In early September 2024, Friends of the Earth applied to Melbourne Water in a Freedom of Information request concerning detections of PFAS chemicals since 2022 and pesticides in Melbourne's drinking water supplies since 2017. After a lengthy process information was provided on the 30th of December.
In terms of PFAS there were no detections. This is partly due to Melbourne Water's third round of PFAS testing which commenced in August 2024. Prior to this date, Melbourne Water conducted PFAS testing at seven locations between 2010-11 and 2014-17. PFAS chemicals were detected at Lilydale Water Treatment Plant in 2010 and also twice at the Yarra River offtake to Sugarloaf Reservoir in 2011 and 2015. It appears that PFAS chemicals have recently been detected by Melbourne Water, but they were detected after the FoI application was sent in.
In terms of pesticides, impacts on the Yarra River and Sugarloaf Reservoir have long been a concern to Friends of the Earth. Water from the Yarra River is pumped into Sugarloaf Reservoir where it is stored prior to treatment. The water is then treated at Winneke Treatment Plant before being distributed to Melbourne's northern and western suburbs. The Winneke Treatment Plant was never designed to properly filter out micropollutants such as pesticides, microplastics and PFAS.
There were 173 pesticide detections by Melbourne Water since November 2019. 155 detections (89.6%) were from the Yarra River near Sugarloaf, with a dozen detections after treatment at Winneke Treatment Plant. This represents the first time that pesticides have been detected after treatment at Winneke.
The detections after treatment from Winneke were all very low, with the highest being for Simazine at 0.06µg/L in November 2019. On the same day that Simazine was detected, the herbicides MCPA and Metolachlor were also detected at 0.02µg/L. In terms of drinking water guidelines, the Australian Drinking Water Guidelines have a guideline for Simazine set at 20µg/L, MCPA at 40µg/L and Metolachlor at 300µg/L. There were eight separate dates between 2019 and 2024 when pesticides were detected after treatment at Winneke.
If Winneke is already having issues with filtering out pesticides at 0.02µg/L, how will it deal with PFAS and other chemicals under this amount? A major concern, in terms of micropollutants such as PFAS, is that the majority of PFAS chemicals may not be PFOS, PFHxS and PFOA which are the only PFAS chemicals with drinking water guidelines and the only PFAS chemicals that water authorities generally publish results for. Recent PFAS testing by Goulburn Valley Water detected a range of PFAS levels at between 2ng/L-10ng/L (0.002µg/L - 0.01µg/L) across 37 water supplies. Interestingly Goulburn Valley Water detected PFAS in forested 'closed' water supply catchments, which also make up the bulk of Melbourne's water supply catchments. The most commonly detected PFAS chemical detected by Goulburn Valley Water was PFBS. Goulburn Valley Water tests for PFAS chemicals at levels which Melbourne Water testing will not detect.
In 2017 the Victorian State Government estabished the Wilip-Gin Birrarung murron Act in order to protect the Yarra River/Birrarung for future generations alongside traditional owners and the community. The legislation identifies the river and its corridor as a single living and integrated natural entity for protection. It is unclear how (or if) this act protects Birrarung from toxic pollution. Agricultural chemicals would be one of multiple toxic pollution sources entering Birrarung.
Guideline levels for some pesticides and other contaminants are listed in the ANZECC Guidelines. The Draft Guideline Values (DGV's) are an attempt to set levels for contaminants in a way that supposedly protects the majority of species in freshwater and marine waters.
Of the pesticides detected by Melbourne Water, five of the detected pesticides have ANZECC Guidelines. In terms of the two most frequently detected pesticides in the Yarra River, Metolachlor has a 99% DVG/trigger level 726 times lower than Simazine. Clearly Metolachlor is the worst 'offender' in terms of possible ecological impacts. Metolachlor even has a lower ANZECC 99% DVG/trigger level than PFOS. Metolachlor also has a 99% DGV over 21,000 times less than Glyphosate
Metolachlor is a herbicide used to control certain annual grasses and broadleaved weeds. In the upper Yarra Catchment its main use would be on pastures and on barley and oat crops but also would be allowed to be used in vegetable crops such as beans, maize, sweet corn, broccoli, cabbages, brussels sprouts and cauliflowers. S-Metolachlor was banned in Europe in 2023 due largely to water pollution issues and after concerns were raised particularly in France.
Metaloachlor is toxic to aquatic plants and algae. Essentially then, Metolachlor leaching into waterways could impact the base of the aquatic food chain further creating problems for primary consumers such as zooplankton, small fish and crustaceans.
Previous to 2010 almost no pesticide testing in the Yarra River occurred by Melbourne Water. 51 positive pesticide samples had been detected between 2010 to 2017. That represents a quarter of the total amount of detections between 2010-2024, meaning that 75% of positive pesticide samples at the Yarra River offtake have occurred since 2020, with the bulk occurring in 2021.
