Helically Coiled Tube Flocculators for Water Clarification: Evaluation of Winding Diameter in Turbidity Removal Efficiency

Abstract

This paper aims to evaluate the turbidity removal efficiency of an alternative clarification system composed of a helically coiled tube flocculator (HCTF) coupled to a decantation system, to compare the change in process efficiency according to geometric changes of the unit, especially the winding diameter (D). The use of HCTFs has drawn the attention of the scientific community due to its high efficiency and its reduced detention time compared to other units commonly used for this purpose. Physical experimental tests were performed with two HCTFs with different winding diameters (5 and 30cm) and two flow rates (1 and 2L/min); results indicate that the changes obtained in the velocity profile with the change in the winding diameter of the unit promote changes in interaction between previously destabilized particles and thus changes in turbidity removal efficiency, with variations around 10%. The highest efficiencies of turbidity removal were obtained for the highest winding diameter, where lower velocity gradients are verified. High velocity gradient values ??verified in the unit with lower winding diameter may promote the breaking of previously formed flocs, reducing the efficiency of the treatment process. This result indicates that the winding diameter significantly influences the efficiency of water clarification system when using HCTFs and this parameter should be cautiously evaluated to ensure satisfactory process efficiency.