The coagulants of poly-aluminum-chloride (PAC), poly-aluminum-silicate-chloride (PASiC) and poly-aluminum-ferric-silicate-chloride (PAFSiC)
were prepared in this study to evaluate their coagulation efficiencies and mechanisms in synthetic low-turbidity and low-alkalinity water
containing organic matter. The experimental results show that PASiC and PAFSiC could remove the kaolin turbidity of the synthetic water with or
without salicylic acid present. On the other hand, when the synthetic water contained both kaolin and humic acid in low turbidity and alkalinity,
PAC would remove the turbidity but charge reversal of the colloidal particles would occur easily. Also, effective coagulation was limited to a very
narrow dosage range. Conversely, the dosage range for the effective coagulation of both PASiC and PAFSiC was wider, although a higher dosage
was required to remove the turbidity of wastewater. Therefore, the effective removal of turbidity was not only related to the kind of coagulant, but
also to the types of organic matter. The coagulants PASiC and PAFSiC, particularly, proved themselves to be superior to the PAC in the treatment
of low-turbidity water