Membrane fouling control by Ca during coagulation-ultrafiltration process for algal-rich water treatment.

Seasonal algal bloom, a water supply issue worldwide, can be efficiently solved by membrane technology. However, membranes typically suffer from serious fouling, which hinders the wide application of this technology. In this study, the feasibility of adding Ca to control membrane fouling in coagulation-membrane treatment of algal-rich water was investigated. According to the results obtained, the normalized membrane flux decreased by a lower extent upon increasing the concentration of Ca from 0 to 10 mmol/L. Simultaneously, the floc particle size increased significantly with the concentration of Ca, which leads to a lower hydraulic resistance. The coagulation performance is also enhanced with the concentration of Ca, inducing a slight osmotic pressure-induced resistance. The formation of Ca coagulation flocs resulted in a looser, thin, and permeable cake layer on the membrane surface. This cake layer rejected organic pollutants and could be easily removed by physical and chemical cleaning treatments, as revealed by scanning electron microscopy images. The hydraulic irreversible membrane resistance was significantly reduced upon addition of Ca. All these findings suggest that the addition of Ca may provide a simple-operation, cost-effective, and environmentally friendly technology for controlling membrane fouling during coagulation-membrane process for algal-rich water treatment.