TY - JOUR
T1 - Influence of velocity gradient and rapid mixing time on flocs formed by polysilica iron (PSI) and polyaluminum chloride (PACl)
AU - Aktas, Tugrul Selami
AU - Fujibayashi, Megumu
AU - Maruo, Chikako
AU - Nomura, Munehiro
AU - Nishimura, Osamu
N1 - Funding Information:
This research was supported by the Ecological Engineering Laboratory. Thanks are extended to Dr. O. Nishimura for his editing of the text and to the reviewers for their suggestions on how to improve this paper.
PY - 2013
Y1 - 2013
N2 - The aim of this investigation was to evaluate the effect of different velocity gradient and rapid mixing time on coagulation and floc properties, using polysilica iron (PSI) and polyaluminum chloride (PACl) with different rapid mixing speeds and times. The growth, breakage, and re-growth of flocs were monitored by a particle-size analyzer during the rapid mixing, in order to determine the underlying mechanisms. For PSI and PACl, three different zones were found to depending on the G value in the coagulation process. At low G values (G < 546 s-1 for PSI flocs and G < 390 s-1 for PACl flocs), the aggregation dominated over breakup. At mean G values (G = 546 s-1 for PSI flocs and G = 390 s-1 for PACl flocs), floc formation was maximized with the largest flocs produced at the lowest residual turbidity. For large G values (G > 546 s-1 for PSI flocs and G > 390 s-1 for PACl flocs), breakup dominated over floc formation. Broken flocs did not fully re-grow after breakage, probably as a result of a change in the floc surface properties arising from the rupture of bonds within the hydroxide precipitate. A rapid mixing time of 60 s led to maximum floc formation. In addition, PSI flocs were more durable to high than PACl.
AB - The aim of this investigation was to evaluate the effect of different velocity gradient and rapid mixing time on coagulation and floc properties, using polysilica iron (PSI) and polyaluminum chloride (PACl) with different rapid mixing speeds and times. The growth, breakage, and re-growth of flocs were monitored by a particle-size analyzer during the rapid mixing, in order to determine the underlying mechanisms. For PSI and PACl, three different zones were found to depending on the G value in the coagulation process. At low G values (G < 546 s-1 for PSI flocs and G < 390 s-1 for PACl flocs), the aggregation dominated over breakup. At mean G values (G = 546 s-1 for PSI flocs and G = 390 s-1 for PACl flocs), floc formation was maximized with the largest flocs produced at the lowest residual turbidity. For large G values (G > 546 s-1 for PSI flocs and G > 390 s-1 for PACl flocs), breakup dominated over floc formation. Broken flocs did not fully re-grow after breakage, probably as a result of a change in the floc surface properties arising from the rupture of bonds within the hydroxide precipitate. A rapid mixing time of 60 s led to maximum floc formation. In addition, PSI flocs were more durable to high than PACl.
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U2 - 10.1080/19443994.2012.751883
DO - 10.1080/19443994.2012.751883
M3 - Article
AN - SCOPUS:84879683562
VL - 51
SP - 4729
EP - 4735
JO - Desalination and Water Treatment
JF - Desalination and Water Treatment
SN - 1944-3994
IS - 22-24
ER -