17
Turbidity Removal by Polyelectrolytes as
Flocculant Aids in Flocculation with Aluminium
Salts
N. Narkisl, B. Ghattas 1 , M. Rebhun 1 , and A. Rubin2
lEnvironmental and Water Resources Engineering, Technion-Israel Institute 0/
Technology, Haifa 32000, Israel. e-mail: cvrnava@tx.technion.ac.il
Tel: +972-4-8293925, Fax: +972-4-8228898
2 Water Resources Center, College o/Engineering, The Ohio State University,
Columbus, Ohio, USA
Abstract
The effect of the combination of aluminium nitrate and cationic polyelectrolytes,
based on quaternary amines homopolymers and acrylamide copolymers, with
various charge densities on the flocculation of Ca-montmorillonite clay mineral
suspension was investigated. A stable clay suspension was flocculated with each
of the cationic polymers and the aluminium nitrate alone and in a combination of
both types of flocculants, in which the Al(III) salt was added first. All the cationic
polymers improved the flocculation of aluminium nitrate at the underdose and at
the range of good clarification, with a more efficient turbidity removal and in its
overall characteristics. The copolymers were also effective at the beginning of the
overdose range of the Al (III) flocculant. The mechanism of the flocculation of the
polymeric flocculants in combination with Al (III) salts is explained as an
adsorption and bridging. The results of this research can be implemented in
operational recommendations, such as the type of polymer to be used, and the
concentration ratios of each kind of polymer and the Al (III) salt in the specific
combination.
Introduction
Improved flocculation processes are needed whenever removal of turbidity is
required from natural or renovated waters. The combination of inorganic
flocculants such as aluminium or ferric salts and synthetic polyelectrolytes and
polymers is used frequently in water and wastewater treatment (Roberts et al.
1974; James and Q'Melia 1982; Letterman et al. 1982). Usually the polymer type
H. Rubin / P. Nachtnebel / J. Fuerst / U. Shamir
Preserving the Quality of Our Water Resources
© Springer-Verlag Berlin Heidelberg 2002
Turbidity Removal by Polyelectrolytes as
Flocculant Aids in Flocculation with Aluminium
Salts
N. Narkisl, B. Ghattas 1 , M. Rebhun 1 , and A. Rubin2
lEnvironmental and Water Resources Engineering, Technion-Israel Institute 0/
Technology, Haifa 32000, Israel. e-mail: cvrnava@tx.technion.ac.il
Tel: +972-4-8293925, Fax: +972-4-8228898
2 Water Resources Center, College o/Engineering, The Ohio State University,
Columbus, Ohio, USA
Abstract
The effect of the combination of aluminium nitrate and cationic polyelectrolytes,
based on quaternary amines homopolymers and acrylamide copolymers, with
various charge densities on the flocculation of Ca-montmorillonite clay mineral
suspension was investigated. A stable clay suspension was flocculated with each
of the cationic polymers and the aluminium nitrate alone and in a combination of
both types of flocculants, in which the Al(III) salt was added first. All the cationic
polymers improved the flocculation of aluminium nitrate at the underdose and at
the range of good clarification, with a more efficient turbidity removal and in its
overall characteristics. The copolymers were also effective at the beginning of the
overdose range of the Al (III) flocculant. The mechanism of the flocculation of the
polymeric flocculants in combination with Al (III) salts is explained as an
adsorption and bridging. The results of this research can be implemented in
operational recommendations, such as the type of polymer to be used, and the
concentration ratios of each kind of polymer and the Al (III) salt in the specific
combination.
Introduction
Improved flocculation processes are needed whenever removal of turbidity is
required from natural or renovated waters. The combination of inorganic
flocculants such as aluminium or ferric salts and synthetic polyelectrolytes and
polymers is used frequently in water and wastewater treatment (Roberts et al.
1974; James and Q'Melia 1982; Letterman et al. 1982). Usually the polymer type
H. Rubin / P. Nachtnebel / J. Fuerst / U. Shamir
Preserving the Quality of Our Water Resources
© Springer-Verlag Berlin Heidelberg 2002