Taken into consideration of PAC as a proper coagulant, further
investigation was carried out by removing HA through coagulation
using PAC with CaCO3 as neutralizer and coagulant agent. The
comparison with the existing techniques are shown in Fig. 2 and it
clearly indicates that PAC is even able to remove HA at low dosage.
The removal ratio was maintained more than 95% when the PAC
dosage was more than 20 mg/L. This removal ratio is higher than
the case of using NaOH as an alkaline chemical. Since CaCO3
behaves as a coagulant reagent, the sedimentation velocity was
significantly high and the SV was reduced about half compared
with the case of using NaOH as a neutralizer. Therefore, the
utilization of CaCO3 combination with coagulation method by PAC
is efficient in removing HA because it is able to perform both as
alkaline chemical and as a coagulant agent about the same time.