occurrence and survival of faecal indicators and pathogens in a range of domestic rainwater tanks in SEQ • To apply health risk assessment to estimate the risk of infection from exposure to pathogens in rainwater tanks

  8. Selection and Survey of Rainwater Tanks • 80 rainwater tanks were selected representing 34 suburbs in Brisbane and Gold Coast Region • In addition, 24 samples were collected from household taps fed by rainwater tanks • Information on the presence of overhanging trees, faecal droppings on the roof, the gutter condition and uses of RHRW were also recorded

  9. Faecal Indicators and Pathogens Tested in this Study • Pathogens Faecal indicators E. coli Salmonella spp. Campylobacter spp. Enterococci Cryptosporidiumparvum Giardia lamblia

  10. Rainwater and Tap Water Sampling From the selected tanks (n = 80) and household taps (n = 24), 20 L of water samples collected for microbiological analysis

  11. Possum and Bird Faecal Sampling Peter the Possum Man Possum faecal samples were provided by Peter the Possum man Bird faecal samples were collected from the botanical gardens, a wildlife sanctuary and bins at a suburban shopping centre Bird faeces sampling

  12. Numbers of Faecal Indicators in Rainwater Tanks Above guideline value

  13. Numbers of Pathogens in Rainwater Tanks (n = 80) 5-110 cells/L 110-140 cysts/L 7,300 cells/L

  14. Occurrence of Pathogens in Rainwater Tanks and Connected Household taps Pathogen numbers detected in the tank were similar to out of the tap Testing of under bench filters found that bacteria were not removed

  15. Numbers of Pathogens in Possums and Birds Campylobacter spp. 24-61% (6.6 × 104 to 2 × 107) C. parvum5-13% (not quantifiable) G. lamblia13-30% (1.3 × 100 to1.6 × 103)

  16. Microbial Source Tracking in Rainwater Tanks % of E. coli isolates

  17. Pathogen Survival on Roofs

  18. Inactivation of Faecal Indicators on the Roof

  19. Inactivation of Faecal Indicators in the Gutter

  20. Inactivation of Faecal Indicators in Tank Water

  21. Inactivation kinetics of Microbes in Faecal Slurries and Tank Water

  22. Key Findings • 70% of the tanks exceeded the drinking water guideline value of 0 E. coli per 100 mL of water. • G. lamblia and Campylobacter spp. were present in a number of RHRW tanks and connected taps. • C. parvumcould not be detected in rainwater tanks and connected tap water samples. • Underbench filters are only useful against the larger protozoa

  23. Key findings • Possums and bird faecal samples were positive for G. lamblia and Campylobacter spp. • E. coli source tracking identified bird and possum faeces as the major source of pathogens and microbial indicators in tank water. • Faecal indicators inactivation: Sunlight> Shade> Rainwater tanks • RAIN WATER SHOULD BE TREATED BEFORE DRINKING

  24. www.urbanwateralliance.org.au Thank you • Simon Toze • CSIRO Land and Water • Ecosciences Precinct, Brisbane • Simon.Toze@csiro.au CSIRO Land and Water

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