Ceramic membrane filtration as seawater RO pre-treatment: Influencing factors on the ceramic membrane flux and quality

Membrane filtration has been accepted as the preferred pre-treatment method in reverse osmosis (RO) processes in recent years. In this paper, a laboratory-scale ceramic membranes device, which has a potential to be used as pre-treatment for RO desalination, was employed to investigate the performance of ceramic membranes with different pore sizes and under different conditions. Ceramic membranes with pore sizes of 50, 200, 500, and 800nm were tested, and the effects of pore size, transmembrane pressure (TMP), coagulation method, and NaClO addition on the permeate flux and the permeate quality of ceramic membranes were studied. The results show that the pore size has an insignificant effect on the permeate flux of ceramic membranes but the coagulation method has a significant effect. Pore size and NaClO addition did not have significant effects on the turbidity of the ceramic membrane permeate, but they did affect the SDI₁₅ (Silt Density Index) values of the ceramic membrane permeate. A pilot test was executed using a pilot ceramic membrane device with an approximate capacity of 330m³/d. The TMP was stable with a constant flux of 150L/m²h and a cross-flow velocity of 0.015 m/s, and the turbidity and SDI₁₅ values were satisfactory for RO, suggesting that ceramic membranes can meet the demands of RO.