Decolorization and COD removal of yeast wastewater by coagulation process using poly-aluminum chloride

摘要

An experimental study was conducted to test the effectiveness of coagulation using polyaluminum chloride (PAC) to reduce the color and COD of the secondary effluent of yeast wastewater. The coagulant dose, pH and mixing condition of coagulation were optimized. Polyacrylamide (PAM) as coagulant aids for coagulation performance was also studied. The optimal conditions corresponded to pH 6 and a dose of PAC of 6 g/l with 69.8% COD removal and 91.7% color removal. The recommended dose, however, is 4 g/l at pH of 6, with 68.7% COD removal and 90.35% color removal, which is cheaper in practical use. The mechanism of coagulation with PAC is discussed. Sweep coagulation is proposed as the dominant mechanism according to zeta potential measurement.