Types of sedimentation tank

Topic : Types Of Sedimentation Tank

By : Sagar K. Vekariya

The process of sedimentation is designed to remove large particles of contamination from water and wastewater.

Sedimentation tanks can be installed before or after water and wastewater completes the treatment process.

Sedimentation tanks are also known as settling tanks or wastewater clarifiers.

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1) Rectangular Tanks

2) Circular Tanks

3) Hopper Bottom Tanks

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These are rectangular in plan and consists of large number of baffle walls.

The function of baffle wall is to reduce the velocity of incoming water.

Openings are given in baffle walls at different height.

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Continuous flow in tank.

Supervision & labor work is less.

Less head loss due to outlet given at the top of

tank.

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Tanks are arranged in series so it is easy to maintenance of one(any one).

Because of continuous flow in tank time waste rate is low.

To store pure water there is no necessity of tank, so construction cost is less.

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Circular sedimentation tank is costly at the

view of construction.

For dispose the sludge mechanical scraper

available at bottom of the tank.

Over flow rate of this type of tank is 1500

lit/hour/m2.

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I. Radial flow

II. Spiral flow

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The water enters in this tank through the central pipe placed in-side the deflector box.

Mostly to reduce the velocity of flow there is provide circular baffle box.

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All the impurities settled at the base of tank. The sludge is removed by scraper(known as raking arm).which continuously move around the floor at very small velocity.

The maximum velocity of raking arm does not exceed 4.5 m/h.

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Water enters through

the vertical silt.

There is raking arm

with blades in the

tank, which is allows

the water move along

the circumference of

the tank.

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While water moving at very low velocity allows its suspended impurities to settle in the tank, which can be remove from sludge outlet.

The clear water drawn from outlet pipe.The length of outlet is not exceed 1/8

circumference of the tank.


The shape of the base of this tank is hopper type. This are vertical flow tanks, because water flows

upward & downward in these tank. The water enters in this tank from top inlet channel. Because of deflector box water flows from upper to

lower.

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Impurities settled at the bottom of the tank.

Pure water taken by draw off channel.

Sludge outlet pipe is used to take out the sludge from tank.

Over flow rate = 2000 lit/hour/m2

Detention period = 3 – 4 hours


Types of sedimentation tank

Engineering

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