When the filtering layer begins to clog need cleaning it, which happens every 4 to 6 weeks. The cleaning is manual and involves removing the first layer of sand, sand washing in separate tubs and in reconstruction of filter bed. Quick filters are the most used, particularly in combination with other treatments such as clarification (surface waters) and the removal of iron and manganese (deep waters), and can deal with an input flow rate 40 times higher than that of lens filters (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).
We can also make filters consist of two filter layers of materials with different specific weight (dual media). As a rule, in this case the top layer is made from anthracite, lighter, and the lower one is in quartz sand. The layer of asphalt, being formed by the coarser particles of sand, preserves the rapid occlusion of first layers of sand. After a certain time, the retained particles begin to clog the bed draining decreasing the permeability, and determining, at a constant flow rate of inflow, an increase in waters level in tanks filtering. Exceeded the limit level, the layer drained must be subjected to countercurrent washing to restore its efficiency.
The filtering layer resting on a draining bottom, which has the function of: surface filters: filtration takes place through filter cloths which prevent the passage from the materials above the size of blind holes (not es.tessuto tissue; in this case the particles are retained on the surface of filter media forming a layer of material that retains the subsequent particles.
Physical and chemical treatments normal and driven: they are divided into several phases and eliminate non-settleable suspended solids (flocculation) and correct the chemical characteristics of waters by eliminating the dissolved substances that are incompatible with the use to which the waters is bound (softening, stabilization, removal of iron, manganese, desilication, fluoridation and defluoration, aeration).
Filter volume: the filtration takes place by means of a three-dimensional porous matrix said filter bed consisting of discrete materials of small dimensions (eg. Sand); in this case the particles are retained within filter medium. The effectiveness of a filter material depends on certain properties of particles such as size, shape and surface chemistry. The filters lenses are the first filtration system used in filtration, but they are currently little used. The slow filtration can be used in case of turbidity 10 ppm.
The filters are formed from cylindrical vessels made of reinforced concrete on the bottom of which special shelves, provided with an adequate number of holes, support the filtering mass. The filter bed consists of fine sand / fine or other material minute. The filter bed is supported by an underlying layer of material, also the filter, formed by a layer of coarse gravel and the overlying layers of gravel gradually finer (mattress draining).
What lens filters the filtering action is exerted by the biological film that develops on the surface of filter in 10-15 days (aging time of filter). The film filter is very sensitive to mechanical disturbances and organic contaminants. During the period of maturation of film the filtered waters is not considered potable. The inflow of waters into filter takes place from above while runoff occurs from the bottom; the filtration rate.
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).
We can also make filters consist of two filter layers of materials with different specific weight (dual media). As a rule, in this case the top layer is made from anthracite, lighter, and the lower one is in quartz sand. The layer of asphalt, being formed by the coarser particles of sand, preserves the rapid occlusion of first layers of sand. After a certain time, the retained particles begin to clog the bed draining decreasing the permeability, and determining, at a constant flow rate of inflow, an increase in waters level in tanks filtering. Exceeded the limit level, the layer drained must be subjected to countercurrent washing to restore its efficiency.
The filtering layer resting on a draining bottom, which has the function of: surface filters: filtration takes place through filter cloths which prevent the passage from the materials above the size of blind holes (not es.tessuto tissue; in this case the particles are retained on the surface of filter media forming a layer of material that retains the subsequent particles.
Physical and chemical treatments normal and driven: they are divided into several phases and eliminate non-settleable suspended solids (flocculation) and correct the chemical characteristics of waters by eliminating the dissolved substances that are incompatible with the use to which the waters is bound (softening, stabilization, removal of iron, manganese, desilication, fluoridation and defluoration, aeration).
Filter volume: the filtration takes place by means of a three-dimensional porous matrix said filter bed consisting of discrete materials of small dimensions (eg. Sand); in this case the particles are retained within filter medium. The effectiveness of a filter material depends on certain properties of particles such as size, shape and surface chemistry. The filters lenses are the first filtration system used in filtration, but they are currently little used. The slow filtration can be used in case of turbidity 10 ppm.
The filters are formed from cylindrical vessels made of reinforced concrete on the bottom of which special shelves, provided with an adequate number of holes, support the filtering mass. The filter bed consists of fine sand / fine or other material minute. The filter bed is supported by an underlying layer of material, also the filter, formed by a layer of coarse gravel and the overlying layers of gravel gradually finer (mattress draining).
What lens filters the filtering action is exerted by the biological film that develops on the surface of filter in 10-15 days (aging time of filter). The film filter is very sensitive to mechanical disturbances and organic contaminants. During the period of maturation of film the filtered waters is not considered potable. The inflow of waters into filter takes place from above while runoff occurs from the bottom; the filtration rate.
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