A Comparative Study of the Purification of Aquaculture Wastewater Using Water Hyacinth, Water Lettuce and Parrotʹs Feather

Water hyacinth, water lettuce and parrotʹs feather plants were examined for their ability to remove nutrients from aquaculture wastewater at two retention times. During the experiment, the aquatic plants grew rapidly and appeared healthy with green color. At hydraulic retention times (HRTs) of 6 and 12 days, the average water hyacinth, water lettuce and parrotʹs feather yields were 83, 51 and 51 g (dm) m-2 and 49, 29 and 22 g (dm) m-2, respectively. The aquatic plants were able to significantly reduce the pollution load of the aquaculture wastewater. The TS, COD, NH4+-N, NO2--N, NO3--N and PO43--P reductions ranged from 21.4 to 48.0%, from 71.1 to 89.5%, from 55.9 to 76.0%, from 49.6 to 90.6%, from 34.5 to 54.4% and from 64.5 to 76.8%, respectively. Generally, the reductions increased with longer retention times and were highest in compartments containing water hyacinth followed by compartments containing water lettuce and parrotʹs feather. In terms of COD, NO3-- N and PO43--P, the effluent leaving the hydroponics system was suitable for reuse in aquaculture. However, the effluent had slightly high levels of TS, NH3-N, NO2-- N and pH after treatment.