Abstract:To optimize recirculating aquaculture systems (RAS), we performed a water-quality detection experiment to study the effect of clearance rates of ammonia nitrogen, chemical oxygen demand (COD) and suspended solids (SS) by a biological filter in RAS under conditions of ammonia nitrogen and dissolved oxygen load. The experimental results for ammonia nitrogen load showed that the ammonia nitrogen concentration of the inlet water had a significant effect on the ammonia nitrogen (positive correlation) and COD (positive correlation) of the outlet water (P<0.01), and did not have a significant effect on SS. The optimal treatment effect of the water was observed when the ammonia nitrogen concentration of the inlet water was 0.45~0.65 mg/L (average clearance rates of ammonia nitrogen, COD, and SS were 82.1%±3.3%, 7.1%±1.5%, and 5.8%±1.6%). Experimental data for the dissolved oxygen load showed that dissolved oxygen concentration had a significant effect on ammonia nitrogen (negative correlation) and COD (negative correlation) treatment (P<0.05), and did not have a significant effect on SS. The optimal treatment effect of the water was observed when the dissolved oxygen concentration was 5.0~7.0 mg/L, (average clearance rate of ammonia nitrogen, COD, and SS were 78.7%±3.5%, 23.0%± 5.3%, and 7.1%±2.0%). Therefore, when the concentration of ammonia nitrogen is 0.45~0.65 mg/L, the concentration of dissolved oxygen is 5.0~7.0 mg/L. The treatment effect of ammonia nitrogen, COD, and SS is optimized by the coral biofilter of RAS in this experimental environment.
