Nature-based solutions to wastewater

With water utilities and local councils increasingly looking at nature-based solutions, a project out of Millowl (Phillip Island) is providing opportunities to reduce greenhouse gas emissions.

Westernport Water has teamed up with scientists to explore how floating wetlands can be used in wastewater treatment. The two-year research project involves installing a floating wetlands system on a wastewater lagoon at Cowes Wastewater Treatment Plant.

Together with scientists from Deakin University and CSIRO, Westernport Water will monitor the plants over 18 months to determine how effective they are at absorbing nutrients, which is expected to reduce emissions and contaminants from the water.

The project’s initial stages have been promising, and the completion date is set for mid-2025. Dona Tantirimudalige, the Managing Director of Westernport Water, has been a major driver of the project.

“I do love a pilot program because I think you can only desktop test things to a certain extent,” she said. “The goal was to test some hypotheses around how we could use nature-based solutions to lower greenhouse gas emissions, improve water quality and extract emerging contaminants.”

“This pilot program was directly related to a larger-scale project that we are hoping to begin building in 2025. The learnings from the pilot program will feed directly into this 60-megalitre recycled water wetland.”

Zoe Geyer was intrigued by the project due to the perceptions of the water industry focusing predominantly on pipes and storage. As Westernport Water’s Climate Change Senior Advisor, she was the project manager and thrilled to be part of this future-ready transition mindset.

“I believe that nature-based systems could provide opportunities for resilience and our climate adaptation goals,” said Geyer.

What is the project?

The floating wetlands project uses wetland plant species suspended on the water column with roots submerged in the water. The plants take up nutrients and contaminants from the water and hold these in their plant material.

Every six months, the nutrient-filled plants are harvested, allowing new growth so the cycle can continue. The harvested plants have the potential to be reused, composted, or turned into biochar. The floating wetland pilot trial was part-funded by the Department of Energy, Environment and Climate Action (DEECA) as a key priority project in the Western Port IWM Forum Area. The findings are being used to inform the approach to the use of nature-based solutions, particularly for a 60ML wetland storage system at King Road Wastewater Treatment Plant.

This unique project attracted Shaun Ratten, a team leader at Westernport Water. As an operator within the water industry, he was intrigued by the possibilities.

“No one else in Victoria was doing this floating wetland project, and being a part of the project from the start was a great opportunity. As I got increasingly involved, I was recommended to present my insights into the project to the network operator development course,” said Ratten.

The project sought to manage treated effluent and emissions produced by wastewater treatment plants. Working with the CSIRO and Deakin University, Westernport Water wanted to find a nature-based solution.

Adding an additional, all-natural filtration step into the wastewater treatment process will improve the quality of water discharged into the ocean, keeping the natural environment healthier and reducing the risk of nutrient pollution. In addition, floating wetlands minimise greenhouse gas emissions by capturing and storing carbon that would otherwise be emitted into the atmosphere as greenhouse gases.

Other benefits include increased biodiversity, improved bioremediation opportunities, enhanced water security and cost savings.

Outcomes so far

The project is still ongoing, but there have been some learnings. Geyer has been at the forefront of the project and has found that nature-based solutions can take some time to adapt to the conditions.

“We need to plan for the establishment phase for future projects,” she said. “By looking at nutrient removal, greenhouse gas emissions reduction and emerging contaminants uptake, we have seen some changes during the establishment period. We have not yet seen a significant change in nutrient reduction, but that could be attributed to that establishment year. There is variability in the growth of plant species during this period. Despite this difference, we are seeing those plants take up some of the contaminants.”

Geyer also noted some initial trends in reducing greenhouse gas emissions, which shows that one of the original goals could come to fruition.

“We’ve seen some practical learning around implementing this project,” Tantirimudalige said. “From that perspective, nature-based solutions take longer as well. We have a little bit of flex that we need to build into our expectations when building nature-based solutions.”

Tantirimudalige pointed out that all the learnings will feed into increasing the knowledge base. Tenders recently closed for the concept and design stage of the 60-megalitre recycled water wetland that Westernport Water plans to build.

There has been considerable interest from across the water and wastewater industry, with a site visit opportunity during OzWater’24, and an upcoming visit as part of the Australian Water Association (AWA) Regional Study Tour 2024 for young water professionals.

“People have sought us out and talked to us about the project. We are comparing notes with other water corporations, who are looking to do similar projects within their own catchment, “Tantirimudalige said. “Some have had conversations with us before they started on their projects. Such collaboration creates further ideas and thoughts.”

The future of the project

With a nature-based solution, Westernport Water believes there are many opportunities for the next stage of the project.

“It’s important to remember that we all exist in an ecosystem,” said Tantirimudalige. “And we need to think about how we exist within that ecosystem in a complementary way. There are many organisations that could benefit from this shift at a broader ecosystem level.”

Geyer believes that the knowledge gained from nature-based systems will be critical to Westernport Water’s core business and to assessing climate adaptation resilience.

“We also need to look at how Westernport Water maintains land holdings, improves the health and biodiversity of the land, and improves the resilience of our society,“ Geyer said. “We are looking at how we can introduce complementary or even new systems within our current procedures to increase resilience and preparation for the future.”

Ratten sees the project as something that could be expanded further, whether it is filling a whole lagoon or across multiple lagoons.

“It would work a lot better if it went across the whole lagoon, and across multiple lagoons is even better,” he said.

For more information, visit www.westernportwater.com.au and vicwater.org.au