Standard Article

Gravity Separation/Sedimentation

Municipal Water Supply

  1. Rasheed Ahmad

Published Online: 15 JUL 2005

DOI: 10.1002/047147844X.mw181

Water Encyclopedia

Water Encyclopedia

How to Cite

Ahmad, R. 2005. Gravity Separation/Sedimentation. Water Encyclopedia. 1:259–261.

Author Information

  1. Khafra Engineering Consultants, Atlanta, Georgia

Publication History

  1. Published Online: 15 JUL 2005


Gravity separation or sedimentation is the step in conventional water treatment systems that follows flocculation and precedes filtration. Its purpose is to enhance the filtration process by removing particulate matter. Sedimentation requires that the water flow through a basin at a slow enough velocity to permit the particulate matter to settle to the bottom of the basin before the water exits the basin. The equipment required for this process includes a settling basin of rectangular, square, or circular configuration. The basin includes provisions for inlet and outlet structures and a sludge collection system. In addition, sedimentation systems are optionally equipped with tube or plate settlers to improve performance.


  • sedimentation;
  • surface overflow rate;
  • weir rate;
  • plate settlers;
  • tube settlers;
  • particulate matter;
  • discrete settling;
  • flocculant settling;
  • hindered settling;
  • compression settling;
  • clarification;
  • clarifier;
  • Stokes' law