Review of Coliforms - National Health and Medical Research Council

7. CONCLUSIONS
MICROBIAL INDICATORS OF DRINKING WATER QUALITY
Water suppliers have been aware of the role of water in disease transmission for more than
150 years, during which time the primary focus of managing drinking water has been the
protection of public health. The fundamental issues associated with public health impacts
and the need for safe drinking water are currently well understood.
The Australian and international water industry is making a positive move towards
understanding and managing risks to public health from drinking water. This has been
driven by advances in methods for detecting pathogens, epidemiological studies to measure
background levels of waterborne disease, and a realisation that over reliance on treatment
processes to protect public health is not a sustainable management approach.
Detailed assessment of the factors that influence water quality necessarily includes a review
of the way in which the microbial safety of water delivered is measured. The current focus
on the absence of total coliforms and E. coli to ensure water quality has been shown to be
flawed and the water industry and regulators internationally are evaluating alternative ways
to protect public health and the usefulness of these indicators.
The collection of information on water quality is costly, therefore data needs to be
unambiguous, and able to assist risk management decisions. The presence of E. coli in
treated water is still considered to indicate faecal pollution and remains a key verification
tool. The uncertainty surrounding the relevance of other coliforms in drinking water means
that their value as an indicator is limited. A set of indicators, used in conjunction with
total-system risk management, is required that increases confidence in the safety of water
delivered to consumers.
The move by the EU to downgrade total coliforms and include mandatory measurement
of enterococci as well as E. coli is one that recognises the worth of using specific indicators
of faecal pollution, and assigns a minor role to total coliforms.
The limitation of total coliforms in Australia has been reaffirmed in the ongoing review of
the Australian Drinking Water Guidelines (NHMRC-ARMCANZ, 1996). The revised Fact Sheets
for thermotolerant coliforms/E. coli and total coliforms acknowledge that coliforms can be
of environmental origin and that their presence in drinking water is not necessarily indicative
of a health risk.
The importance of risk management is also addressed in the ongoing review of the Australian
Drinking Water Guidelines (NHMRC-ARMCANZ, 1996) with the development and trialing
of a framework for the risk management of drinking water systems. The development of
a set of criteria to verify that risk management plans are effective is a necessary part of this
approach to water quality. In the long-term review of appropriate water quality monitoring,
it is envisaged that a matrix approach will be adopted, with less significance on single
parameters such as total coliforms.
The next step in the current direction of water quality management and compliance monitoring
for Australia is to reduce reliance on total coliforms and increase emphasis on implementation
of risk management systems, measurement of specific faecal indicators, and assessment of the
effectiveness of source water protection, treatment and disinfection barriers.
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