After undergoing coagulation treatment, the waters will be transferred to another basin where will actually start accretion. Indeed, nothing prevents the gathering of more then neutralized colloids. We must therefore maintain a slow stirring to encourage accretions. It is accelerated by the addition of polymer, that is to say a large molecule formed by the repetition of basic pattern that traps colloidal materials and agglomerated forming large flakes which settle by gravity. This is the "flock".
The waters seeps through the network inside the cylinder and is sent to subsequent treatments, while the material is retained on its surface.
After gathering the different small particles of much larger, we must now settle this. In a still body of waters, the heavier suspended particles than waters are subject to their apparent weight (actual weight less buoyancy). They are falling slowly to build up on the bottom: the settling. Their fall velocity obeys Stokes' law:
The purification is carried out by passing the raw waters (from rivers or lakes) through various types of implants removal of organic and inorganic material. The removal methods used can physical, chemical-physical and biological function of type of substances to be eliminated from raw waters entering the plant. The substances to be removed during the purifying treatment can of natural and man; the first type comprises.
The primary sedimentation uses the force of gravity for removing the solid sediments predominantly inorganic (sand, loam, silt, etc.). It is adopted as pretreatment physical limited to waters with high turbidity (1,000 mg / l) and / or with silica in suspension. In these cases, is inserted upstream of flocculation in order to lighten the load coming.
The first filtration principles were inspired by the natural filtering the waters passing through the different layers of Earth, before reaching the "underground tanks." Unfortunately, this process is far too slow to handle large amounts of waters. Note however that the thus filtered waters is often of excellent quality.
Now filters are used batteries according to treatment suffered by the waters before you get to this stage. For a conventional waters treatment plant, various treatments are: rapid mixing with a coagulant, flocculation, sedimentation. Filtration materials encountered in treatment of drinking waters are numerous.
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