Study on the Effect of Bubbles on the Removal Efficiency of a Helical Tube Flocculator

The tubular flocculation reactor is a new and efficient device for treating algae-containing wastewater. The introduction of bubbles during the reaction process can effectively shorten the time required for floc separation. However, the impact of bubbles on floc formation and removal in the tubular flocculation reactor is not well understood. To further clarify the effect of bubbles on the reactor's operation, this study employed a uniform experimental design, varying the flow rate, chemical dosage, bubble reaction distance, and bubble injection rate in the reactor to examine the influence of bubbles under different operating conditions. The results indicated that as the bubble reaction distance increased from 0 m to 7.6 m, the removal efficiency increased from 60% to 70%, the floc size increased from 160 mu m to 165 mu m, and the fractal dimension decreased from 2.1 to 1.9. When the bubble volume increased from 5% to 30%, the removal efficiency increased from 50% to 80%. Under constant bubble conditions, the rising speed of the flocs increased from 0.4 mm<middle dot>s-1 to 1.2 mm<middle dot>s-1, while the removal efficiency increased from 30% to 90%. A logarithmic correlation was observed between the rising speed and removal efficiency. A linear relationship was found between the floc rising speed and the floc size, with floc size increasing from 200 mu m to 800 mu m and the rising speed increasing from 0.4 mm<middle dot>s-1 to 2.3 mm<middle dot>s-1. An exponential relationship was found between the fractal dimension and the rising speed, with the rising speed decreasing from 2.3 mm<middle dot>s-1 to 0.4 mm<middle dot>s-1, while the fractal dimension increased from 1.93 to 2.02.