Sedimentation efficiency evaluation of an aquaculture tank through experimental floc characterization and CFD simulation

One of the most important parameters for the proper functioning of an aquaculture tank is water quality. The survival and healthy growth of fish depends on it. The main factors affecting water quality are the remains of food and feces of fish which form cohesive particles called flocs that are kept within the tank or in the modules of the recirculating aquaculture system (RAS). Through the application of non-invasive optical techniques such as particle tracking velocimetry (PTV) it was possible to experimentally characterize the particles from aquaculture tanks obtaining diameters and settling velocity distribution, which allowed estimating the effective density of the flocs. With these parameters, the discrete phase model (DPM) was applied using computational fluid dynamics (CFD) to estimate the position and velocity of the particles within a prototype tank with geometry that promotes hydrodynamics suitable for particles sedimentation while maintaining the conditions for fish growth. Through an experimental validation it was verified that by having a tank with circular geometry, central settler made of concentric cylinders, perimeter gratings and outlet spillway cone, it is possible to achieve an efficiency of 77.91–90% of particles sedimentation not exceeding 1 h in the process. Thus, through computer simulation coupled with experimental validation, it was possible to establish geometric parameters for the design of aquaculture tanks with self-cleaning characteristics under the sustainable scheme of water recirculation and reuse.