[en] Highlights: ► Phytoremediation of radioactive wastes containing ¹³⁷Cs and ⁶⁰Co radionuclides. ► Using water hyacinth for radioactive waste treatment. ► Bioaccumulation of radionuclides from radioactive waste streams. ► Factors affecting bioaccumulation of ¹³⁷Cs and ⁶⁰Co using floating plants. - Abstract: Phytoremediation is based on the capability of plants to remove hazardous contaminants present in the environment. This study aimed to demonstrate some factors controlling the phytoremediation efficiency of live floating plant, water hyacinth (Eichhornia crassipes), towards the effluents contaminated with ¹³⁷Cs and/or ⁶⁰Co. Cesium has unknown vital biological role for plant while cobalt is one of the essential trace elements required for plant. The main idea of this work i.e. using undesirable species, water hyacinth, in purification of radiocontaminated aqueous solutions has been receiving much attention. The controlling factors such as radioactivity concentration, pH values, the amount of biomass and the light were studied. The uptake rate of radiocesium from the simulated waste solution is inversely proportional to the initial activity content and directly proportional to the increase in mass of plant and sunlight exposure. A spiked solution of pH ≈ 4.9 was found to be the suitable medium for the treatment process. The uptake efficiency of ¹³⁷Cs present with ⁶⁰Co in mixed solution was higher than if it was present separately. On the contrary, uptake of ⁶⁰Co is affected negatively by the presence of ¹³⁷Cs in their mixed solution. Sunlight is the most required factor for the plant vitality and radiation resistance. The results of the present study indicated that water hyacinth may be a potential candidate plant of high concentration ratios (CR) for phytoremediation of radionuclides such as ¹³⁷Cs and ⁶⁰Co.