The Plight of the Washing Machine
By: Carmen SnowdonRead more
It's #TechnicalTuesday so #teamWRc Engineer David Shepherd is discussing disinfection policy and water quality regulations in the UK and further afield.
The Australian Drinking Water Guidelines were recently revised to include treatment targets derived from quantitative microbial risk assessment (QMRA) and a defined health-based target (HBT) to assure the microbial quality of drinking water. This approach is recommended by the World Health Organization’s Guidelines for Drinking-Water Quality (GDWQ) and is embedded in US and Dutch regulations and in Canadian guidelines. It was proposed for, but not adopted by, the recast EU Drinking Water Directive. Fundamental to it is the concept of tolerable risk as quantified by the HBT, the corollary of which is that treatment does not provide an absolute barrier to pathogens.
UK regulators do not prescribe how water undertakers frame their disinfection policies. UK water quality regulations define disinfection in terms of removing or rendering harmless ‘every’ pathogen, seemingly inconsistent with the HBT concept. However, the Drinking Water Inspectorate recommends the GDWQ as a reference for informing disinfection policy.
WRc has been exploring uses of QMRA/HBT for a decade, through its Disinfection Forum and by working with individual water companies to review their disinfection policies. Other applications are being identified, for example to assess potential health risks from exposure to treated sewage effluent used for irrigation.
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Senior Process Engineer
David is a senior process engineer with a background in potable water treatment. David has worked on design and operation of water treatment processes, and has been involved in the development of process simulation software, including the addition of new process models, updating documentation, and provision of support and training courses for users