Clarifier

November 20, 2018

Clarifiers are settling tanks in which suspended solids and other matter settle to the bottom. These tanks are often circular in shape. Water clarifiers are at times called settlers. They are used to separate solid sediments from a liquid for clarification or thickening. The solid and liquid mixture in the tank is given some time to settle. 

This is done with the help of a rake system to direct the solids to the bottom of the tank. Gravity pulls the sediments to the bottom of the tank leaving liquid at the top to be recovered. Water clarifiers are commonly used in various industries to help in the separation of products and recovery. Some of these industries include power generation, petrochemical, paper industry, oil and gas, sewage treatment and the mining industry. 

Major types of clarifiers

There four major types of water clarifiers:

Circular clarifiers

These are the most common types of water settlers. They are used where the diameter of a basin is 50 to 200 feet (15 to 61m). It is supported by a centrally located column, and the inlet pipe is found beneath the floor of the tank and then goes up via the column getting to the feed well. The circular clarifier has four sections each with own duty. The feed well, also called the inlet, offers a smooth transition from high rough velocity to a low and uniform velocity that is needed at the settling section. 

The settling zone that receives low uniform velocity needs to be large to meet the overflow rate and depth that is required. The third section is the outlet zone that offers a smooth transition from the velocity from the settling area to the much higher outlet velocity. The higher outlet velocity is limited to values that do not exceed 14 gpm per linear foot of outlet plate. The sludge zone is the fourth section. It collects and puts together the solids removed in the settling zone. It eradicates this sludge from the settler without interrupting the sedimentation zone. 

Rectangular Clarifiers

This settler somehow has a basin that has a part of it taken through a center feed clarifier. They also have inlet and outlet points at opposite ends. Rectangular clarifiers have a length to width ratio of 4:1. Sludge is removed using a dual-purpose flight system with two parallel conveyor chains operating the length of the basin and the rake flights passing across the width between the chains. 

Parallel plate clarifiers

Smaller plant flow rates need parallel plate clarifiers. Sediments settle on the plates and the clarified water exits from the top via orifice holes. Solids slide down the plate surfaces to the sludge hopper, and through flocculation, the solids go down the inclined surfaces. 

Drag clarifiers

Drag clarifier is a modification of the rectangular clarifier. It removes dense gritty and anhydrous solids. Water is drained from solids which are dragged from the vessel moving up the beach. Chemical flocculation in the tank improves effluent clarity. 

Oil/water clarifiers

Oil/water clarifier is used to separate oil from wastewaters in major industries. Chemical treatment is used to separate oil and water. 

There are other minor types of clarifiers used in various industries for the purposes of water treatment. 

Rain for Rent is a leading supplier of water clarifiers. To learn more about oil and water clarifiers, read these water filtration solutions from Rain for Rent

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