Effects of Different Coagulants on Coagulation Process for Removal of Microcystis aeruginosa

The effects of different coagulants on coagulation process for algal removal were investigated with the laboratory scale to obtain data for their influence to drinking water treatment processes. Aluminum sulfate, which is the most commonly used for coagulation process in the world, and two other polymer coagulants, poly aluminum chloride and poly aluminum chloride silicate, were used to check coagulation efficiencies for algae removal. Microcystis aeruginosa, one of cyanobacteria and main species during waterbloom in worldwide, were selected and prepared their cells in each growth phase for coagulation tests. Coagulation inhibitions were shown for cells in log-growth phase as well as stationary phase in which periods algae cells might be most active, especially, when using poly aluminum chloride and poly aluminum chloride silicate. On the other hand, coagulation efficiencies were high with all coagulants for cells in lag phase as well as death phase. As result of the research, although polymer coagulants are generally known as better ones than aluminum sulfate, aluminum sulfate should be used during waterbloom rather than polymer coagulants such as poly aluminum chloride and poly aluminum chloride silicate since the most of algae cells during waterbloom may be in the log-growth phase and/or lag phase.