Effect of magnetic field on calcium - silica fouling and interactions in brackish water distribution systems

Abstract

Fouling growth in brackish water distribution systems (BWDS), especially calcium-silica fouling, is inevitable issue in brackish water desalination, chemical and agricultural industry, eventually threaten the cleaner production process and environment. Magnetic Field (MF) has been a greener and effective technology to control calcium carbonate fouling. However, the effects of MF on composite calcium-silica fouling are still elusive. Therefore, this paper assessed the effect of MF on calcium and silica fouling. We found that MF not only significantly reduce the calcium carbonate fouling, but also obviously decreased the silica fouling. The MF reduced the calcite fouling reached 38.2%–64.3% by changing water quality parameters to trigger the transformation rate of CaCO3 crystal from compact calcite to looser aragonite, as well as increase the unit-cell parameters and chemical bond lengths of calcite and aragonite. The MF also decreased the content of silica fouling (silica and silicate) reached 22.4–46.3% by reducing the concentration of soluble silica and accelerating the flocculation settlement to form large size solid particles in BW. Furthermore, MF broke the synergistic interactions among calcium and silica fouling. In addition, the anti-fouling ability of permanent MF was higher by 12.3–35.1% than electric MF. Overall, these findings demonstrate that MF is an effective and chemical-free technology to control calcium-silica fouling in BWDS, and provide a new perspective for sustainable application of brackish water.