What are Health Based Targets (HBT)?
Health Based Targets (HBTs) are an Australian application of a process recognised around the world by organisations such as the World Health Organisation (WHO) for quantitatively assessing microbiological risks associated with source waters used for drinking water supply.
The numerical output of a quantitative microbial risk assessment (QMRA) addresses the microbial drinking water risk management question in greater detail and allows for a more precise comparison between risk management options compared with alternative qualitative or semi-quantitative approaches.
The HBT Assessment process uses QMRA which is consistent with the Australian Drinking Water Guidelines (ADWG) Framework and is to be included in the next version of the ADWG which is currently being developed. This process includes guidance on estimating the quantitative, residual risk through a series of guidelines that are based on internationally accepted standards and which deliver consistency across Australia.
Why Complete a HBT Assessment?
Completing a HBT Assessment is a means of quantitatively demonstrating that the microbial risks to your drinking water supply due to quality of the raw source waters are being adequately addressed by any treatment system you may have. The aim of the QMRA is to demonstrate that the residual risk has been reduced to <1 micro Disability Adjusted Life Year (1 µDALY) the metric set by the World Health Organisation (WHO) as the tolerable measure for a population impact to a health problem.
As this HBT Assessment process is being included in the next revision of the ADWG, it is expected that completion of HBT Assessments will become a requirement from regulators in the near future. Therefore, it is best to be on the front foot, by understanding any risks in your systems that may need to be addressed, so that you can at least be working towards achieving the goal of <1 µDALY of residual risk in your drinking water supply.
How is a HBT Assessment Completed?
A HBT Assessment involves completing a Source Water Assessment which includes an examination of potential sources of microbial contamination within the water supply catchment area and the potential magnitude of that contamination. An assessment of the E. coli monitoring data from the inlet to the water treatment system is then used to ensure the source water is assigned to an appropriate category ranging from ‘well protected source’ to ‘unprotected’. These categories have assigned performance targets which are expressed in terms of log reduction targets which need to be met by the treatment processes downstream.
The Water Treatment Assessment is then undertaken to determine what pathogen log reductions are being achieved by the treatment processes. The results of the Source Water Assessment and the Water Treatment Assessment are then compared to identify any gaps in pathogen log reductions and develop a plan for addressing any risk posed by those gaps.
How Ecosafe Can Help
Our Team of specialists are able to assist you with completing your system specific HBT Assessments for both new and existing drinking / potable water systems. We look forward to assisting you in completing a HBT Assessment so that you can better understand any residual microbial risks in your system and develop a practical plan to reduce those risks to an acceptable level.
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