Sweeter water

The project is led by Jaragun Pty Ltd, in partnership with local farmers, the Babinda Swamp Drainage Board, James Cook University researchers, the Queensland Department of Agriculture and Fisheries, Terrain NRM, and Australian Wetland Consulting.

With a $438,894 three-year grant from the Queensland Government’s Reef Water Quality Program Great Barrier Reef Innovation Fund, the trials will be conducted on two different farms in the Babinda Swamp Drainage Area of the Russell River catchment.

“This region has been identified as a hotspot for dissolved inorganic nitrogen in the Great Barrier Reef catchment, so it’s the perfect place for the first trial of denitrification bioreactors in the Wet Tropics,” JCU researcher Dr Alex Cheesman said.

“We’ll be building two different configurations of bioreactors on two farms with two contrasting soil types that are characteristic of the Babinda Swamp area,” Dr Cheesman said.

Denitrifying bioreactors route water through a high-carbon material (the trial will use woodchips) under anaerobic conditions to encourage denitrification.

“The aim is to convert dissolved inorganic nitrogen in the drainage water to atmospheric nitrogen, or N_2,” JCU researcher Associate Professor Paul Nelson said. “As seventy per cent of the atmosphere is made up of N₂, which is not a greenhouse gas, it means the nitrogen can disperse without harm to the reef.”

Director Liz Owen said Jaragun was pleased to be working with stakeholders to contribute to better health for the reef lagoon.

“JCU’s expertise in sustainable agriculture gives us confidence that together we can develop an evidence-based argument for the best way to achieve this, in the challenging farming conditions of the Wet Tropics,” she said.

The researchers will assess the cost-effectiveness of the bioreactors under the region’s challenging rainfall and hydrologic conditions.

The bioreactors will form part of an integrated treatment train being established by Jaragun, including sediment traps and a constructed wetland, to manage dissolved inorganic nitrogen emanating from the Babinda Swamp Drainage Area.

“That integrated approach, along with the involvement of such a broad network of local stakeholders, is a real strength of this project,” Dr Cheesman said.

“We hope this will lead to on-farm bioreactors that can be used cost-effectively across the Russell catchment more broadly, as well as contributing to the production of state-wide guidelines on the design and use of denitrifying bioreactors.”

Media enquiries: linden.woodward@jcu.edu.au