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NDMA unlikely concern for SEQ
 The good news resulting from UWSRA research undertaken by Dr Nicole Knight in SEQ is that disinfection by-products (DBPs) such as nitrosodimethylamine (NDMA) and trihalomethanes (THMs) are unlikely to be a concern for SEQ’s drinking water.
Dr Knight is a research fellow at Griffith University who has been working with Glen Shaw from Griffith and colleagues from The University of Queensland (UQ) on UWSRA’s DBP Formation and Minimisation in Drinking Water project.
NDMA and THMs can be formed during the water treatment process as a by-product of disinfection by chloramine and chlorine. Their occurrence in drinking water is strictly controlled through the Australian Drinking Water Guidelines.
The team has been examining DBP formation potential in seven SEQ source waters to identify any current or emerging issues.
Dr Knight said one major finding was that SEQ should not have any problem complying with Draft Australian Drinking Water Guidelines introduced earlier this year, as no NDMA was found in any of the finished waters.
She said the absence of NDMA was partly due to the fact that SEQ source waters were not highly wastewater impacted but also because water treatment plants were using appropriate treatment methods.
“There’s one plant in SEQ that uses polyDADMAC as a coagulant aid (to remove organic matter that could react with disinfectants to form by-products), which has NDMA precursors,” Dr Knight said.
“However, we were able to confirm that that plant did not have any detectable NDMA (<5 ng/L) in their finished water and that’s probably because they use chlorination.
“It’s an important outcome for operators to know that if they are using polyDADMAC, they should be able to safely use chlorination, whereas using chloramination could see a large increase in NDMA formation potential.”
Dr Knight said the research also indicated THM formation potentials of SEQ’s source waters were consistently below the Australian Drinking Water Guidelines of 250 μg/L.
She said another important outcome of her study was that enhanced coagulation, commonly used in early stages of water treatment, had different outcomes for water containing high levels of bromide.
“Bromide is not removed in the enhanced coagulation process, which would normally lower formation of DBPs such as THMs, and can actually increase total THMs in high bromide source waters.
“While it’s been previously observed that you can get an increase in brominated THMs after enhanced coagulation, to my knowledge this is the first time an overall increase in total THMs has been observed.”
Dr Knight said one of the next priorities for the project team was looking at novel strategies for removing bromide.
She said she would also be working with UQ’s Dr Maria José Farré Olalla on a project that will include developing analytical methods for emerging DBPs.
“Maria and I will work to find an appropriate surrogate or indicator for DBPs arising from chloramination and we’re also going to be looking at if there are any particular risks for DBP formation arising from combining water from different sources in the distribution system,” Dr Knight said.
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