Effect of Mesh Size on Microscreen Filtration Combined with Foam Fractionation for Solids Removal in Recirculating Aquacultural Seawater

Abstract

AbstractMicroscreen filtration and foam fractionation have been considered as effective solids removal technologies in marine recirculating aquaculture systems (RAS). To figure out the appropriate mesh size for highly efficient solids removal and management, this study investigated the effects of different mesh sizes (120, 90, 60, and 40 μm) on a combination treatment of solids filtration and fractionation removal in RAS for grouper. The experimental results showed that filtration and total removal efficiency increased with the decrease of mesh size on the whole; however, the produced fine particles (<20 μm) increased simultaneously due to the breakup of relatively large particles caused by filtration. Although the best total removal efficiency was 32.33%, obtained with mesh size 40 μm, it was accompanied with a serious particle breakup. We suggest that the large amounts of fine particles are a big risk. Therefore, 60‐μm mesh was better in terms of solids removal efficiency and fine particles management. The effect of mesh size on microscreen filtration was undoubted, while the indirect effect on foam fractionation was negligible. However, fractionation could be effective for removing partial fine particles and its efficiency was quite close to that of filtration. Foam fractionation is thus recognized as an essential treatment in marine RAS.