Effects of Chlorination on Algae Coagulation Efficiency and Formation of Disinfection By-Products
Raw water quality is deteriorated because of the excessive development of industries, which promotes eutrophication and causes the blooming of algae in the reservoirs. Eutrophication makes the treatment of drinking water difficult. Algae cause uncomfortable taste and odor, clog the filter and penetrate the filter, leading to the deterioration of drinking water quality. In addition, Algae and its extracellular products are precursors of disinfection by-products. The goal of this study was to evaluate the effects of chlorination on algae and the subsequent coagulation. Algae used in this study was a green alga (Chlorella sp.). The coagulants used were aluminum sulfate and polyaluminum chlorides. A high significant correlation was found between the removal efficiency of algae and the formation of dissolved organic compounds (DOC) on chlorination. Chlorination simultaneously produces the harmful trichloromethane compounds. With coagulation coupled to sedimentation, it can obviously remove the algae and precursor to trichloromethanes, but the DOC was difficult to remove by coagulation. On the other hand, prechlorination reduced the efficiency of algae coagulation, but no effect on the removal of the precursor of trichloromethanes. Algae removal decreased with the dosage of chlorine. Satisfactory removal occurred at overdosing only. The order of chemical dosing affected the removable efficiency of algae. Pre-chlorination had a detrimental effect on algae removal. Simultaneous chlorination and coagulation resulted in poor algae removal.