Clarifier

A clarifier is a device or process that removes suspended solids from liquids to produce clarified liquid. Clarification is widely used in water and wastewater treatment as well as in various industrial processes where solids must be separated from liquids.

In operation, wastewater or process streams enter a clarifier where solids settle to the bottom by gravity or are removed by flotation. The clarified liquid exits over an overflow weir, while a sludge layer forms at the bottom. Mechanical clarifiers incorporate scrapers or rakes to collect settled solids for removal. Some designs use inclined plates (lamellar clarifiers) to increase the effective settling area. Dissolved air flotation (DAF) clarifiers use air bubbles to lift solids to the surface for skimming.

Chemically assisted clarification adds coagulants and flocculants to promote aggregation of fine particles and improve settling.

In the dairy industry, clarifiers refer to equipment that separates fat and solids from milk, often by centrifugation. In municipal and industrial settings, clarifiers are key components of drinking water treatment and wastewater treatment trains, typically placed after coagulation/flocculation or primary sedimentation to produce clarified effluent.

Key design considerations include retention time, hydraulic loading, flow distribution, sludge removal, and maintenance of scraper mechanisms.