Health-based targets (HBT) help water utilities evaluate the safety of their drinking water, but a lack of resources and data can make assessment difficult for some regional water businesses.
Microbial HBT give a quantitative definition of drinking water safety using organisms that represent the major groups of pathogens: bacteria, viruses and protozoa.
The goal of HBT is to reduce the community burden of waterborne disease in drinking water to 1 millionth of a daily-adjusted life year (DALY). A DALY represents a lost ‘healthy’ year of someone’s life, whether through illness or death.
“Through HBT assessment, we look at the risks inherent in our source water and at how well our treatment plants perform in mitigating those challenges,” Viridis Consultants process engineer Glen Luscombe said.
“It’s about helping water suppliers quantify their risk and then providing strategies to help deal with them.”
Speaking ahead of his presentation on HBT at Ozwater’19, Luscombe said regional water businesses have been slow to implement the targets. This could be because they are waiting until HBT are added to the Australian Drinking Water Guidelines.
Supplying drinking water to hundreds of people, rather than tens of thousands, means smaller water businesses can struggle to undertake a HBT assessment, and implement changes as a result.
“There’s only been a patchy introduction of HBT so far; this is a concern across Queensland and New South Wales at the moment,” Luscombe said.
“If you’ve got a council with 1000 people in it, the notion of trying to find $1 million for new equipment can be a very big deal.”
Regional businesses also deal with diverse land use in their catchments – from plant-based agriculture to stock grazing, urban development and mining – which makes assessment more challenging. And some don’t have the resources to collect the type and amount of data needed.
“We like to have two years’ worth of data so we can correlate risks identified in a catchment with what level of infiltration is actually present in the source,’ Luscombe said.
“This is a challenge for many regional councils.”
However, it is possible for smaller councils to undertake HBT assessment and improve their operations.
Viridis Consultants worked with Mareeba Shire Council (MSC) in north Queensland to assess its four drinking water supply schemes, which range from 200 to 10,000 people.
The aim of the assessment was to get a better understanding of the pathogen risk within the supply system and develop a roadmap for providing protection to the community.
“They were a bit nervous about where this process might take them,” Luscombe said.
“Although MSC is not on the very small end, they are small enough that a major upgrade to their plant is a huge deal.”
Along with recommending MSC replace some filters and a reservoir, the Viridis team identified a range of operational, monitoring and catchment management strategies to improve the outcomes for each scheme.
This included: additional monitoring of E.coli levels in raw water; additional turbidity instrumentation to monitor individual filter performance; and improvements to operational processes, including the optimisation of filtration systems.
Luscombe said a focus on improving the operation of treatment plants can potentially delay the need for capital upgrades.
“One of the approaches that can be taken for HBT is not to focus unduly on the capital equipment itself, but to look at what your risks are and how you can manage that risk,” he said.
For example, the Good Practice Guide to the Operation of Drinking Water Supply Systems for the Management of Microbial Risk sets out the best way to operate a plant.
“This guide is often forgotten about … but by looking at the operation of plants, we can find things that are a bit more manageable for small suppliers to deal with,” Luscombe said.
“The biggest benefit I see of having a deep look at operations is that councils may find there are things they can do to delay capital renewal.
“By not focusing on the capital side so much, there are certainly opportunities for councils to limit the financial impacts of an HBT assessment.”
Register for Ozwater’19 to hear more from Glen Luscombe about health-based targets in regional drinking water supplies.