The National Health and Medical Research Council (NHMRC) is expanding microbial health based targets in a draft framework to be added to the Australian Drinking Water Guidelines (ADWG).
Microbial health-based targets (HBT) give a quantitative definition of drinking water safety using organisms that represent the major groups of pathogens – bacteria, viruses and protozoa.
“Currently, the only HBT for microbial safety in the ADWG is the absence of E. coli per 100 millilitres of water,” the NHMRC stated.
“However, E. coli is not an effective indicator organism for other bacteria in drinking water and cannot be used as an indicator for viral and protozoan pathogens.”
The draft framework is proposed for inclusion in Chapter Five (5.7) of the ADWG and defines safe, good quality drinking water and how it can be achieved.
“For smaller utilities, this could involve using default treatment processes based on categorising the type of water source,” the NHMRC stated.
“For more technically advanced utilities a more system-specific approach using water supply-specific monitoring data (where this exists) can be used.
“For utilities that do not meet the existing standards in the ADWG, the health-based target [HBT] framework describes a water safety continuum, where the utility can plan improvements to its operation in order to work towards the goal of safer water and best practice.”
The framework covers:
- applying HBT to drinking water supplies;
- determining minimum treatment requirements for drinking water supplies;
- specified treatment technologies for small or remote drinking water; and
- information on operational monitoring.
Appendices outline the specific technical details of applying HBT to water supplies, including how to calculate log reduction values, how to conduct source water assessments and an explanation of default log reduction value credits for common water treatment processes.
The HBT to be included in the guidelines is the same as that used in the World Health Organisation’s Guidelines for Drinking-water Quality.
The draft is open for public consultation, and submissions can be made online before November 4.