Optimization of aeration conditions in the hybrid process of coagulation-ultrafiltration with air sparging

To optimize the aeration conditions in the hybrid process of coagulation-ultrafiltration with air sparging, a series of air flow rates under continuous and intermittent sparging were investigated. The water quality characteristics that surrounded membranes, bubble characteristics, fouling resistances, and energy consumption under different aeration conditions were analyzed. The results showed that increasing air flow rates generated more bubbles with a wider size distribution (i.e., more favorable hydrodynamic conditions). The turbidity and ultraviolet absorbance at 254 nm (UV 254 ) of the water that surrounded membranes were reduced as the air sparging kept flocs away from membranes. Thus, the membrane fouling was effectively mitigated by increasing air flow rates despite aeration modes. For a given air flow rate, less fouling was obtained under continuous sparging than the intermittent mode. With respect to intermittent sparging, the mode of 40-min aeration per hour more effectively alleviated membrane fouling than the mode of 30-min aeration per hour. Weighing the energy consumption and membrane fouling, optimum air flow rates under continuous mode were between 15 and 30 mL/min, and the optimal aeration condition for intermittent mode was set at the air flow rate of 30 mL/min under the mode of 40-min aeration per hour.