COAGULATION-FLOCCULATION PROCESSES IN WATER / WASTEWATER TREATMENT : THE APPLICATION OF NEW GENERATION OF CHEMICAL REAGENTS

The aim of this paper is to provide an overall description of coagulation-flocculation process and its applications in water and wastewater treatment. The significance of coagulation – flocculation in the area of water and wastewater treatment is reviewed and evaluated, emphasizing on the series of applications employed, including destabilization of colloids, removal of inorganic and organic matter (particulate and/or dissolved), removal of metals and anions (arsenic, phosphate etc), as well as removal of pathogen microorganisms. Furthermore, the latest developments in the coagulation field, regarding the evolution of the coagulation reagents, are also under investigation. The development of simple pre-polymerized coagulants (i.e. polyaluminium chloride,) seems no longer to be sufficient enough. The need for more effective coagulants has lead to the development of new coagulant categories, via the introduction of various additives in the structure of pre-polymerized coagulants. The first effort was reported 15 years ago, suggesting the use of silica in the form of polysilicates for such a purpose. Nowadays, the range of additives has expanded, including organic compounds, such as anionic, cationic or non-ionic polyelectrolytes, leading to new composite coagulants. Overall, it is evident that the tendency in the coagulation field nowadays is the production of modified composite coagulants, which they are becoming more and more complicated, regarding their composition, but also more effective, when compared with the traditionally applied reagents. Key-Words: Coagulation; flocculation; composite coagulants; inorganic additives; organic additives.

[1]  A. Zouboulis,et al.  The application of novel coagulant reagent (polyaluminium silicate chloride) for the post-treatment of landfill leachates. , 2008, Chemosphere.

[2]  D. Parker,et al.  Formation of the "Al13" tridecameric aluminum polycation under diverse synthesis conditions , 1992 .

[3]  H. Tang,et al.  Preparation and characterisation of polyaluminium silicate chloride coagulant , 2003, Environmental technology.

[4]  M. Dietzel.  Dissolution of silicates and the stability of polysilicic acid , 2000 .

[5]  B. Gao,et al.  Color removal from simulated dye water and actual textile wastewater using a composite coagulant prepared by ployferric chloride and polydimethyldiallylammonium chloride , 2007 .

[6]  J. Gregory,et al.  Coagulation by hydrolysing metal salts , 2003 .

[7]  S. Chan.  A review on solubility and polymerization of silica , 1989 .

[8]  M. Muhammed,et al.  Novel synthesis of Al13-cluster based alumina materials , 1999 .

[9]  A. Zouboulis,et al.  Polyaluminium silicate chloride - a systematic study for the preparation and application of an efficient coagulant for water or wastewater treatment. , 2009, Journal of hazardous materials.

[10]  B. Gao,et al.  The chemical species distribution and transformation of polyaluminum silicate chloride coagulant. , 2002, Chemosphere.

[11]  A. Stamou,et al.  Inorganic pre-polymerized coagulants: current status and future trends. , 2007 .

[12]  B. Gao,et al.  Evaluation of aluminum-silicate polymer composite as a coagulant for water treatment. , 2002, Water research.

[13]  Norihito Tambo,et al.  Characteristics of Metal-Polysilicate Coagulants , 1991 .

[14]  David H. Bache,et al.  Flocs in Water Treatment , 2007 .

[15]  Z. Jia,et al.  Synthesis of Polyaluminum Chloride with a Membrane Reactor: Operating Parameter Effects and Reaction Pathways , 2004 .

[16]  G. Amy,et al.  Determining the effectiveness of conventional and alternative coagulants through effective characterization schemes. , 2004, Chemosphere.

[17]  Werner Stumm,et al.  Formulation of polysilicates as determined by coagulation effects , 1967 .

[18]  B. Gao,et al.  The Chemical Species Distribution of Aluminum in Composite Flocculants Prepared from Polyaluminum Chloride (PAC) and Polydimethyldiallylammonium Chloride (PDMDAAC) , 2005 .

[19]  F. Chi,et al.  Evaluating the Coagulants of Polyaluminum Silicate Chlorides on Turbidity Removal , 2006 .

[20]  A. Zouboulis,et al.  Comparable evaluation of various commercially available aluminium‐based coagulants for the treatment of surface water and for the post‐treatment of urban wastewater , 2005 .