Mechanical pretreatment

Coarse sieves

Coarse screens are installed at the inlet to the wastewater treatment plant. In the influent, coarse solids are retained from the wastewater using screens with apertures or mesh sizes ranging from 5 to 10 mm. The primary purpose of these screens is to protect downstream pumps.

Oil separator

Because oil has a lower density than water, it always rises to the water's surface. An oil separator is a basin equipped with a submerged baffle or pipe. The floating oil is retained, while the denser, oil-free water can flow out beneath the baffle or pipe and be discharged further. An automatic oil removal system continuously extracts the oil floating on the surface.

Sand separator

The purpose of this device is to remove sand and other abrasive particles from wastewater. Unlike in an oil separator, the solids in the wastewater settle due to their higher density. Within the sand trap, the flow velocity of the wastewater—which is heading toward the treatment plant—is reduced to below 0.5 m/s through an abrupt increase in the basin's cross-sectional area. The solids contained in the wastewater settle at the bottom of the sand trap. They can then be removed—either manually or automatically—on a continuous basis using a scraper or an air-lift pump (mammoth pump).

Drum and curved screens

Drum screens and curved screens with mesh or aperture sizes ranging from 0.5 to 2 mm are used to remove smaller solids from the influent. In cases with high solids loading, the use of a self-cleaning drum screen is recommended. Curved screens serve as a cost-effective alternative.