1 research outputs found
Nitrate Removal Performance of Denitrifying Woodchip Bioreactors in Tropical Climates
In Australia, declining water quality in the Great Barrier Reef (GBR) is a threat to its marine ecosystems and nitrate (NO3β) from sugar cane-dominated agricultural areas in the coastal catchments of North Queensland is a key pollutant of concern. Woodchip bioreactors have been identified as a potential low-cost remediation technology to reduce the NO3β runoff from sugar cane farms. This study aimed to trial different designs of bioreactors (denitrification walls and beds) to quantify their NO3β removal performance in the distinct tropical climates and hydrological regimes that characterize sugarcane farms in North Queensland. One denitrification wall and two denitrification beds were installed to treat groundwater and subsurface tile-drainage water in wet tropics catchments, where sugar cane farming relies only on rainfall for crop growth. Two denitrification beds were installed in the dry tropics to assess their performance in treating irrigation tailwater from sugarcane. All trialled bioreactors were effective at removing NO3β, with the beds exhibiting a higher NO3β removal rate (NRR, from 2.5 to 7.1 g N mβ3 dβ1) compared to the wall (0.15 g N mβ3 dβ1). The NRR depended on the influent NO3β concentration, as low influent concentrations triggered NO3β limitation. The highest NRR was observed in a bed installed in the dry tropics, with relatively high and consistent NO3β influent concentrations due to the use of groundwater, with elevated NO3β, for irrigation. This study demonstrates that bioreactors can be a useful edge-of-field technology for reducing NO3β in runoff to the GBR, when sited and designed to maximise NO3β removal performance