Ecotechnologies for Aquaculture Wastewater Treatment in a Water-Scarce Region

Abstract

In aquaculture, biological treatments usually have an excellent benefit-cost ratio. This study evaluated the efficiency of different ecotechnologies on aquaculture wastewater treatment. Two experimental units were installed. In the first one, tanks were individually vegetated with free-floating aquatic macrophytes. In the second experimental unit, 10.72 m² of artificial substrate were added for periphyton colonization. The hydraulic retention time of the wastewater was of 30 days. Both physical and chemical characterizations of the effluent were carried out at the beginning and at the end of the experiment. The periphyton community attached to the substrate was catalogued. In the first unit, the pH, nitrite, and orthophosphate values were significantly different. The tanks vegetated with Azolla filiculoides were the only ones where the electrical conductivity values were reduced. Tanks vegetated with Azolla filiculoides and Pontederia crassipes presented decreased the nitrate concentration. On the other hand, the concentration of ammonia and total phosphorus decreased in all vegetated tanks. In the second unit, only the nitrate and ammonia values did not decrease in the last day of the experiment. 33 taxa belonging to the classes Cyanophyceae, Chlorophyceae, Bacillariophyceae, Trebouxiophyceae, Coleochaetophyceae, Coscinodiscophyceae and Zygnematophyceae were identified in the substrate. The experimental units were effective in mitigating the nutrients in aquaculture wastewater that cause eutrophication. HIGHLIGHTS• We assessed ecotechnologies with aquatic macrophytes and with periphyton.• Azolla filiculoides, Pontederia crassipes and Salvinia auriculata were used.• Nutrient removal was greater using aquatic macrophytes than using periphyton.• Periphyton was not efficient in reducing the ammonia and nitrate contents.