Performance evaluation of radial/vertical flow clarification applied to recirculating aquaculture systems

A prototype radial/vertical clarifier with 60° cone bottom was built and evaluated for application in recirculating aquaculture. Samples were analyzed for particle size distribution using a laser diffraction particle analyzer (Mastersizer S, Malvern Instruments Ltd., Worcestershire, UK) and total suspended solids (TSS) to determine the effectiveness of the clarifier. Surface area calculated mean influent and effluent particle diameters were 81.12 ± 1.57 μm and 54.48 ± 0.79 μm, respectively—a 33% reduction in mean particle size. Mean particle size within the system was 73.19 ± 1.37 μm. Mean influent and effluent particle diameters, based upon volume, were 340.62 ± 3.59 μm and 176.07 ± 2.37 μm, respectively, with a resulting overall particle size reduction of 48%. Average TSS was relatively low at all sampling points, 11.4 mg/L, 2.1 mg/L and 2.6 mg/L for influent, effluent and system sampling points, respectively, with a resulting average removal rate of 82%. The authors believe the suitability of radial/vertical flow clarifiers as a water efficient, low cost alternative solids collection device for recirculating aquaculture was demonstrated.