Settling basin
A sedimentation basin (also known as a sedimentation system ) is an almost flow-free basin in which water constituents are sedimented by gravity and thus a separation of substances that can settle from a liquid can be achieved.
Differentiated into primary and secondary clarifiers , settling basins are used in sewage treatment plants to purify wastewater , but they can also serve as part of the drainage systems of streets and buildings.
Settling basins in sewage treatment plants
Decantable substances, i.e. sufficiently large particles that are heavier than water, can be removed from liquids (usually water or waste water) with the help of sand traps or sludge collectors , depending on the particle size . As the water flows through a shaft, heavier particles such as sand, earth, grinding dust, etc. sink into the lower part of the container and remain there.
If the pool walls are steep, the deposited substances can slide into a funnel tip by gravity and be removed there. However, this requires a considerable pool depth. Mostly shallow basins are used in which a mechanical scraper such as a chain scraper conveys the sludge to the funnel and thus to the removal.
Special cases provide settling tank is integrated with septic tanks. The so-called Imhoff tank of waste water technology has below the settling chamber, a digestion chamber in which the sludge slides automatically. Since this digester is not heated, the stabilization of the sludge is not excellent. Digester gas cannot be used.
In small sewage treatment plants, multi-chamber settling basins are connected upstream for mechanical cleaning. These are not only dimensioned for the space required for sedimentation, but also for the stacking of the sludge up to disposal (utilization of the vehicle volume).
Settling basins in infiltration systems
Such settling basins are also stored as sludge collectors in front of infiltration systems. The sedimentation of the sludge reduces the penetration of fine particles into the subsoil (sand, gravel, earth). This prevents the soil from being compacted, which would then no longer be able to absorb the seepage water so easily.
The effectiveness of such a sludge collector depends on the diameter of the shaft and the depth of the sedimentation chamber. The fine particles have a slow sink rate. Therefore, a shaft diameter of 0.8 m with a sedimentation room depth of 1 m is a minimum for rainwater infiltration systems . A downwardly bent pipe forms the drain for the water into a collecting basin or to the drainage gallery with sand, gravel or drainage pipes for further distribution.
Settlement basins in mining
In mining , concrete pools or ponds artificially created by embedding dams, which are used to clarify wastewater (sludge) from the processing of mineral raw materials, are called settling basins , sewage or sludge ponds , industrial settling plants ; sink and mud ponds are widespread in the Saarland .