Therefore, the flock formation
was promoted and the high removal efficiency was achieved. This
effect is due to the remaining CaCO3 acting as a coagulant aid by
forming larger
flocks which provide a relatively shorter settling
time for the removal of DOC [33–35].
Bentonite was used as a coagulant aid to investigate the effect of
particles in order to clarify the role of CaCO3 on coagulation of HA
using PAC. PAC coagulated both positively charged CaCO3 and
negatively charged bentonite suspended in distilled water. CaCO3
added into HA solution coagulated with PAC formed large
flocks
and precipitated rapidly. On the other hand,
flocculation did not
occur for bentonite in the existing HA, and therefore, no