Removal of heavy metals from wastewater by biosorption using excess sludge

Activated sludge obtained from a paint industry wastewater treatment plant was found to be the most suitable among the others tested resulting in the highest biosorption capacity. Pre-treatment by 1 percent hydrogen peroxide solution was found to be superior to the other methods yielding the highest biosorption capacity.Effects of operating parameters on batch biosorption kinetics of copper ions onto pre-treated powdered waste sludge (PWS) were investigated. Batch isotherms of biosorption of Cu ions were investigated and the langmuir isotherm was found to fit the experimental data better than the other isotherms tested.Biosorption of Cu ions onto pre-treated powdered waste sludge (PWS) was also investigated using a fed-batch operated completely mixed reactor. Breakthrough curves describing variations of effluent copper ion concentrations with time were determined for different operating conditions.In order to investigate the adverse effects of Cu ions on performance of an activated sludge unit, synthetic wastewater containing Cu ion was treated in an activated sludge unit and COD, Cu, toxicity removals were investigated. Copper ion toxicity on COD removal performance of the activated sludge unit was partially eliminated by operation at high sludge ages (30 days) and HRT?s (25 hours).Copper ion toxicity onto activated sludge organisms was eliminated by addition of powdered waste sludge (PWS) to the feed wastewater for removal of Cu ions by biosorption before biological treatment. Box-Behnken experimental design method was used to investigate Cu, chemical oxygen demand (COD) and toxicity removal performance of the activated sludge unit under different operating conditions.