Rotary Screens are used in case where waste water can be pumped to a level where the screen is located. It is difficult and expensive to locate a rotary screen below ground level. When located on ground level, Rotary Screen is indeed very economical and effective.
Rotary Screen shown above cleans it self. The Screen in this picture is in use at a slaughter house and has been working for more than 5 years.
Usually a Rotary Screen is made in Stainless Steel.