The issue of using treated wastewater to provide an environmental benefit to rivers impacted by climate change has been a vexed one for many years. Increasing volumes of discharges from treatment plants into receiving streams, particularly those impacted by dwindling natural inflows due to climate change, has seen undesirable dilution ratios becoming prevalent. Additionally, the growing awareness of emerging contaminants and their potential environmental ramifications has heightened concerns of river advocacy groups.

The CWA does not believe the case for using treated wastewater in flow stressed streams for supposed environmental benefit has been made. Simply providing base flows or timing discharges to mimic environmental flows is not enough when the detrimental impacts of treated water on our waterways are for the most part already well understood. It is time to engage the wider community on this issue and have the type of conversations which honour the role of community in catchment management.

A brief history of issues at the Kyneton treatment plant

In 2019 there was a major spill into the Campaspe River from the Kyneton Water Reclamation plant.

Coliban Water (CW) was subsequently fined and placed on a 2 year good behaviour bond. Community feedback from Coliban Water engagement delivered:

“key themes involving the plant to only produce and release low-nutrient, low-e-coli Class B water to the river in future, and to abandon the measurement of river flow at its current gauging station at Redesdale.”

CW proceeded to spend $17 million in upgrades via the Kyneton Solutions Project.



During construction water releases were required to comply with the then current licence conditions.

Discharges were required to meet water quality parameters and be released at a maximum ratio of 20 per cent treated water to 80 per cent river flow at Redesdale.

This was in keeping with a reasonably standard EPA dilution ratio.

However the Redesdale gauge is, for unclear reasons, 22kms below the WRP outfall at Kyneton.

This distance was the main factor of why CW was able to comply with the stipulated dilution ratio.

Once the measurement was rightly taken at the source of the discharge CW was always going to struggle under the current arrangements to comply.

Licence negotiations

CW spoke to the EPA regarding a licence renewal to account for the upgrades along with a change in gauging station location from Redesdale to upstream of the Kyneton outfall. CW also undertook to do 7kms of fencing on the Campaspe River as a nutrient offset and funded other projects such as works on Snipes Creek as part of their court ordered fine.

The EPA, in acknowledgement of the changed location agreed to a 2:1 dilution at Kyneton which was below their normal standard.

16 September 2021 EPA Correspondence with Coliban Water:

“EPA takes a conservative stance to ensure environmental benefits are delivered, and considers a 2:1 dilution (river water to treated water discharged) appropriate.”

March 2022 An application to commence the review was submitted by CW. Acceptance by the EPA in May 2022 started the process. 

Summary Document for Kyneton WRP EPA Licence Amendment Application May 2022 quoted:

“that the amended discharge licence for the Kyneton Water Reclamation Plant will be: • protective of, and likely improve, river health • protective of downstream beneficial uses”

“The discharge of only BNR-treated water to the river will result in: • A decrease in the annual volume of treated water that will be discharged • An improvement in the quality of the treated water that will be discharged. In practical terms, this improvement in discharge quality will result in: • At least a 50% reduction in the annual load of total nitrogen going to the river • At least a 95% reduction in the annual load of total phosphorus going to the river • An improvement in pathogen management through the installation of an upgraded UV”

“for the period from 1933 to 1996, as measured at the Ashbourne gauging station, is compared to the median streamflow for the period from 1997 to 2021, there has been an 83% decrease in median streamflow between the two periods.”

“It is recognised that the value of 66.7% is greater than the 33.3% figure that EPA put forward in Attachment G, but, based on a comprehensive assessment of the available date, and the supporting documentation that accompanies this summary document, it is considered that this dilution ratio will be protective of the beneficial uses of the river.”

CW stated: “Despite the change to the dilution ratio, the overall volume of water released to the Campaspe River under normal operations will decrease.”

“A major outcome of the Kyneton Solution Project is the water reclamation plant will no longer need to undertake blended water releases to the Campaspe River. The only water that will be released to the river, under normal operating conditions, will have been treated onsite by the Biological Nutrient Removal (BNR) process.”

“A change in the dilution ratio for the release of treated water to the river will shift the ratio from up to 20% for passing river flow to up to 66.7% of passing river flow.”

“The change is supported by the improvements made in the quality of water that will now be released to the river, in addition to the river health works completed and the Environmental Risk Assessment undertaken. Beneficial uses of the Campaspe River are protected with this increase to the dilution ratio.

The following map and tables are from:

Assessing the Benefits of Environmental Offsets on the Condition of the Campaspe River: Year 1 (2018-2019), Technical Report #22. Aquatic Environmental Stress Research Group, RMIT University, Victoria, Australia.

This image has an empty alt attribute; its file name is CW-Offsets-Report-Monitoring-Sites.jpg

The dotted blue line in Fig 15 indicates the outfall lying between site 6 and site 7 (see above for map).

This clearly illustrated a detrimental impact from treated waste discharges from the Coliban Water Treatment Plant into the Campaspe River.

The effect is still evident well downstream.

The dilution factor of treated water from the plant to river flow remained a major dispute between Coliban Water and the EPA. As can be seen from the composite table below, because of the usually smaller volumes of river flow at the new gauge in Kyneton, Coliban Water felt they were going to struggle to comply with the EPA’s concession of 33% treated effluent to river flow for the full year.

Derived from

The Decision

Ultimately CW got its way and the VCAT agreed amendments were finalised and the EPA conceded to CW the ability to discharge at up to 66% treated effluent to river water for up to 30% of the annual discharge at the Kyneton gauge. This is in comparison to the EPA’s original preferred dilution factor of 33% which now only holds for the balance of the annual discharge.

In doing so the EPA has set a concerning precedent and there is little doubt water authorities seeking to increase the discharge loads of treated wastewater into receiving streams will move for similar concessions.

A list of the documents presented at VCAT can be found on the EPA website for now at:

CWA Questions

What is the science behind the EPA declaring “environmental benefits” for treated water disgorged into waterways? What does this mean: “EPA takes a conservative stance to ensure environmental benefits are delivered“?

How many other waste water treatment plants do, or are about to, exceed dilution limits due to decreased stream flows in the receiving waterways?

Given the decreased flows in our waterways due to climate change, will this continue to pressure higher permissible dilution levels for volumes of treated waste water into waterways? What implications are there for standardised load limits for contaminants such as phosphorus and nitrogen, and do they need revision?

How is the emerging contaminants issue being incorporated in the EPA and VCAT decisions around dilution limits?

Do the Essential Services Commission’s price determinations play a role if any in the apparent under-investment in treatment plants as exposed in this case?

Why isn’t the increased risk of contamination of waterways receiving treated waste water a priority climate change mitigation issue of government?


The EPA has released its guidelines to the discharge of treated wastewater into surface water. It can be found here.

In response the Concerned Waterways Alliance members critiqued the document which can be found here.