Vikas Engineering

A clarifier is a sedimentation tank used in water treatment, sewage treatment plants (STP), and effluent treatment plants (ETP) to remove suspended solids from wastewater by gravity settling. It is one of the most important units in treatment plants because it separates solid sludge from clarified water.

In a clarifier, wastewater flows slowly through a large circular or rectangular tank, allowing heavier particles to settle at the bottom while clear water overflows from the top.

Basic Working Principle

Clarifiers operate on the principle of gravity sedimentation.

1. Wastewater enters the clarifier through the inlet pipe.

2. Flow velocity is reduced so suspended solids can settle at the bottom.

3. Settled solids form sludge at the bottom of the tank.

4. A mechanical scraper mechanism moves the sludge toward the sludge hopper.

5. Clarified water overflows through the outlet weir and moves to the next treatment stage.

Main Components of a Clarifier Types of Clarifiers 1. Primary Clarifier

Used before biological treatment to remove large suspended solids.

Applications:

• Sewage Treatment Plants

• Industrial wastewater treatment

Removal efficiency:

• 50–60% suspended solids

2. Secondary Clarifier

Used after biological treatment to remove biological sludge.

Applications:

• Activated sludge process

• MBBR / FBBR systems

Removal efficiency:

• 80–95% suspended solids

3. Lamella Clarifier

Uses inclined plates to increase settling surface area.

Advantages:

• Compact design

• High efficiency

Used in:

• Industrial ETP

• Drinking water treatment

Typical Clarifier Size (Example) Applications

Clarifiers are used in many industries:

• Sewage Treatment Plants (STP)

• Effluent Treatment Plants (ETP)

• Textile industries

• Chemical industries

• Pharmaceutical plants

• Food processing plants

• Drinking water treatment plants

Advantages

• Efficient removal of suspended solids

• Simple operation

• Low energy consumption

• Continuous sludge removal