North Coast Local Land Services has been working to trial the effectiveness of wood chip bioreactors to reduce nitrate runoff

With the help of local growers North Coast Local Land Services has been working to trial the effectiveness of wood chip bioreactors to reduce nitrate runoff on Blueberry Farms and early results look very promising.

Bioreactors were constructed in both Bucca Creek and Sandy Beach earlier this year to test their effectiveness in the two most prolific growing areas in the region. The trial is part of the Blueberry Engagement Project North Coast LLS has undertaken in partnership with Coffs Harbour Regional Landcare and funded by the Australian Government under the National Landcare Program. Since 2014 this project has worked closely with the Blueberry industry in the Coffs Harbour area to provide them with the latest best management practices for soil, biodiversity and now nutrient management.

Shaun Morris, Senior Land Services Officer, said, “Woodchip bioreactors have been used successfully in North America and Queensland to reduce nitrate runoff into sensitive aquatic habitats from intensive horticulture production systems”.

“The main difference between this previous work and our trials is that we are dealing with high volume surface flows not gentle sub-surface groundwater flows and so the reactors have to be built to capture and treat nitrates while withstanding the effects of a variety of rainfall intensities and durations”

“It was positive to see a recent snapshot water quality analysis on two 3ha farms that showed at least a 75% reduction in nitrate concentrations after passing through the reactor” Shaun said.

“The woodchip serves as a carbon substrate for nitrate hungry bacteria that naturally reside in the nearby soil profile. Bioreactors typically have a life span of over 20 years and are well recognised for being considerably more efficient and environmentally friendly than other types of denitrification tools such as constructed wetlands.”

North Coast Local Land Services will be working closely with growers, Southern Cross University’s National Marine Science Centre and Coffs Harbour Council to monitor a variety of bioreactor designs over the next 12 months using funds from the Environmental Levy. This study will test the effectiveness of the bioreactors over the wettest periods of the year and provide the guidance necessary for them to be utilised by the Industry on a broader scale. 

“Reactors have to be specially designed to meet the needs of each farm. A range of calculations and considerations have to be undertaken to ensure the structure works efficiently and doesn’t impede on the day to day operations of the grower or farm infrastructure” Shaun said.

Blueberry and protected cropping growers interested in bioreactors can make enquiries with Shaun Morris, Senior Land Services Officer at Coffs Harbour by phone 6659 9402 or email via shaun.s.morris@lls.nsw.gov.au

Sandy Beach Bioreactor showing monitoring stations (white pipes).

Sandy Beach Bioreactor showing monitoring stations (white pipes).