It is used in rectangular section sedimentation tanks of medium and large-scale wastewater treatment systems. Mud, sand, etc. accumulated at the bottom of the sedimentation tank. The substances are linearly scraped from the pool bottom with pallet scrapers and directed to the sludge collection pit. The oil and foam formed on the surface are directed to the oil-foam collection compartments via scraper pallets. Bridge drive can be via concrete or moving wheels on rails.