These polymers increase floc size by charged site binding and by molecular bridging. Flocculation, the agglomeration of destabilized particles into large particles, can be enhanced by the addition of high-molecular-weight, water-soluble organic polymers. Coagulation can also be effected by the addition of water-soluble organic polymers with numerous ionized sites for particle charge neutralization. These inorganic salts neutralize the charge on the particles causing raw water turbidity, and also hydrolyze to form insoluble precipitates, which entrap particles. Coagulation can be accomplished through the addition of inorganic salts of aluminum or iron. The following steps in clarification are necessary for particle agglomeration:Ĭoagulation. Sedimentation or subsidence alone, without prior coagulation, results in the removal of only relatively coarse suspended solids.įinely divided particles suspended in surface water repel each other because most of the surfaces are negatively charged. Sedimentation refers to the physical removal from suspension, or settling, that occurs once the particles have been coagulated and flocculated. Coagulation is necessary for the removal of the colloidal-sized suspended matter.įlocculation is the process of bringing together the destabilized, or "coagulated," particles to form a larger agglomeration, or "floc." Once neutralized, particles no longer repel each other and can be brought together. The combination of these three processes is referred to as conventional clarification.Ĭoagulation is the process of destabilization by charge neutralization. Removal is generally accomplished by coagulation, flocculation, and sedimentation. The suspended matter can consist of large solids, settable by gravity alone without any external aids, and nonsettleable material, often colloidal in nature. Suspended matter in raw water supplies is removed by various methods to provide a water suitable for domestic purposes and most industrial requirements.
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