Improvement of Operational Mode of Counter-Current Dissolved Air Flotation Process

As a new dissolved air flotation (DAF), the countercurrent DAF (CCDAF) has been proved to overcome some limitations of the traditional co-current DAF. In this study, the operational mode of CCDAF process was improved to enhance the treatment efficiency by the step-recycle of dissolved air water. The experimental results indicated: the improved process could run steadily under higher hydraulic loading by comparison with the conventional one, when the recycle ratios were same in the two processes, the efficiency of the improved one was higher than that of the conventional one, under the appropriate operating parameters (hydraulic loading was below 17 m/h, recycle ratio was above 8%, the distance between the mobile nozzle and the inlet was within 70~90 cm, and the flow ratio of the mobile nozzle and the fixed one was within 2.5~3), the improved process had significant removal effects for turbidity and algae. So the improved CCDAF process is more advantageous than the conventional one in enhancing treatment efficiency and reducing operating cost.