Adsorption has been suggested as an effective method for removing phosphates from agricultural wastewater effluents that contain relatively high phosphate concentrations. The present study focused on the use of a bentonite-lanthanum clay (Phoslock®) for reducing the dissolved phosphate concentration in fishpond effluents. Batch experiments with synthetic phosphate-spiked solutions and with fishpond effluents were performed in order to determine adsorption equilibrium isotherms and kinetics as well as to determine the efficiency of Phoslock® in removing phosphate from these solutions. In the synthetic phosphate-spiked solution, the mean maximum phosphate adsorption capacity was 92 mg Phoslock®/mg phosphate removal. A ratio of 50, 100, and 200 mg Phoslock®/mg phosphate removal was found for complete phosphate removal from the fishpond effluents, where higher doses of Phoslock® led to a faster removal rate (94% removal within the first 150 min). These results show that bentonite-lanthanum clay can be employed for designing a treatment process for efficient phosphate removal from fishpond effluents.
Keywords: Adsorption; Aquaculture; Fishpond; Phoslock®; Phosphate; Water treatment.