A new inorganic polymer coagulant of polysilicato-iron (PSI) was evaluated as an alternative to aluminium coagulant. In this study, long-term performance of PSI on coagulation, sedimentation and filtration for phytoplankton, turbidity and DOC in raw water from a eutrophic reservoir were evaluated by a pilot plant in comparison with PAC. PSI was found to be more effective in the coagulation and removal in comparison with PAC. The flocs formed by PSI could be settled more quickly than those by PAC and, therefore, the size of sedimentation facilities can be reduced by the introduction of PSI. PSI was able to produce filtered water with low turbidity and colour. The number of phytoplankton cells in the filtered water of PSI was smaller than that of PAC. Most of the residual flocs in the settled water were trapped in the coarse layer of anthracite, and this result suggested that a higher rate of filtration can be achieved with PSI by increasing particle size of the filter media.

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