ESEL Paper Review_201201018

By Hong Guo

Mail: hongguo@gist.ac.kr

Phone: (+82) (0)10 82276568

1, Title and Author

Title: A CFD-based simulation study of a large scale flocculation tank for potable water treatment

Journal: Chemical Engineering Journal

Authors:

K.Samars, A.Zouboulis, T.Karapantsios, M. Kostoglou*

Division of Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, University Box 116, 541 24 Thessaloniki, Greece

2. Summary of Paper

This paper introduced a methodology for simulating the operation for flocculation tanks for potable water treatment in the presence of very low solids concentration. The author found that flocculation is need be enhanced by increasing the solids concentration in the flocculation tank by recycling sludge from the sedimentation tank. In addition, the paper provided the guideline, which gives the idea how the present computational tool can be applied for the optimization of the design and operation of flocculation tanks treating potable water.

2.1 Results

For avoiding the computational cost of handling simultaneously hydrodynamic and physicochemical aspect is to decompose and here the author select the advanced hydrodynamics with simple physicochemistry.

The distribution of turbulent energy dissipation rate shows that the distribution is highly non-uniform showing a maximum value close to the impeller tip and decreasing towards the walls of the tanks except at the regions of the inlet flows where a local increase is observed.

Investigation for the presence of fresh particle and flocculent in the tank:

Surprisingly, the author found that the floc size does not grow in the region close to the impeller. The flocs actually grow in regions of high residence time but there regions hardly contribute to the floc size in the peripheral outflow to the sedimentation tank

Influence of mud recirculation on the floc culation process:

The sedimentation efficiency is not determined here by the growth of the incoming particles but from the amount of these particles that have coagulated

with large mud particles that have been recirculated from those settled in the sedimentation tank.

3. Contribution:

A special simulation approach is developed. However, we could find that it sacrifices the details of particle size distribution in order to gain computational efficiency. Also the AFX was successfully applied to modeling the flocculation tank. Being as the second part of water treatment plant, the flocculation tank is important for system design and evaluation. Also, for future sedimentation study, this paper gives the design guideline for future study.

4. Author information:

Email: Ksamaras@chem.auth.gr