Woman drinking water

Health-based targets offer opportunity to improve insights on drinking water safety
C Owens, M Angles, M Crabtree
Publication Date (Web): 11 January 2017
DOI: https://doi.org/10.21139/wej.2017.005

It is intuitive to judge the safety of drinking water principally on an observed absence of contamination. 

This was the case at the birth of modern drinking water quality management: in 1855 John Snow (the founder of modern epidemiology) hesitated to link a substantial cholera outbreak to the Broad Street pump due to a lack of visible contamination in the water. To an extent this is also true in modern times, with water utilities typically offering insights into the microbial safety of drinking water based on an observed absence of specific pathogenic and indicator organisms. The context of water treatment and the ‘multiple-barrier’ approach is not necessarily (or usually) included in this discourse. Thus, an erroneous inference of operational response being made solely on the basis of lagging indicators may be made. Such a circumstance is not of benefit to the consumer or the utility.


Focussing consumer confidence reporting on critical control processes increases the importance of what is reported. Events known to be related to public health outcome are highlighted, and conversely, results not as strongly associated with public health outcome do not need to be included. Both cases are beneficial. Essentially, the connection between public health theory and drinking water supply practise can be reaffirmed. The introduction of a health-based target for the microbial safety of drinking water provides an opportunity to pursue such a shift in focus.

This was implemented in the case of Sydney Water in four steps. First, source risk and commensurate treatment requirements were identified using the two-tiered method established by Water Services Association of Australia. Second, treatment requirements were formalised under a Hazard Analysis and Critical Control Point (HACCP) approach. Third, HACCP performance data were assembled for internal reporting. Finally, organisational and stakeholder acceptance was established for these data and the processes they describe to form the basis of refocussed consumer confidence reporting. 

An online, daily report was established, demonstrating the performance of the filtration, primary and secondary chlorination, and fluoridation processes against national guidelines and the achievement of the 10-6 Disability-Adjusted Life Years per person per year health outcome target (Figure 1).

Excerpt of the Sydney Water daily drinking water quality report
Figure 1: Excerpt of the Sydney Water daily drinking water quality report demonstrating achievement of critical limits set under national guidelines, including those linked to health-based targets 

Establishing the report saw the need to create algorithms for treating and assembling operational data. Acceptance of the approach within the water utility was also important.

The implementation of the microbial HBT provides an opportunity to improve the importance of consumer confidence reporting. The associated measures may not be immediately intuitive, but by their nature are a powerfully transparent and accurate characterisation of whether and how the safety of drinking water is, in practice, assured. 

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