Health Risk Assessment of Local Source Waters
Urban rainwater and stormwater are some of the most likely "new" sources of water in South East Queensland. Such water has high potential to replace significant volumes of grid water for a range of end uses, from irrigation and toilet flushing through to potable uses such as cooking and drinking. However, due to current uncertainty of the quality of these water sources there are restrictions on many uses within households. Depending on the water use, and water treatment processes (eg, disinfection), an acute risk relates to the potential presence of human pathogens such as protozoans, viruses and bacteria. Similarly, a chronic risk relates to trace organics and heavy metals.
Information on the range and prevalence of pathogens and contaminants is necessary to guide harvested rain and stormwater to appropriate end uses, and maximise grid water savings. Knowledge of pathogens is limited, especially for stormwater. For example, there is no common knowledge of the types and sources of pathogens. Accurate quantitative risk models have not yet been developed due to insufficient information.
This project aimed to provide an accurate assessment of the risks from pathogens in stormwater and rainwater tanks. This assessment was used to test the actual potential health risks for a number of potential exposure pathways via a Quantitative Microbial Risk Assessment (QMRA). Research questions addressed included:
- What are the most common pathogens in stormwater and rainwater systems?
- What are the major influences impacting pathogens and their survival?
- What mechanisms effectively impact pathogen survival?
- What are appropriate indicators of increased pathogen or chemical risk?
- What are the actual risks of exposure and what management is needed to negate those risks (eg, rainwater tank maintenance)?
- How does chemical and micro-biological quality vary (eg, in greenfield and brownfield sites), along with the subsequent health risk for a range of end uses?
- How cost-effective is rainwater and stormwater harvesting, when risks are managed to appropriate levels?
Key Publications and Outputs
- Technical Report 77 and 102
- Conference papers listed on the Alliance website
- Proceedings of the Alliance Science Forums
Sidu, J.P.S., Hodgers, L., Ahmed, W., Chong, M.N. and Toze, S. (2012) Prevalence of human pathogens and indicators in stormwater runoff in Brisbane, Australia. Water Research 46 (20): 6652-6660.
Ahmed, W., Gardner T. and Toze S. (2011). Microbiological Quality of Roof-Harvested Rainwater and Health Risks: A Review. Journal of Environmental Quality. 40: 13-21. doi: 10.2134/jeq2010.0345
Ahmed, W., Hodgers, L., Masters, N., Sidhu, J.P.S., Katouli, M. and Toze, S. (2011) Occurrence of Intestinal and Extraintestinal Virulence Genes in Escherichia coli Isolates from Rainwater Tanks in Southeast Queensland, Australia. Applied and Environmental Microbiology. 77 (20): 7394-7400.
Sampling has been conducted and review of chemicals and pathogens in stormwater and rainwater the resulting health assessment has been completed. Separate review of predictive models and treatment technologies is complete.
The results of this project will be used for the formulation of transparent policies and guidelines for the treatment and use of rainwater and stormwater. This will help guide the levels of treatment required for fit-for-purpose use. If necessary, it will also inform restrictions for some uses and management requirements for storage tanks and distribution systems.
Dr Simon Toze, CSIRO
Ph: +61-7-3833 5572