Review of Coliforms - National Health and Medical Research Council

6.2 WATER QUALITY RISK MANAGEMENT APPROACH
MICROBIAL INDICATORS OF DRINKING WATER QUALITY
Reliance on total coliforms for measurement of the microbial safety of a drinking water can
result in a false sense of assurance from negative results. In many instances, E. coli and total
coliforms are the sole indicators analysed to determine microbial water quality. The retrospective
study of waterborne disease outbreaks and advances in the understanding of the behaviour
of pathogens in water, has shown that continued reliance on bacterial indicators alone, and
assumptions surrounding the absence or presence of total coliforms does not ensure that
informed decisions are made regarding water quality.
A risk management approach to drinking water supply is being adopted across Australia to
increase confidence in the safety of drinking water and reduce reliance on end-point testing.
Several major Australian water suppliers have developed risk management plans that are a
holistic approach to water management. These plans systematically assess risks throughout
a drinking water supply, from the catchment and source water, through to the customer tap,
and identify the ways that these risks can be managed and methods to ensure that barriers
and control measures are working effectively. A risk management plan assesses the integrity
of the entire water supply system and is able to incorporate strategies to deal with day-to-day
management of water quality as well as upsets and failures.
The ongoing review of the Australian Drinking Water Guidelines (NHMRC-ARMCANZ, 1996),
is resulting in the development of a comprehensive drinking water quality management
framework. The framework supplements system management information currently included
in the Guidelines with principles from existing management systems such as the International
Organisation for Standardisation (ISO) series and the Hazard Analysis and Critical Control
Point (HACCP) system. HACCP is a risk prevention/risk management system that has been
used extensively in the food industry and is now being adopted for risk management of water
production and supply. The draft framework, which has been trialed in a number of water
supplies, will enable water managers to identify and rank risks within the water supply and
establish critical control points where these risks can be managed. The framework will focus
on total system management, measurement of barriers and verification using end-point testing.
Internationally, the World Health Organization (WHO, 1999) has developed a risk management
approach to water quality as a model for assessing the safety of recreational waters (the
Annapolis Protocol). This approach is being proposed as part of a harmonised framework
for managing risks from drinking water and food production. The WHO is further developing
this risk management approach in the current development of the Third Edition of the
Guidelines for Drinking-water Quality.
A risk management approach for drinking water includes (1) end-point monitoring to verify
that the water supplied to consumers was safe; and (2) operational monitoring to show
that treatment processes are functioning properly and that distribution system integrity is
maintained. End-point monitoring cannot be used as a system control measure, only as a final
verification step in a complete risk management plan. Operational monitoring is a means of
assessing system performance and results are used to modify system controls to ensure that
processes are working within specification. For this reason, on-line and continuous monitoring
for operational purposes is better able to support system management.
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