ATCH biosorption experiments were carried out for the removal of four dyes; Drimarene yellow CL4R (Y), Drimarene blue K2RL (B), Congo Red (CR) and Malachite Green (MG) from their aqueous solutions using two algal biomasses namely Gelidium latifolium (Grev.) Bornet et Thuret (red alga) and Ulva lactuca Linnaeus (green alga). The optimum conditions were applied in the treatment of eleven coloured industrial effluents from Borg El-Arab region, Egypt. Some modifications of the algal surface due to the bio-sorption process were noticed using SEM such as protuberance, wrinkle, shrinkage, stickiness, rupture and roughness. The bio-sorption process led to several band shifts that were detected using FTIR revealing the participation of C-N-S, alcoholic C-O, carboxylic C-O, carboxylic C=O, NH and OH groups in dyes bio-sorption. This bio-sorption was nonspontaneous, endothermic and chemical in nature. Freundlich isotherm model fitted slightly better than the Langmuir model indicating multilayer coverage (heterogeneous sorption). Utilization of C 2 H 5 OH for Y and B; NH 4 OH and HNO 3 for CR and MG, respectively was showed the most desorption efficiency for 4 reuse cycles of sorption-desorption. However, desorption and resorption efficiencies decrease with increasing the reusability cycle number. Ulva lactuca has shown much better dyes bio-sorption efficiency particularly with solid/liquid ratio: 1/1000 g/mL, initial dye concentration: 400 mg/L, temperature: 40° C, contact time: 1 hour, pH: 1, 2, 8 and 7 for Y, B, CR and MG, respectively. The applied decolourization of coloured samples reached 97.46 %.