Flocculation of Organic Matter and Aluminum in Water Using Chitosan-Inorganic Coagulant

Chitosan can be a potential substitute for aluminum salts and synthetic polyelectrolytes in water treatment because it can: (1) avoid the health effects from residual aluminum (III) and synthetic polymers; (2) produce biodegradable sludge; and (3) reuse the crab shell. In this study, the chitosan flocculation characteristics in water were studied firstly, and then the combined flocculation of chitosan and inorganic flocculant is tested. The results show that the chitosan has favourable coagulation behavior. But the optimum dosage of chitosan removing turbidity and organic matter is different by using chitosan alone. However, the combined flocculation can obviously promote their each coagulant behavior and remarkably enhance the effect of organic matter removal. More importance, the optimal effect of turbidity and organic matter removal can be achieved at the same time. Comparing the effect of three inorganic coagulants combined with chitosan, the effect of chitosan combined with polymeric aluminium-ferric is best, under optimum conditions, the rate of removing turbidity, COD_Mn and UV₂₅₄ achieved 97%, 44% and 55% respectively. And whether chitosan combining with inorganic flocculation or not, on the best conditions, the residual aluminum concentration is less than the examination methods limit in effluent water.