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DOI : ,    Vol.3, No.2, 31 ~ 43, 1995
Title
Influences of Molecular Weight and Si Component of PACS on Coagulation and Sedimentation in Drinking Water Treatment
곽종운Jong Woon Kwak
Abstract
A newly developed coagulant of Si-inserted poly aluminium chloride silicate(PACS) which is characterized to higher molecular weight and Si insertion was demonstrated through laboratory and full scale tests to be resulted in the superior turbidity removal, less dosage rate and higher organics removal in comparison with the existing coagulants. The dosage rate of PACS in volume was about half of poly aluminium chloride in removing about 90% turbidity at a given condition. With PACS containing Si, the sedimentation rate after coagulation was faster than one obtained from poly aluminium chloride due to its enhanced crosslinking effect coming from Si linked within the polynuclear Al backbone. Intensive turbulence when the coagulant is mixed with the raw water was of larger importance for obtaining a lower turbidity. In the process of deactivation of aluminium, a inhomogeneous distribution of chemicals in water to be treated gave the lack of optimal turbidity removal which leads to the heterogeneous settling rates. The poorly reduced turbidity seemed to be improved by selecting a optimal dosing point or by increasing the coagulant dose. In residual Al, the particulate aluminium was demonstrated to be minimized by decreasing the remaining flocs after treatment, suggesting that their surfaces could be favorable to adsorbe Al species.
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