Transport analysis of particulate matter in media-saturated mesh tube filter for the desalination primary pretreatment process

Abstract Roughing filters (coarse media filtration) are a type of porous media filters used as pretreatment systems when the raw water contains a large amount of suspended particles and organic matter. Mesh tube filter media, roughing filter media composed of LDPE, are used in the process of removing suspended particles in wastewater treatment. In this study, we investigated the transport of suspended solids in saturated mesh tube filter media using kaolin particles (sizes range: 0.5–40 μm) and spherical SiO2 particles with particle sizes of 1.5, 10.4, and 19.5 μm. The results showed that the mesh tube filter media effectively removed suspended particles at sizes of 1–20 μm, and the removal rate of suspended particles under artificial seawater conditions was 5–50% higher than under freshwater conditions. It was also found that mechanism of removal of suspended particles varies with the velocity of the fluid by mass balance analysis. With high ion concentrations in the seawater conditions, the size of the suspended particles increased by 5–20%, which caused the suspended particles to be more strongly affected by gravity. The DLVO interaction energy analysis showed that the electrical attraction between suspended particles and filter media increased strongly in artificial seawater conditions.