Sedimentation

In chemistry, the retention of particles in suspension is referred as sedimentation. It is due to the movement of fluid particles in response to the various forced over them. Sedimentation is also referred as clarification. Various forces are listed below.

• Gravitational force
• Centrifugal force
• Electromagnetic force

The suspended particles can be clay or silt deposition originated in water. The floc or sedimented material can be treated with the help of coagulating agent like lime softening. When the velocity of water is decreased below the particles velocity limit, then particles can never remain suspended in solution anymore. If the velocity does not support the process of sedimentation then the particles are transported by gravitational force.

In geology, sedimentation is means of erosion opposite. Deposition of sediment results in the formation of sedimentary rocks. Sedimentation terminates the transport of fluid particles by means of true bed load transport or by saltation. Sedimentation refers to end of settling process however settling is the process of suspended solids falling through the liquid particles. Sedimentation includes separation of particles ranging in various sizes from dust pollen, single molecules such as proteins and peptides to large rocks which are suspended in water. Small molecules like aspirin can be sedimented in a significant way. In biology, sedimentation helps in separation of cells from cultured media.

Factors that affect Sedimentation:

• Particle size: Type and size of particles has a significant role in sedimentation processing tank. Due to present of sand, silt and density of particle, it can be sedimented so easily.
• Shape: Particle shape may affect settling characteristics. For instance round particles are sedimented easily when compared to irregular edged particle.
• Charge: Particles of same charge repel each other and of opposite charge attract each other.
• Temperature: If the temperature decreases settling of particles take longer time. Hence detention time increases.
• Currents: Density current and eddy currents are produced in sedimentation tank.

Questions:

• What are sedimentation zones?
• What are factors affecting sedimentation process?
• What is sedimentation?