Numerical Investigation of the Effect of Bar Design on the Retention Efficiency of Wastewater Bar Screens

Abstract

Mechanical bar screens serve as the initial treatment stage used to catch insoluble and coarse debris from wastewater flow. They are essential equipment that ensures the protection and efficient operation of downstream facilities. Different parameters affect the performance of bar screens, including particle size, flow hydraulics, and screen design. Most previous studies have primarily focused on bar screens with rectangular bars and single-phase flow. However, investigating different bar shapes with the presence of waste debris as a second phase is crucial for achieving the optimal design and accurately predicting a bar screen’s efficiency. Therefore, four bar cross-section shapes were examined using 3D simulations of two-phase flow (water and particles). The discrete phase model (DPM) in ANSYS Fluent CFD software was used to represent waste particles in a Lagrangian framework and to evaluate their retention efficiency. The numerical results, validated by a previous study of a wastewater bar screen, indicate that the traditional rectangular bar shape traps a higher rate of debris but results in higher pressure losses. Alternative bar shapes, such as rounded, streamlined, and teardrop cross-sections, have been studied for design improvements. The improved teardrop shape presents significant effectiveness, offering a better balance between pressure loss reduction and enhanced particle separation efficiency. Based on this study, further investigations coupling CFD techniques with the particle tracking method can be carried out for the optimal design of other filtration equipment.