Sand filter

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The cylindrical vessel built in steel is divided into three main sections:

  • Sand filtration chamber;
  • Collection chamber for the effluent filtered by the sand;
  • Backwash water storage chamber that serves the filter bed

The first filtration area contains the fine monocrystalline sand and a series of plastic diffusers on the bottom that ensure optimal drainage of the filtered water and the uniform distribution of the backwash water. The collection area of ​​the filtered effluent with sand is directly connected, through a vertical pipe, to the backwash water tank.
The backwash water storage area is calculated to contain an adequate amount of water and is systematically filled at the same height, thus ensuring homogeneous counter-washing.
The water to be filtered from the supply tower is introduced, through a distributor pipe, into the filtration chamber. Crossing the filtration area, made up of quartz sand, it reaches the collection chamber, through plastic lamellar diffusers; from here, by means of a pipe, it exits the filter and is sent for use. The filtered collection area is directly connected to the counter-washing water tank via an open duct at the top. The deposition of insoluble substances on the filter bed causes an increase in the pressure drop across it and consequently the water level slowly rises in the supply and backwash pipes.
Immediately before the water passes the upper curve of the backwash pipe, an automatic emptying system sucks the air from the pipe itself. In this way a strong suction occurs which conveys a high flow rate of water into the pipe creating a siphon which activates the backwashing of the filter.
In this way the pressure on the filter bed decays immediately and through the connection pipes the water flows from the storage compartment to the filtered collection chamber.
The water at this point moves upwards through the lamellar diffusers, the sand bed and the backwash discharge pipe. 11 filter bed is thus expanded and perfectly cleaned of the deposited solids.
This operation stops when the water level in the storage compartment drops to a level such as to defuse the siphon.
The water to be filtered flows again by gravity through the filter bed, automatically restoring filtration. The first portion of filtered water rises in the storage compartment and fills it up to the height of the drain from where the start-up for use begins again.


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