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This study investigates the efficiency of a biological nitrogen removal system for aquaculture effluent treatment of a down-flow hanging sponge (DHS). The experiment has been performed for 212 days. The DHS system had hydraulic retention time (HRT) decrease from 8 hours to 1 hour (8 hours, 5 hours, 3 hours and 1 hour). From the experiment data showed that the amount of ammonia after passing through the system at an HRT 1 hour there was 0.42 mg-N/L. The system provided average removal efficiencies for ammonia and Total nitrogen of 99% and 69%, respectively. The water quality profile results revealed the ammonia, BOD, SS and VSS are most eliminated in the first segment of DHS system. DHS system can perform nitrification reducing ammonia (NH3) toxicity in aquaculture wastewater. The study confirmed that the DHS system provided nitrification process and the overall DHS system provided high-performance aquaculture effluent treatment system.
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