The general basic principle of wastewater treatment systems is to bring pollutant loads together, precipitate or float them using density differences, and then physically separate them from water. These steps are applied to many areas of the treatment system and are scrapers is used. DAF System is indispensable for sludge settling and concentration tanks and sand and oil separation processes.

Although there are many types, they are roughly divided into two groups: rotary scrapers and linear scrapers:

Circular Scrapers: It is used in sludge settling and thickening tanks where the scraper tank is circular. Its capacity is determined depending on the pool diameter, design and mud load. These skimmer types can be equal in length to the radius of a tank or its entirety. It helps to remove the mud settled at the bottom from the environment by scraping it.

Linear Scrapers: This type of scrapers are used in rectangular type tanks. It proceeds by skimming from one side of the rectangular pool to the other. It advances from the bottom in sand traps and from the surface in oil traps and DAF systems. The settled sand is scraped from the bottom, and floating foam and oils are removed from the surface. When the process is finished, the scraper returns to the beginning again.