Journal of Korean Society on Water Environment (한국물환경학회지)

Korean Society on Water Environment (한국물환경학회)
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Numerical Analysis of the Outlet Structure Effect on the Flow and Settling Performance of the Rectangular Clarifiers

장방형 2차 침전지 유출부의 구조가 유동 및 성능에 미치는 영향에 대한 수치 해석적 연구

  • Kim, Youngchul (Department of Environmental Engineering, Hanseo University) ;
  • Park, Moo Jong (Department of Civil Engineering, Hanseo University) ;
  • Sheen, Dong-Jin (Department of Aero Mechanics and Mechanical Engineering, Hanseo University)
  • 김영철 (한서대학교 환경공학과) ;
  • 박무종 (한서대학교 토목공학과) ;
  • 신동진 (한서대학교 항공기계공학과)
  • Received : 2006.02.14
  • Accepted : 2006.03.23
  • Published : 2006.05.30
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Abstract

Proper operation of clarifier partly depends on outlet conditions. Effluent has to be uniformly withdrawn to prevent scouring of settled sludge and carry over of settling sludge from the clarifier. In this paper, 3-D numerical model was employed to analyze the flow and settling performance of the rectangular clarifier. There were two simulation conditions of which in the same clarifier, the first one was assumed to have a 11.5 meter weir length and the second has 8.5 meters. Shape, location and placement of the weir structure were different, but both of those outlets meet weir loading design criteria. Simulation results indicate that clarifier with longer weir generally gave strong and unstable currents at the mid-stream where the weir starts while in the clarifier with short and relatively simple weir, uniform and stable flow was observed in most parts of the settling zone, and especially at the weir region. These flow conditions affected settling performance. Effulent SS concentration from clarifier equipped with the long and complicated placement of weir was 24.5 mg/L, but 7.0 mg/L from the clarfieir having short weir length. From this study, it can be concluded that as reported from other studies, weir loading does not guarantee settling performance and 3-D numerical model can be a useful tool for determining and validating outlet structure.

Keywords

References

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