Separation performance of a low-pressure hydrocyclone for suspended solids in a recirculating aquaculture system

Abstract

The separation performance of a low-pressure hydrocyclone (LPH) was evaluated for suspendedsolids removal in a recirculating aquaculture system (RAS). The dimensions of the LPH were 335 mm cylinder diameter, 575 mm cylinder height, 60 mm overflow diameter, 50 mm underflow diameter, and 68° cone angle. The inflow rate varied (400, 600, 800, and 1,000 mL s-1) with 25%, 25%, 20%, and 10% of bypass (Rf), respectively. The maximum total separation efficiency (Et) and reduced separation efficiency (E't) for suspended solids from the effluent of the second settlement tank (before biofiltration) were 58.9% and 45.2%, respectively, at an inflow rate of 600 mL s-1 and 25% of Rf. The maximum Et and E't for suspended solids from the water supply channel (after biofiltration) were 24.4% and 16%, respectively, at an inflow rate of 1,000 mL s-1 and 10% of Rf. The maximum grade efficiency (Ei) was 51.6% for a 300 μm particle size at an inflow rate of 600 mL s-1 with 23% of Rf. The maximum reduced grade efficiency (E'i) was 37.6% for a 300 μm particle size at an inflow rate of 1,000 mL s-1 with 11% of Rf. The results indicate that the separation performance of the LPH for suspended solids removal was size selective and that maximum removal occurred at particle sizes ranging from 300 to 500 μm.