Removal of Nitrite and Nitrate from Recirculation Aquaculture System Effluent (RAS) by Modified Bentonites

Document Type : Research Paper


1 Instructor of Fisheries, Faculty of Marine Science, Chabahar Maritime University, Chabahar

2 Assist. Porf. of Chemistry, Faculty of Sciences, Isfahan University, Isfahan

3 Assoc. Prof. of Fisheries and Environmental, Dept. of Natural Resources, Tehran University, Tehran

4 M.Sc. Student of Fisheries, Dept. of Natural Resources, Tehran University, Tehran


Water Treatment is among the most important water quality management criteria in recirculating aquaculture systems (RAS). Nitrogenous wastes are the main pollutants in RAS. Ion exchangers, namely zeolites and clays are widely used in wastewater treatment industries. Due to negative charges within their structural network, they are used frequenty. Through superficial modifications this process can be applied to remove anions as well as cations. In the present study, modification of superficial and layered structures of zeolite and clay were carried out using the organic compound, tetradecyltrimethylammonium bromide and different ambient conditions of temperature (10, 15 and 20oC) and pH (6.0, 6.5, 7.0, 7.5 and 8.0) were examined. Results showed that ambient factors such as temperature, pH, ion concentration, presence of excess anions and interfer ions could affect the extent of ion uptake. It was revealed that higher temperatures increased ion uptake by modified Bentonits. Temperature rise significantly affected nitrite uptake of both absorbents (p<0.05). Higher pH significantly influenced nitrate absorption of both absorbents in a positive manner, while in the case of nitrite it was not depicted. Results indicated that use of modified ion exchangers as a effective tool for anion uptake in RAS is feasible.


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