Coagulation and flocculation are water treatment processes that are used to remove suspended particles and other impurities from water.
Coagulation is the process of adding a specific cationic chemical to water which causes suspended particles and other impurities to clump together into larger particles called pin-flocs. The coagulant neutralizes the electrical charges on the surface of the particles which causes them to be suspended in solution rather than precipitate. When the charges of repulsion have been neutralized by the coagulant, the minute or even smaller particles can agglomerate enough to be precipitated by gravity, if their masses are large enough. If not, a flocculant is then usually additionally applied to cause agglomeration of the pin floc into much larger masses which will then precipitate out of solution.
Flocculation is the process of gathering together various suspended solid particles in an aqueous system with a long chain, highly charged, organic polymer which is electrically attracted to the net surface charge of the particles. The net charge can be referred to as the Zeta Potential, a measurable quantity. The flocculant solution is mixed the solids laden water to encourage the flocculant/solids particles to be bound together. Then they can form larger, heavier and denser particles that will easily settle out of the solution. This is usually performed using mechanical mixing in mixing chambers of clarifiers on in feed line to settling tanks or ponds. The solids bound with the flocculant are called floc. Once the flocs have settled out of the clarified water or supernatant, it can be decanted or filtered to remove the remaining impurities. The supernatant may be sent for reuse, recycling or legal disposal.
Coagulation and flocculation are often used in conjunction with other water treatment processes, such as sedimentation and filtration, to achieve the desired level of water quality. The specific coagulant and flocculant used will depend on the type and concentration of impurities in the water, as well as other factors such as pH, temperature, governing regulations and end use requirements.
Coagulation and flocculation are important steps in the water treatment process that help to remove impurities and improve the quality of water. Further information is available from the above manufacturer.