Large, heavy particles settle out readily, but smaller and lighter particles settle very slowly or in some cases do not settle at all. This information can be recompiled into the following chart . They help in binding and strengthen the floc … They are typically used for treatment of wastewater containing colloids (suspended particles) and metal ions. Flocculants, or flocculating agents (also known as flocking agents), are chemicals that promote flocculation by causing colloids and other suspended particles in liquids to aggregate, forming a floc. Both these techniques are employed in the treatment of water. Physico Chemical Processes (EN 525) But the phenomena are also well-known from everyday life – especially coagulation. Coagulation is achieved by neutralizing the particles and thus, the repelling force between the particles is greatly reduced. As early as 2000 BC the Egyptians used al… Shown Above: The flash mix portion is also known as coagulation. If you continue browsing the site, you agree to the use of cookies on this website. Because of this, the sedimentation step is usually preceded by a chemical process known as coagulation. Typically aluminum or iron salts are used. From the numerous reviews of the fundamental theory and mechanisms of coagulation, You can change your ad preferences anytime. If you continue browsing the site, you agree to the use of cookies on this website. The chemicals are added together and the process occurs within seconds. Water supply system - Water supply system - Coagulation and flocculation: Suspended particles cannot be removed completely by plain settling. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Treatment Process to produce water that is free of chemicals and microorganisms, and is aesthetically pleasing. Colloid Entrapment Occurs when large dosages of coagulant are added which precipitate as hydrous metal oxides. Coagulant aids, also known as polyelectrolytes - which improves coagulation and for more robust floc formation 5. Flocculation (in polymer science): When a sol is colloidally unstable (I.e., the rate of aggregation is not negligible) then the formation of aggregates is called flocculation or coagulation. The results presented here provide insight to jar test data and help explain why better settling often is observed in practice for sweep-floc coagulation as compared to floc produced by a charge-neutralization mechanism. diagram the area defined as optimum sweep coagulation is the area for best settling floc, and is defined by the major parameters of alum dose of 20-60 mg/l and a pH of 7.0 to 8.0. Overview of the Process Image of floc … Larger floc does not settle as well and is more subject to breakup in the flocculation basin. When added to water, inorganic coagulants form aluminum or iron precipitates. However, a downside of metal hydroxide precipitate sweep-floc is that they add to the overall sludge volume that must be treated and removed. Coagulation in Water Treatment Flocculation brings the de-established colloidal particles together and they form large aggregates. In potable water treatment, clarification of water using coagulating agents has been practiced from ancient times. 1. Associate Professor Other particles in the water are swept up into the coagulant flocs and are removed during sedimentation. The second explanation was called sweep flocculation and was the catch all explanation that was used to describe observations that didn’t fit the charge neutralization explanation. Precipitation of amorphous metal hydroxide is necessary for sweep-floc coagulation. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. • The floc will then settle out in the sedimentation basin, with remaining floc being removed in the filter. Since the beginning, the objective of water treatment has not changed i.e. However, the SFmechanism has also its CN property moreover than its well-known weighting characteristic. AND Sedimentation for solids separation 6. COAGULATION 2. Submitted to: Dr. Atif Mustafa 59 (No Transcript) 60 This method allows adjustments in pH, variations in coagulant or polymer dose, alternating mixing speeds, or testing of different coagulant or polymer types, on a small scale in order to predict the functioning of a large scale treatment operation. Jar Test Procedure, Destabilization using Al(III) and Fe(III) Salts. The action differs fromprecipitation in that, prior to flocculation, colloids are merely suspended in a liquid and not actually dissolved in a solution. 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