Biosorption Capacity of Activated Sludge Sand Bed for Removal of Copper from Treated Wastewater

In this paper, the biosorption capacity of activated sludge sand bed was investigated for copper removal from wastewater. A sand bed consisting of three layers was used for the study: (1) filter gravel with a diameter of 2 to 3 mm, (2) a biological part inoculated with 200 ml of flocculent activated sludge with a dry weight of 5 kg/$m^3$, (3) filter sand with a grain diameter of about 3 mm. The filter was fed with model wastewater prepared with sodium acetate, potassium nitrate, ammonium chloride, and potassium dihydrogen phosphate I and II basic. The source of Cu ions in the wastewater was $CuSO_4$. The model wastewater used in this study was collected every 24 hours. The experiment was terminated when the concentration of Cu in the treated wastewater sample was equal to that in the treated wastewater. Such a phenomenon was indicative of the depletion of the sorption capacity of the tested bed, which was observed after 26 days. The concentration of copper in raw and effluent from the bed was studied using atomic absorption spectroscopy (ASA) in samples mineralized in nitric acid ($HNO_3$) with the addition of perhydrol ($H_2O_2$). Two equilibrium models, Langmuir and Freudlich, were analyzed to study the absorption isotherms.