D Health Major impact for small population – Environment Potentially lethal to local ecosystem; – predominantly but potential for off-site impacts E Severe Health impact for large population – Environment Potentially lethal to regional ecosystem or – threatened species, widespread on-site and off-site impacts Table Risk rating – Consequence Insignificant Moderate Severe Almost Medium High Very High Extreme Extreme Certain (5A) (5B) (5C) (5D) (5E) Likely Medium High High Very High Extreme (4A) (4B) (4C) (4D) (4E) Possible Low Medium High High Very High (3A) (3B) (3C) (3D) (3E) Likelihood Unlikely Low Medium Medium High Very High (2A) (2B) (2C) (2D) (2E) Rare Low Low Low Medium Very High (1A) (1B) (1C) (1D) (1E) Exposure risk levels When determining the of risk, the expected end use should be taken into account to determine the potential level of exposure that end users will have to the recycled water. Common end uses for recycled water are presented in Table 5. Table - Exposure Risk Levels, Classification of Recycled Water, and End Uses Risk Level Class End Uses Extreme A+ Multi-unit dwellings; internal reuse (toilet flushing and dedicated cold water taps for washing machines) or external surface irrigation Agricultural irrigation of food crops consumed raw or unprocessed (hydroponics, salad crops, etc) Very High A Urban surface irrigation with unrestricted access and application Fire fighting Fountains and features Dust suppression Cooling process water High B Urban irrigation with some restricted access and application Commercial food crops
D Health – Major impact for small population Environment – Potentially lethal to local ecosystem; predominantly but potential for off-site impacts E Severe Health – impact for large population Environment – Potentially lethal to regional ecosystem or threatened species, widespread on-site and off-site impacts Table – Risk rating Consequence Insignificant Moderate Severe Likelihood Almost Certain Medium (5A) High (5B) Very High (5C) Extreme (5D) Extreme (5E) Likely Medium (4A) High (4B) High (4C) Very High (4D) Extreme (4E) Possible Low (3A) Medium (3B) High (3C) High (3D) Very High (3E) Unlikely Low (2A) Medium (2B) Medium (2C) High (2D) Very High (2E) Rare Low (1A) Low (1B) Low (1C) Medium (1D) Very High (1E) Exposure risk levels When determining the of risk, the expected end use should be taken into account to determine the potential level of exposure that end users will have to the recycled water. Common end uses for recycled water are presented in Table 5. Table - Exposure Risk Levels, Classification of Recycled Water, and End Uses Risk Level Class End Uses Extreme A+ Multi-unit dwellings; internal reuse (toilet flushing and dedicated cold water taps for washing machines) or external surface irrigation Agricultural irrigation of food crops consumed raw or unprocessed (hydroponics, salad crops, etc) Very High A Urban surface irrigation with unrestricted access and application Fire fighting Fountains and features Dust suppression Cooling process water High B Urban irrigation with some restricted access and application Commercial food crops
draft-guidelines-wastewater-works-design-approval-for-recycled-water-systems.docx