Plain sedimentation

Plain sedimentation is the process of separating impurities from a liquid by allowing the settling particles to gravitate to the bottom of the container. This operation does not involve the use of any coagulant or disinfectant. It is a simple and widely used method for the removal of suspended solids from water or wastewater.

Process of plain sedimentation

The process of plain sedimentation involves the following steps:

1. Coarse screening: Before sedimentation, the water or wastewater is usually passed through a coarse screen to remove large debris and solid objects.

2. Settling tank: The water or wastewater is then transferred to a settling tank, also known as a sedimentation tank or clarifier. This tank is designed to allow the suspended particles to settle to the bottom through the force of gravity.

3. Sedimentation: In the settling tank, the suspended particles in the water or wastewater settle down due to their weight. The settling process is facilitated by the reduced velocity of the water in the tank, which allows the particles to fall out of suspension. The settled particles accumulate at the bottom of the tank as sludge.

4. Sludge removal: The sludge that accumulates at the bottom of the settling tank needs to be periodically removed. This can be done by either draining the tank or using a sludge pump to remove the settled particles.

5. Clear water collection: The clear water, which is now free from most of the suspended solids, is collected from the top of the settling tank. It can then be further treated through additional processes if required.

Advantages and limitations of plain sedimentation

Advantages:
- Simple and cost-effective method for solid-liquid separation.
- Can remove a significant amount of suspended solids from water or wastewater.
- Does not require the use of chemicals or disinfectants.

Limitations:
- Less effective in removing fine particles or colloidal matter.
- Slow process as settling takes time.
- Requires a large space for the settling tank.
- Can be influenced by variations in temperature, flow rate, and particle characteristics.

Conclusion

Plain sedimentation is a common method for the separation of impurities from a liquid by allowing the settling particles to gravitate to the bottom of a settling tank. It is a simple and cost-effective process for the removal of suspended solids from water or wastewater. While it has its limitations, it remains an important step in many water and wastewater treatment processes.