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  • By Stacey Burt


    Filtration is the removal of contaminants from waters to get waters that is fit for normal domestic consumption or for irrigation of fields and also for industrial uses (eg. For use by establishments for food). With the gradual depletion of natural sources of drinking waters (deep waters), is increasingly resorting to surface waters (seas, rivers, lakes and dams) (survival water purification systems).

    These sources of supply, due to specific characteristics of waters and / or the degree of pollution, must be subjected to cycles of treatments of filtration necessary to modify the characteristics and improve its quality. Often, this happens even for the deep waters with a high content of organic substances and a high microbial contamination, especially if they are present faecal bacteria (eg. Coliforms).

    Filtration is a treatment used to remove suspended solids from the waters not sediment. Treatment consists in passing the raw waters through a filter medium (bed / filter layer or filter cloth). In case of filter layer, the filter material can be made from quartz sand, anthracite or activated charcoal. During filtration the filtered solids gradually begin to clog the filtering layer resulting in an increase of load losses, which is increased to overcome the supply pressure. Exceeded the maximum value of said pressure must be made to interruption of flow and to cleaning of filter medium.

    However, the fact that the waters is by nature a solvent makes it somewhat problematic the effective elimination of many unwanted substances. The waters is entered into a tank head from which it originated the system of waters supply - drinking. The waters containing different types of organic substances and inorganic, hereinafter classified, that must be removed during the purifying treatment. Physical treatments simple: they are articulated in a single step, eliminating the suspended solids and sediments those not coarse sediments (screening and sedimentation) and non-settleable (sieving and filtration).

    ants: the most used today are the polyelectrolytes. The agitation speed should be neither too low to prevent sedimentation of flakes, or too high to avoid breakage of flake. The slow agitation is achieved by use of mechanical mixers (dynamic system) or by placing a series of baffles in tank (static system).

    Treatments: also divided into several phases, improve the organoleptic characteristics of waters (adsorption on activated carbon) and lower the content of dissolved solids (demineralization). The interventions of this type are provided, when necessary, upstream of treatment processes of filtration real, and allow the removal of materials and substances which by their nature and size are likely to damage the equipment and compromise the efficiency of subsequent treatment stages.

    The waters containing sediments that can create several problems during the cycle of filtration. This law is valid for strictly spherical particles immersed in a liquid at rest and at constant temperature where the downward motion is not influenced neither by the presence of other particles or from the container walls.

    These flocculants, added in small doses, immediately after the coagulant, improve the efficiency of process affecting mainly. The adjuvants used are polyelectrolytes, organic macromolecules obtained through polymerization processes, waters-soluble or dispersible well, characterized by the presence of charged groups or at least polar throughout the chain.




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