Literature Review On Coagulation

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Literature Review
Coagulation and flocculation processes are essential in a number of diverse disciplines including biochemistry, rubber manufacturing and in water and wastewater treatment (Bratby, 2006). These processes are typically used in destabilizing, agglomerating and subsequent removal of particles. Coagulation is a physico-chemical process which neutralizes the colloidal particles in water by a chemical called coagulant. The neutralization forces the colloidal particles to join together to form small aggregates called flocs which are easily filtered from the water.
The widely used coagulants in water treatment are metal salts including aluminium sulphate , aluminium chloride , polyaluminium chloride , ferric sulphate and ferric chloride (Saunders and Saunders, 1991). The primary mechanisms by which coagulant can remove both organic and inorganic contaminants from water include colloid destabilization, precipitation and co-precipitation (Langelier and Ludwig, 1949; Randtke, 1988; Saunders and Saunders, 1991). Mer and Healy(1963) deplored the indiscriminate use of the terms coagulation and flocculation which is found to represent synonymous concepts. It was proposed that the term coagulation be based on colloidal destabilization where colloidal particles
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The recycle sludge process has advantages over the conventional process because it produces a much denser sludge due to the “seeding” effect of the precipitates in the recycled sludge (Streeter et al., 1971). Seeding is commonly used in the metallurgical fields to allow precipitation products to grow and become larger in size. The nature of the precipitate formed in the presence of the seed crystals is known to be influenced to a large extent by the seed crystal size, seed crystal amounts and agitation rate (Streeter et al.,
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