Sydney Water Corporation (Sydney Water) is required to report to NSW Health any event or information within its water supply system that may adversely affect public health.
The NSW Chief Health Officer has the responsibility under the Public Health Act 2010 to issue advice to the public regarding measures available to minimise risk from disease, including water-borne disease. The Chief Health Officer may from time to time decide, in relation to any supplier of drinking water:
This responsibility requires the Chief Health Officer to rapidly assess any report of problems related to drinking water and ensure action is promptly taken to address the problem. Problems related to drinking water may include:
A failure of water treatment or primary disinfection will trigger an investigation by the Sydney Water.
In the case of treatment failure, the Chief Health Officer will consider the need for a boil water alert where treated water turbidity did not meet target and water can not be diverted before entering the water supply system, and:
Examples of conditions that would be considered to increase catchment risk rating include (but are not limited to):
In the case of disinfection failure, the Chief Health Officer will consider the need for a boil water alert where an adequate disinfection residual can not be maintained at the last point of primary disinfection before the consumer.
The critical control point limits that indicate a failure of the treatment and disinfection systems for Sydney Water surface supplies have been determined in consultation with NSW Health and are summarised in the Response Protocol Flowchart.
Where testing of treated water for Giardia cysts or Cryptosporidium oocysts has been performed, the detection of parasites at any level will trigger an investigation by Sydney Water for potential failures of water treatment. However, the detection of Cryptosporidium in water does not confirm whether the organism is viable or a risk of human infection. While there are more than 20 recognised species of Cryptosporidium, almost all identified cases of waterborne disease in humans have been caused by only two species. Sydney Water will inform NSW Health and WaterNSW of positive Giardia or Cryptosporidium results within one hour of receiving them. There is separate response protocol following the detection of E. coli.
The investigation triggered by a positive result should include (but not be limited to) an assessment of:
If Cryptosporidium is detected, immediate re-sampling should occur as it is resistant to chlorine disinfection. If Giardia is detected (but not Cryptosporidium), NSW Health and Sydney Water will review the conditions of disinfection in order to determine the need for resampling.
The Chief Health Officer will consider the need for a boil water alert or other public health responses (including the convening of the NSW Health Water Expert Panel) where Cryptosporidium or Giardia is detected and:
The NSW Health Water Expert Panel has a permanent ongoing role as a Standing Committee. The Chief Health Officer may call on the advice of the NSW Health Water Expert Panel when making a decision on the most appropriate health response in situations including the following:
If an outbreak of illness occurs in the population due to infection with Giardia or Cryptosporidium, NSW Health will investigate and manage the incident following its standard procedures. If the Chief Health Officer has reason to suspect that the cause of the outbreak may be related to the consumption of drinking water, they may seek advice from the NSW Health Water Expert Panel.
When deciding whether to issue a boil water alert, the Chief Health Officer will consider:
Protection of public health is a priority. The Chief Health Officer must also consider possible adverse consequences of a boil water alert, such as scalds. The Chief Health Officer may decide not to issue a boil water alert if there is no clear public health benefit. For example, where results of a routine test are positive but subsequent tests are clear, and continued exposure to contaminants is unlikely. However, it may be useful to increase surveillance for illness and to continue to monitor the situation closely.
Other responses may include:
The NSW Chief Health Officer has the responsibility to lift boil water alerts. The Chief Health Officer will take into account the following factors:
The Response Protocol Flowchart summarises the critical control point limits for treatment and primary disinfection processes for the Sydney Water supply.