Using denitrifying bioreactors to improve water quality on Queensland farms

The purpose of this document is to provide guidance on the use of denitrifying bioreactors to improve water quality, specifically to remove nitrate from agricultural land uses in Queensland. Bioreactors are passive, relatively unobtrusive, low maintenance treatment systems that can fit within a farm without impacting production, or farm operations. However, they are not a costeffective solution to improving water quality in all locations. Like any treatment system their suitability needs to be considered on a site-by-site basis, based on the landholder’s objectives, water quality, water regime, position in the landscape and specific siting constraints. These guidelines aim to guide the reader through these key considerations to help determine if a bioreactor is suitable, and if so, how to design, construct and maintain one to maximise its nitrate removal performance. This document collates and synthesises information from a range of bioreactor trials conducted in Queensland between 2015 and 2020, together with published literature on bioreactor research in other countries. The Queensland trials have predominantly been conducted on farms growing sugarcane and horticulture crops, as this is the dominant land use in coastal Queensland, contributing nitrate to coastal and marine ecosystems. Preliminary results from trials on aquaculture farms indicate that bioreactors can also be effective at removing nitrate from aquaculture wastewater. Therefore, these guidelines can also inform the use of bioreactors in intensively cultivated production systems, such as aquaculture, protected cropping systems (i.e. greenhouses) and nurseries. Please note, there is little or no published information on bioreactors specific to these production systems in Queensland. The primary audience for these guidelines is extension officers, natural resource managers and land managers seeking to design, install and operate denitrifying bioreactors in agricultural areas. These guidelines are also relevant to researchers, industry groups, policy officers and natural resource managers seeking passive nitrogen removal techniques