Sandy Beach Bioreactor showing monitoring stations (white pipes).
Sandy Beach Bioreactor showing monitoring stations (white pipes). Contributed

Reducing nitrate run-off

WORKING towards reducing nitrate run off on blueberry farms, a new trial of wood chip bioreactors has been under way in the area with promising results.

The trial has been held by the North Coast Local Land Services on the Coffs Coast, with the help of local growers.

The bioreactors were constructed in Bucca Creek and Sandy Beach earlier this year to test their effectiveness in two growing areas in the region.

A recent water quality analysis on two three hectare farms revealed at least a 75% reduction in nitrate concentrations after passing through the reactor.

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

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 nutrient management.

"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.

"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."

"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"

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.

The trial is part of the Blueberry Engagement Project North Coast LLS has undertaken in partnership with Coffs Harbour Regional Landcare and is funded by the Australian Government under the National Landcare Program.

For more information on bioreactors, call Shaun Morris on 6659 9402 or email shaun.s.morris@lls.nsw.gov.au