Overview of Biological Technologies for Azo Dye removal Fundamental of Aerobic and Anaerobic Processes in Dye Wastewater Aerobic Biological Units in Dye Removal Anaerobic Processes in Dye Removal Activated Sludge: Conventional Dye Treatment Technique The role of moving bed bioreactor (MBBR) in dye removal Up-flow Anaerobic Sludge Blanket Reactors in Dye Removal: Mechanisms, Influence Factors, and Performance