Journal of Korean Society of Water and Wastewater (상하수도학회지)

The Korean Society of Water and Wastewater (대한상하수도학회)
권호 표지

An assessment on feasibility of flotation as a secondary clarifier of an activated sludge process

생물반응공정에 대한 고액분리조로서 부상공정의 적용성 평가

  • 정종민 (서울대학교 건설환경공학부) ;
  • 김윤중 (서울대학교 건설환경공학부) ;
  • 조강우 (한국과학기술연구원) ;
  • 이상협 (한국과학기술연구원) ;
  • 홍석원 (한국과학기술연구원) ;
  • 정태학 (서울대학교 건설환경공학부)
  • Received : 2008.08.18
  • Accepted : 2008.10.09
  • Published : 2008.10.15
Download PDF
⟨ Previous Next ⟩

Abstract

An experimental study was carried out to evaluate the potential of flotation process for the secondary clarifier of an activated sludge process. Flotation techniques, applied in this study, include electrofloation (EF) which generated fine bubbles smaller than $35{\mu}m$ in average and diffuser flotation (DF) which generated fine bubbles smaller than $55{\mu}m$ in average. The batch experiments were done with activated sludge displaying various characteristics. It was shown that the efficiency of solids/liquid separation was reduced as the diluted sludge volume index ($DSVI_{30}$) of activated sludge increased. The dependency, however, gradually decreased as the gas to solids (G/S) ratio increased. Thickening efficiency of EF was more than 2~10 times and DF process was more than 1.5~5 times as compared with gravity sedimentation (GS). Stable sludge blanket was maintained regardless of sludge settleability when the G/S ratio was 0.019 in the EF. On the other hand, Serious deterioration in the sludge blanket was observed in the DF depends on G/S ratio and sludge settleability. And For EF and DF, the suspended solids concentration of effluent was not nearly influenced on settleability of activated sludge and more clear than GS. A biological nutrient removal (BNR) process, combined with EF as a secondary clarifier was operated for three months. The mean MLSS (mixed liquid suspended solids) concentration in the reactor and mean solids concentration of return sludge were estimated to be 5,340 mg/L and 16,770 mg/L, respectively. The water quality of effluent was considerably stable and low value was accomplished, that was, standard suspended solids concentration $0.07{\pm}0.51mg/L$ and standard turbidity $1.44{\pm}0.56NTU$. The EF could be applicable for enhancement of efficiency of activated sludge system as well as improvement of the water quality of effluent.

Keywords

Acknowledgement

Supported by : 서울대학교

References

  1. 정종민 외 (2007) 활성슬러지의 고액분리를 위한 부상공정의 특성에 관한 연구, 대한상하수도학회.한국물환경학회 2007 공동 춘계학술발표회 논문집, F 248-257.
  2. APHA, AWWA, WEF (1998) Standard methods for the examination of water and wastewater, 20th ed. American Public Health Association, Washington, DC, USA.
  3. Bratby, J. R. and Ambrose, W. A. (1995) Design and control of flotation thickeners. Wat. Sci. Tech., 31(3-4), 247-261.
  4. Cho, K.W., Kim, Y.J., Choi, Y.G., Hong, S.W., Choi, Y.S. and Chung, T.H. (2007) Significance of gas to solids ratio in clarification and thickening of activated sludge by electroflotation, Proceeding of 5th international conference on flotation, September 11-14, Seoul, pp.239-246.
  5. Choi, J.G., Bae, T.H., Kim, J.H., Tak, T.M. and Randall, A.A. (2002) The behavior of membrane fouling initiation on the cross-flow membrane bioreactor system, J. Membr. Sci., 203, pp.103-113. https://doi.org/10.1016/S0376-7388(01)00790-6
  6. Da Rosa, J., Dias de Souza, M.L., Rodrigues, R.T. and Rubio, J (1999) Wastewater treatment by nonconventional flotation. In: Gaballah, L., Hager, J., Solozabal, R. (Eds.), Proceedings of Global Symposium on Recycling, Waste Treatment and Clean Technology-REWAS'99, TMS-Inasmet, San Sebastian/Spain, pp.2123-2132.
  7. Gabb, D. M. D., Ekama, G. A., Jenkins, D., Wentzel, M. C., Casey, T. G. and Marais, G. R. (1996) Filamentous organism bulking in nutrient removal activated sludge systems. Paper4. System configurations and operating condition to develop low F/M filament bulking sludges at laboratory-scale. Water Sa, 22(2), pp.127-137.
  8. Han, M.Y., Kim, W.T. and Dockko, S. (2001) Collision efficiency factor of bubble and particle (${\alpha}$bp) in DAF : theory and experimental verification. Wat. Sci. Tech., 43(8), 139-144.
  9. Han, M.Y. and Dockko, S. (1999) Zeta potential measurement of bubbles in DAF process and its effect on the removal efficiency, Water Supply: the review journal of the international water supply association, 17(34), pp.177-182.
  10. Hultman, B., Loen, M., Karlsson, U., Li, P.H. and Monlina, L. (1991) Prediction of activated sludge sedimentation based on sludge indices, Wat. Sci. Tech., 24, pp.33-42.
  11. Kalinske, A.A. and Evans, R.R. (1953) Comparison of flotation and sedimentation in treatment of industrial wastes, Proceeding of Industrial Waste Conference 8th, pp.64-71.
  12. Ketkar, D. R., Mallikarjunan, R. and Venkatachalam, S. (1991) Electroflotation of quartz fines. Int. J. Miner. Process., 31, 127-138. https://doi.org/10.1016/0301-7516(91)90009-8
  13. Metcalf and Eddy, Inc. (2003) Wastewater Engineering: Treatment, Reuse and Disposal, Fourth ed., McGraw- Hill Company, New York.
  14. Park, C.H., Hong, S.W., Lee, S.H. and Choi, Y.S. (2008) A pilot study on air flotation processes for retrofitting of conventional wastewater treatment facilities, Journal of Korean Society of Water and Wastewater, 22(3), pp.329-336.
  15. Rubio, J., Souza, M.L. and Smith, R.W. (2001) Overview of flotation as a wastewater treatment technique, Minerals Engineering, 15, pp.139-155. https://doi.org/10.1016/S0892-6875(01)00216-3
  16. Rubio, J. and Tessele, F. (1997) Removal of heavy metal ions by adsorptive particulate flotation. Minerals Engineering, 10(7), pp.671-679. https://doi.org/10.1016/S0892-6875(97)00047-2
  17. Santander, M., Da Rosa, J.J. and Rubio, J. (1999) Advances in flotation in waste streams treatment. In: Proceedings of International Mining and Environment Congress: Clean Technology, Third Millenium Challenge-Lima-Peru, pp.591-602.
  18. Urbain, V., Block, J. C. and Manem, J. (1993) Bioflocuulation in activated sludge: an analytic approach, Water Research, 27, pp.829-838 https://doi.org/10.1016/0043-1354(93)90147-A