DOI QR코드

DOI QR Code

Simulation study of DAF flotation basin using CFD

전산유체해석기법을 이용한 용존공기부상공정의 유동해석

  • Received : 2013.01.29
  • Accepted : 2013.04.15
  • Published : 2013.04.15

Abstract

Algae boom (Red tide) in south coastal area of Korea has been appeared several times during a decade. If algae boom appears in the desalination plant, media filter and UF filter are clogged quickly, and the plant should be shutdown. In general, Algae can be removed from water by flotation better than by sedimentation, because of the low density of algal cell. The purpose of this study conducts the CFD simulation of DAF flotation basin to apply the design of the dissolved air flotation with ball filter in the Test Bed for SWRO desalination plant. In this study, Eulerian-Eulerian multiphase model was applied to simulate the behavior of air bubbles and seawater. Density difference model and gravity were used. But de-sludge process and mass transfer between air bubbles and seawater were ignored. Main parameter is hydraulic loading rate which is varied from 20 m/hr to 27.5 m/hr. Geometry of flotation basin were changed to improve the DAF performance. According to the result of this study, the increase of hydraulic loading rate causes that the flow in the separation basin is widely affected and the concentration of air is increased. The flow pattern in the contact zone of flotation basin is greatly affected by the location of nozzle header. When the nozzle header was installed not the bottom of the contact zone but the above, the opportunity of contact between influent and recycle flow was increased.

Keywords

References

  1. American Water Works Association (AWWA). (1999). Water quality & treatment 5th edition. McGraw Hill, pp.7.47-7.61
  2. Crossley, I.A., Rokjer, D. M. & Kim, J. (1999). "Optimizingthe DAF process utilizing two phase 3D CFD modeling." AWWA Proceedings, Chicago.
  3. Edzwald, J.K. and Haarhoff, J. (2012). Seawater coagulation and dissolved air flotation pretreatment for reverse osmosis water plants, presentation at the 6th International IWA Conference on Flotation for Water and Wastewater Systems, Columbia University, NY
  4. Fawcett, N.S.J. (1997). "The hydraulic of flotation tanks; computational modeling." Proceedings of International Conference on Dissolved Air Flotation, London, April 1997, CIWEM, London, pp. 51-52.
  5. Hague, J., Ta, C.T., Biggs, M.J. and Sattary, J.A. (2001). "Small scale model for CFD validation in DAF application." Water Science and Technology, Vol. 43, No. 8, pp. 167-173.
  6. Han, M.Y. (2001) Modelling of DAF: the effect of particle and bubble characteristics, Journal of water supply: Research and technology- AQUA, 51(1), pp. 27-34
  7. James K. Edzwald. (1995). "Principles and applications of dissolved air flotation." Water Science and Technology, Vol. 31, No. 3-4, pp. 1-23.
  8. S.B. K won, N.S. Park, S.J. Lee, H.W. Ahn and C.K. Wang. (2006). "Examining the effect of length/width ratio on the hydrodynamic behaviour in a DAF system using CFD and ADV techniques." Water Science and Technology, Vol. 53, No. 7, pp. 141-149.
  9. Ta, C. T., Beckley, W.J. and Eades, A. (2001). "A multiphase CFD model of DAF process." Water Science and Technology, VOl. 43, No. 8, pp. 153-157.
  10. Voutchkov, N. (2010). Seawater Pretreatment, Water Treatment Academy, Bangkok, Thailand.
  11. Kim, S .H., Yoo, J.S., Park, H.K. (2004). "Collision efficiency estimation in the DAF contact zone using computational fluid dynamics" Journal of KSWW, 18(2), pp. 201-207.