Efficacy of a subsurface-flow wetland using the estuarine sedge Juncus kraussii to treat effluent from inland saline aquaculture

The major environmental issue facing the inland saline aquaculture industry of Western Australia is the treatment of nutrient and salt-enriched aquaculture effluent. Constructed wetland treatment systems could provide a simple and low-cost mechanism to remove these pollutants. Replicate plots of a pilot-scale, subsurface-flow wetland treatment system incorporating the estuarine sedge Juncus kraussii were constructed to test the relative efficacy of total nitrogen (TN), total phosphorus (TP) and sodium chloride (NaCl) removal. After 38 days, the wetland plots removed up to 69% of the TN load and 88.5% of the TP load, with active uptake by the soil-plant ecosystem being greatest at high nutrient levels. TN removal increased markedly over time, whereas TP removal remained relatively constant. Salinity did not affect TN removal, but did reduce TP removal. Although up to 54.8% of NaCl load was removed by the wetland plots, this appeared to be a passive consequence of water uptake. NaCl removal increased over time, but was not affected by either nutrient or salinity concentration. Growth traits of J. kraussii were adversely affected by salinity concentration but not by nutrient level.