Appropriately used. computational fluid dynamics models are powerful tools to design and optimize primary settling tanks (PSTs). This paper uses a Fluent-based 3D model to identify the possible causes for underperformance of the circular PSTs at the Cali waste-water treatment plant. Colombia. https://www.diegojavierfares.com/mega-pick-SA439-EF75-5-x-7-Embroidery-Machine-Hoop-mega-pick/