Impact of Chemical Coagulants for Oscillatoria sp. Removal from Raw Water on Chemical Coagulation Process

Growing Oscillatoria sp. in freshwater causes several poisoning episodes of domestic livestock animal and human. The chemical coagulation of raw water using chemical coagulants is very simple and requiring less investment cost on equipment. These experiments used alum and PACl (Polyaluminium chloride) with alum as chemical coagulants for Oscillatoria sp. removal. The Oscillatoria sp. was prepared from Molecular and Cell Laboratory of Thailand Institute of Scientific and Technological Research and grown in BG-11 medium. The samples of treated water use chemical coagulation test to verify their efficiency of Oscillatoria sp. cells removal from the synthetic raw water. The results show that the chemical coagulation using alum coagulant and PACl with alum coagulants produces a high efficiency in Oscillatoria sp. removal. However, the PACl with alum coagulants provided the best Oscillatoria sp. removal efficiency and the low amount of chemical coagulants for Oscillatoria sp. removal process. The PACl with alum doses at 1:10 by weight, provides the best Oscillatoria sp. removal efficiency at 97%. While, the best Oscillatoria sp. removal efficiency of alum dose at 90 mg/L, is 98%. It can be concluded that the PACl with alum doses as the combined chemical coagulant provided the highest efficiency at the lowest amount of chemical coagulants used.