The efficiency of biological sludge on hexavalent chromium removal from aqueous solution

Out of different techniques for chromium (Cr) removal, biological treatment has a special status. This study was conducted to determine the efficacy of biological sludge on hexavalent Cr (VI) removal from aqueous solutions. In this experimental study, the required sludge was collected from municipal sewage refinery after aeration basin and introduced into the reactor and Cr and nutrients were added to it. The effect of dissolved oxygen (DO), Cr initial concentration, pH, temperature, glucose concentration, and contact time on chromium removal rate was evaluated. At each step, the samples withdrawn from the reactor were filtered and Cr (VI) level was measured using HACH Company instructions and spectrophotometry. The findings of this study showed that at 2 mg/L DO, 80 mg/L Cr initial concentration, 5000 mg/L sludge concentration, pH= 3, 30°C temperature, 250 mg/L introduced glucose concentration, and 24 h contact time, about 97.5 % of Cr (VI) was removed. As DO, pH, and the introduced glucose concentration decreased and the initial sludge concentration increased, temperature and contact time of Cr removal efficiency increased. The results of this study showed that use of the activated sludge of sewage refinery could be used for Cr removal with regards to environmental aspects.