SRDC Research Project final report Development of a constructed wetland for improving water quality in sugarcane drainage, and ensuring its community acceptance and industry adoption

Abstract

Canefield drainage water quality is an increasingly important issue for the industry and community because of the potential downstream environmental impacts of contained contaminants. The community is increasingly environmentally conscious, and many perceive agriculture as the main threat to environmental sustainability. Hence, regulators are tightening controls on polluted drainage from agricultural industries. As in other parts of the World, this trend will continue in Australia and agriculture is likely to be required to meet the same standards as other industries. The sugar industry must therefore develop and implement best management to address the issue, and better demonstrate and communicate their environmental stewardship. The means by which the NSW Sugar Industry faced and achieved a win-win outcome with respect to problems with their acid sulfate soil management is discussed in detail by White et al. (2007). This provides a model for managing drainage water contaminanation. PhD research by Green (2005) tested a number of techniques for ameliorating acidy in drainage from Robert Quirk’s 100 ha cane farm on the Tweed River. This research showed that most (>70 %) of the acidity in the farm’s drain water was in the form of the dissolved metal ions, particularly of iron and aluminium. Many mine sites also have this problem and a commonly used management tool is a constructed and vegetated wetland. Therefore the SRDC-funded project UNW003 constructed an approximately 1.5 ha wetland adjacent to the farm’s outflow drain. Natural recruitment, predominantly of Couch grass and Spike rush, established dense vegetation in the wetland. During rain-driven acid discharge events, water from this drain (about 10 % of the discharge) was pumped into the first of six terraced wetland bays and from there it flowed down to outflow into the discharge drain. During 3 years of operation, water quality was measured at the input, throughout, and output of the wetland.