Municipal and industrial wastewater contains large solids and grit that can interfere with treatment processes, or cause undue mechanical wear and increased maintenance on wastewater treatment equipment. To minimize potential problems, these materials require separate handling. Preliminary treatment removes these constituents from the influent wastewater.
Screening is the first unit operation used at wastewater treatment plants. Wastewater screening removes objects such as rags, paper, plastics, metals and gross solids to prevent damage and clogging of downstream treatment equipment.
Rotary Screen with Integrated compactor
Operation: screenings slide down into the skimmer and fall through into the rotating screw. The screenings move through the screw and are pressed towards the slotted screen. A thrust plate at the end of the screen exerts counter pressure needed to compress the screenings and dewater them as much as possible. When the thrust plate resistance is broken, the dewatered screenings fall into a container. Treated water, free of solid pollutants, flows out from the lower part of the rotary screen. The screened water returns directly to the outlet tank of the screen.
Principle of working: Main operational part of rotary screen is a slotted tube which is a welded structure with support profiles which are rods in the axial direction of the tube and surface profiles spirally wound around the support profiles. Water is conveyed by a pump or flows by gravity on the slot tube and passes through the slots (slot sizes 0.25-2.50mm). The solid pollution that exceeds the dimension of the slot, remains on the exterior of the rotating slot tube and it is scrapped and falls down into a container. Treated water, free of solid pollution, flows out from the lower part of the rotary screen. The inlet tank is equipped with an overflown to drain away the excessive wastewater back to the pumping station.
Parabolic screens are used to efficiently separate mechanical impurities from the industrial waste water influent streams. The best results are to be found in the food processing industry e.g. slaughterhouses, meat-processing, dairies and canning factories, principally as the fine filtration stage before the chemical treatment on the D.A.F. (dissolved air flotation).
Description: The main part of the facility is a curved/parabolic screen created by winding a wire with a trapezoidal profile, with a space between the threads. The slot size is generally 0.5mm - 1,5mm.
Polluted waste water is transported by a pump or flows by its own gravity into the inlet tank. The water stream goes calm in the inlet tank and when water levels reaches overflow edge, the distributing plate dispatches the water on the parabolic screen. Water flows through the screen and falls into the outlet tank, then through the pipe out of the screen unit.
Reconditioned Parabolic Screens