Abstract: This study investigated the floc aggregation, average floc size,
floc size variance and floc growth velocity when ferric chloride
(FeCl_3) and polyferric chloride (PFC) were used to treat
the simulated water samples. The factors including coagulant dose, ionic
strength and solution pH, which affect the floc aggregation, were studied.
Experiments were carried out in a bench-scale reactor using photometric
dispersion analyzer (PDA). Results showed that there were great differences
between the floc aggregation of PFC and FeCl_3. The average
floc size and floc growth velocity of PFC were much larger than those of
FeCl_3. Compared with FeCl_3, PFC gave a
better coagulation performance in wider range of pH, dosage and ionic strength.
It was also found that the coagulation efficiency of PFC did not depend on
average floc size but on floc growth velocity.
Keywords: coagulants, photometric dispersion analyzer (PDA), floc aggregation, water treatment