Rapid increases in world population and industrialization have seriously contributed to heavy metals pollution in aquatic/ terrestrial ecosystems. Among heavy metals, chromium pollution has taken more attention in recent years due to its harmful effects to living organisms and ecosystems. The two common stable species of chromium are trivalent Cr (III) and hexavalent Cr (VI) that found mostly in wastewater from electroplating industries, leather tanning, wood preservation and dyes, steel, alloy, glass, textile industries, film and photography. Different technologies such as chemical precipitation, ion exchange, membrane technologies, reverse osmosis and adsorption were used to remove heavy metals from aqueous solution. In recent years, more interests have been focused on biosorption as an economic and efficient method to remove metals ions. Biosorption is a method which natural materials with different biological origin including bacteria, fungi, yeast, algae, agricultural and industrial wastes were used as biosorbent. In this study, dry biomass of green microalgae Scenedesmus quadricauda (Chlorophyta) was used to remove Cr (III) and Cr (VI) from aqueous solutions and industrial wastewater by batch and column experiments. Some of physical, chemical and morphological properties of microalgae biosorbent were determined by the elemental analysis, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). In addition, the parameters influencing on biosorption including equilibrium time, pH, metal solution initial concentration, amount of adsorbent were investigated. Results showed that equilibrium time for removal of Cr (III, VI) is 120 min. The adsorption kinetics had better fit by the pseudo-second-order kinetics for both species of Cr (III, VI). The maximum adsorption of Cr (III) and Cr (VI) were occurred at pH=6 and pH=1, respectively. The comparison of results illustrated that Cr (III) adsorption was fitted better by Redlich-Peterson and Langmuir isotherm models than that the Freundlich model. The adsorption of Cr (IV) was fitted better by Redlich-Peterson and Freundlich isotherm models. The highest adsorption of Cr (III) and Cr (VI) were predicted 58.47 and 46.51 mg/g according to Langmuir equation, respectively. When the amount of microalgae biosorbent increased from 0.2 to 10 g/L at 100 mg/L of Cr (III, VI), the adsorption percentage were increased from 30.03 to 96.40% for Cr (III) and 7.67 to 64.12% for Cr (IV). In the column experiments sorption performance was 30 % for Cr (III) ions (63.3 mg/g) and 13% for Cr (VI) ions (25.5 mg/g). Chromium desorption was possible using HNO 3 and NaOH. The higher ability for desorption were obtained by 0.1 M of HNO 3 for Cr (III) (85%) and 0.1 M of NaOH for Cr (VI) (60%). Keywords : Chromium, Biosorption, Microalgae, Scenedesmus quadricauda , Adsorption isotherms