1 Media Filtration
The common method of removing suspended solids from water is multi media filtration. Multi-media filter to layered anthracite, quartz sand, finely garnet or other materials for the bed. The top layer of the bed consists of lightweight and coarse-grained material, while the heaviest and finest materials are placed at the bottom of the bed. The principle is to filter by depth-the larger grains in the water are removed at the top and the smaller particles are removed from the depths of the filter medium.
Because the colloid suspension is very small and because of the repulsion between the dielectric charges, the individual filtration does not work. In these cases, flocculants or flocculating chemicals must be added before filtration. Commonly used flocculants are ferric chloride, alum and PAC.
2 Micro Flocculation
If the colloid in the original water before the filtration flocculation or coagulation treatment, can greatly improve the efficiency of the medium filter, so that the output of SDI to reduce to about 5. Ferric sulfate and ferric chloride can be used to stabilize the negative charge on the colloid surface, the colloid is captured in the new eco-ferric hydroxide micro-floc, the use of aluminum flocculant is similar to the principle, but because it may have residual aluminum ion pollution problems, not recommended, unless the use of polymeric aluminum. Rapid dispersion and mixing of flocculant is important, it is recommended to use static mixer or the injection point in the booster pump suction section, usually the best dosage is 10-30mg/l, but the specific project should be determined to add dosage.