Comparison of four kinds of coagulants for the removal of picophytoplankton.

The purpose of this study was to investigate the efficiency of the coagulation process for the removal of picophytoplankton from drinking water and, in addition, to investigate the performance of simple coagulants such as alum and ferric chloride, and polymer coagulants such as PAC and PSI, in picophytoplankton removal. Two simple coagulants such as alum (Al₂(SO₄)₃·16H₂O) and ferric chloride (FeCl₃·6H₂O) and two polymer coagulants such as poly-silicate iron (PSI) and poly-aluminum chloride (PAC) were used in both raw water including picophytoplankton and synthetic water samples prepared by Synechococcus sp. Analyses included a picophytoplankton count, an assessment of the turbidity, dissolved organic carbon, UV₂₅₄, and zeta potential and the settling time measurements. The removal efficiency of picophytoplankton during the coagulation-flocculation-sedimentation process was determined using simple and polymer coagulants. Water samples with lower coagulation pH had better picophytoplankton removal in coagulation-flocculation-sedimentation. The results indicate that even low coagulant doses of PSI in both raw water and artificial water performs better than the other three types of coagulants in terms of picophytoplankton, turbidity, UV₂₅₄, and DOC removal. [ABSTRACT FROM AUTHOR]