Water Treatment

ClarificationThe suspended matter can consist of large solid, settleable by gravity alone without any external aids, and non-settleable material, often colloidal in nature.  ?Steps of ClarificationCoagulation    Reduction of the surface charge of suspended solids and, reduction of forces of mutual repulsion results in the agglomeration of the particles. Flocculation The addition of a relatively small quantity of flocculating agent, consist of polymer of long chain containing active groups results in the agglomeration of the individual particles. Floc formation Impurities suspended and dissolved in the water can be converted to forms suitable for sedimentation, floatation or filtration by addition of appropriate additives. Adsorption Hydroxides of  Fe2+ , Fe3+ , Al3+ process a very voluminous structure, which offers a large number of adsorption points for impurities. PrecipitationPrecipitation is effected by the additional precipitations that react with substances contained in the water to form precipitates of low solubility. ?ClarifierSuspended matter in raw water supplies is removed by coagulation, flocculation and sedimentation, often referred to as conventional clarification. Finely divided particles suspended in surface water repel each other because their surfaces are predominantly negatively charged. Coagulation is to neutralize charges to destabilize suspended solids. Flocculation is the process of bringing together the destabilized or coagulated particles to form a larger agglomeration or flocculation.  Sedimentation refers to the physical removal from suspension or setting that occurs once the particles have been coagulated and flocculated. FiltrationFiltration is a separative process widely used for the removal of particles from fluid whether these are gases or liquids, and usually considered a simple mechanical process, actually involves the mechanisms of adsorption, straining, sedimentation, interception, diffusion, and inertial compaction.  ?Pressure Sand FilterThe pressure filter comprises a cylindrical steel pressure vessel, lined with rubber, containing a bed of specially graded sand supported on layers of graded pebbles. As the underground water flows downward through the filter suspended solids are retained on the sand bed. When the filter is in operation solid will gradually accumulate on the filter bed and in consequence the pressure loss across the filter will also increase. The filter must be cleaned when the pressure loss has risen about 0.5kg/cm2. The filter is cleaned accumulated solids by an upward flow of underground water.AdsorptionAdsorption is an interfacial occurrence in water contents usually between liquid and solid. It occurs from the attraction between oppositely charged sites residence on the atoms of the adsorbent.  ?Activated Carbon FilterGranular activated carbon(GAC), widely employed for its adsorptive quantities, comes from many sources. The activated carbon granules are highly porous. The adsorptive properties for specific molecules are believed to be governed by the pore size and shape.