The three most used materials are: sand, used in filtration, is a natural material, silica, from rivers, natural deposits, dunes or obtained from marine pebbles. Its actual density is from about 2.5 to 2.7. Sharp sand is obtained by a career flint grinding or sea pebbles, followed by washing, drying and sieving. It presents angular grains, favor the retention of particles during the filtration (portable water purifiers for survival).
Rolled sand is a natural sand, sifted after washing and drying. Unlike the sharp sand, it has rounded grains, and exists in a grain size range, that is to say of dimension sand, smaller. Anthracite, carbon-based material obtained by calcination of plant material such as wood or peat. It is in form of hard and angular grains. Its actual density is of order of 1.45 to 1.75;
The waters seeps through the network inside the cylinder and is sent to subsequent treatments, while the material is retained on its surface.
These sources of supply, due to specific characteristics of waters and / or the degree of pollution, must be subjected to cycles of treatments of purification 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).
Stokes' law is valid for spherical particles whose size does not exceed 0.1 mm. As a first approximation, it is applied to any sedimentary particles of small size (sand, silt, clay). One of simplest techniques for settling is static settling for example with a vertical clarifier. Power is supplied from the bottom, the particles sediment and may be recovered at the bottom of cone, while the treated waters is discharged from the top by overflow. The sedimentation rate is unfortunately generally low.
The primary sedimentation uses the force of gravity for removing the solid sediments predominantly inorganic (sand, loam, silt, etc.). It is adopted as pretreatment physical limited to waters with high turbidity (1,000 mg / l) and / or with silica in suspension. In these cases, is inserted upstream of flocculation in order to lighten the load coming.
The screening aims to retain coarse solids non settleable (branches, leaves, rags, plastic, etc.) And solid coarse sediment (gravel, etc.). Among these materials Coarse including the possible fauna of waters body (fish). The grilling is adopted in all the patterns of surface waters treatment, and in this case is placed upstream of other treatments.
For waters of Category A1, may be the only physical treatment in addition to disinfection. The grid consists of series of metal bars placed at a distance such as to create obstacles to coarse bodies carried by the current. The grid is installed internally to channel coming to system, inclined with a slope generally equal to 1: 3.
Rolled sand is a natural sand, sifted after washing and drying. Unlike the sharp sand, it has rounded grains, and exists in a grain size range, that is to say of dimension sand, smaller. Anthracite, carbon-based material obtained by calcination of plant material such as wood or peat. It is in form of hard and angular grains. Its actual density is of order of 1.45 to 1.75;
The waters seeps through the network inside the cylinder and is sent to subsequent treatments, while the material is retained on its surface.
These sources of supply, due to specific characteristics of waters and / or the degree of pollution, must be subjected to cycles of treatments of purification 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).
Stokes' law is valid for spherical particles whose size does not exceed 0.1 mm. As a first approximation, it is applied to any sedimentary particles of small size (sand, silt, clay). One of simplest techniques for settling is static settling for example with a vertical clarifier. Power is supplied from the bottom, the particles sediment and may be recovered at the bottom of cone, while the treated waters is discharged from the top by overflow. The sedimentation rate is unfortunately generally low.
The primary sedimentation uses the force of gravity for removing the solid sediments predominantly inorganic (sand, loam, silt, etc.). It is adopted as pretreatment physical limited to waters with high turbidity (1,000 mg / l) and / or with silica in suspension. In these cases, is inserted upstream of flocculation in order to lighten the load coming.
The screening aims to retain coarse solids non settleable (branches, leaves, rags, plastic, etc.) And solid coarse sediment (gravel, etc.). Among these materials Coarse including the possible fauna of waters body (fish). The grilling is adopted in all the patterns of surface waters treatment, and in this case is placed upstream of other treatments.
For waters of Category A1, may be the only physical treatment in addition to disinfection. The grid consists of series of metal bars placed at a distance such as to create obstacles to coarse bodies carried by the current. The grid is installed internally to channel coming to system, inclined with a slope generally equal to 1: 3.
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