What is water treatment clarifier?

Clarifier is a sink that uses the principle of gravitational settling to continuously remove precipitated deposited solids while filtering water. It is usually used to remove solid particles from liquids for clarification and thickening. The thickened impurities discharged from the bottom of the tank are called sludge and the particles floating on the surface of the liquid are called scum. Clarifiers are required where there is a high concentration of suspended solids in the raw/wastewater. Almost all wastewater treatment plants (clarifiers) will have settling tanks.

Sedimentation tanks play a vital role in the treatment of wastewater, and primary treatment involves the removal of floating and settleable solids by sedimentation.

Clarification is an important step in the wastewater treatment process, where solids are removed by gravity settling to provide a clarified and clean liquid. These are also used to remove substances such as oil, grease, and solids. Clarifiers are usually divided into two types.

  1. Primary clarifiers: These clarifiers are used to separate settleable solids from the incoming raw wastewater. They are located downstream of the plant screening process. This entire process is called primary clarification and is also referred to as sedimentation.
  2. Secondary clarifiers: These clarifiers are located downstream of the biological treatment. Their main purpose is to separate the treated wastewater from natural substances. Its main objective is to return the activated sludge. The whole process is called secondary clarification.

Types of clarifiers in water treatment

Circular clarifiers

Circular clarifiers can be used in water or wastewater treatment systems. Typically the water treatment tank is circular and it includes a larger influent well to provide the required flocculation time. Mixing is also added to achieve economical flocculation.

Circular clarifier
Circular clarifier

Designed to exacting specifications, clarifiers are shop-built for bolt-on assembly and include a reinforced inlet well and feature a cast iron drive housing, deep scraper blades, adjustable scrapers and full-surface adjustable skimmers. Round sludge collectors are available in full or half bridge designs.

Rectangular clarifiers

Rectangular clarifiers are commonly used in very large or space-constrained municipal and industrial spaces for separation processes that remove settled and suspended solids from liquids.

Rectangular clarifier
Rectangular clarifier

Suitable for primary, secondary, rainwater harvesting and water plant services, they are a high quality option for new and existing rectangular clarifier installations. In operation, scrapers mounted on two parallel metal or non-metal chains scrape settled solids along the bottom of the tank to the sludge hopper. On the return trip, the craft can skim the water surface and concentrate the floating material in the scum removal unit.

To aid gravity settling, an inclined plate clarifier can be used to quickly settle the floc. The plates are placed at an angle (55-70º) and the water flows upward. Due to the inherent weight, the solids cannot move at the same speed and tend to settle on the provided plates. The slope of the plate ensures that the solids slide down into the collection chamber.