Plenary Speech:

Coagulation-Flocculation Processes in Water/Wastewater Treatment: The Application of New Generation of Chemical Reagents
 

Professor Anastasios Zouboulis
Professor of Chemical & Environmental Technology
Division of Chemical Technology (Lab. Of General & Inorg. Chem. Techn.), Department of Chemistry, Faculty of Sciences,
Aristotle University of Thessaloniki
(Box 116), GR-541 24 Thessaloniki,
GREECE

TEL.: (+30)-2310-99.7794 (direct)
FAX: (+30)-2310-206.138 (central) or 2310-99.7759 (direct)

E-mail: zoubouli@chem.auth.gr

 

Abstract: Drinking water of high quality is essential for human beings. Additionally, the discharge criteria of wastewaters are becoming stricter, according to the new legislation in force, in order to prevent environmental pollution and/or degradation of drinking water sources. A very important step of water and wastewater treatment is coagulation-flocculation, which is widely used, due to its simplicity and cost-effectiveness. Regardless of the nature of the treated sample (various types of water or wastewater) and the overall applied treatment scheme, coagulation-flocculation is usually included, either as pre- or post-treatment step. The efficiency of coagulation-flocculation strongly affects the overall treatment performance; hence the increase of the efficiency of coagulation stage seems to be a key factor for the improvement of the overall treatment efficiency.
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 or wastewater treatment is reviewed and evaluated, emphasizing the several 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 pathogenic microorganisms. Furthermore, the latest developments in the coagulation field, regarding the evolution of the coagulation reagents is also under investigation. The development of the simple pre-polymerized coagulants (i.e. polyaluminium chloride, polyferric sulphate) 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 the pre-polymerized coagulants. The first effort was reported 15 years ago, suggesting the use of silica in the form of poly-silicates 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 coagulant reagents. Overall, it is evident that the tendency in the coagulation field nowadays is the production of modified composite chemical agents, which they are becoming more and more complicated, regarding their composition, although they are simpler in their applications.
 

Brief Biography of the Speaker:
Dr. Anastasios Zouboulis is Professor of Chemical & Environmental Technology, Department of Chemistry, Aristotle University of Thessaloniki and has a great experience in the field of water and wastewater treatment technologies, wastewater management, reclamation and reuse. He is author/co-author of more than 150 papers, published in scientific journals and of more than 100 papers published in the proceedings of national & International conferences. He has supervised 5 Ph.D. and 10 M.Sc. Theses and more than 50 Diploma theses. He has participated in more than 40 national and international research and demonstration projects, funded by E.U. and from local sources (ministries, industries, companies etc.), while he was Scientific Responsible in the 25 of them, regarding mainly with the fields of wastewater treatment processes, environmental biotechnology, as well as the treatment of industrial solid toxic wastes by the application of appropriate stabilization methods. His international reputation was recognised by his election as (foreign) member in the Russian Academy of Sciences (since 2003). He is also an active consultant for several local industries in the field of environmental protection, a national expert for the horizontal activities of FP6 and FP7 (EU), and he is acting often as a reviewer/evaluator for scientific publications, as well as for several EU or national research projects. He is also member of the Editorial Board of scientific publications (Separation Science & Technology, Water Research, Journal of Hazardous Materials and Chemosphere – among others), as well as a member of the Organizing and Scientific Committee of several national and international conferences (over 20).