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Solids, suspended solids and colloids removal units


Refining filters "AKPA"

General information

Refining is the process where the water or waste left after the sedimentation or coagulation treatment, flows through a tank filled with the appropriate medium in order to remove any remaining colloids or suspended solids. Refining is an efficient, quick and optimum water purification method. The porous material which is used can be sand, activated carbon, anthracite or granite.

ATHANASIOS KOUTSOUKOS S.A. undertakes the studying and construction of refining filters for the removal of solids, suspended solids and colloids.

filter anthracite graphite sand activated carbon

Process description

Refining is a complicated process and it is achieved via one or more of the following mechanisms:filter anthracite graphite sand activated carbon

  1. Biological oxidation with the help of the organic substrate which develops in the surface of the sand.
  2. Sedimentation within the tiny spaces between the grains of sand
  3. Desorption through the “Bravais” lattice of the used media
  4. Restraint via the adhesion in the surface of the media with the formed ionic bonds.


Backwash is necessary in order to “clean” the filter as the retained suspended solids and colloids will block the filter. The backwash circle will automatically start when a pressure difference between the inlet and the outlet occurs. Δp controllers are installed in the inlet and outlet in order to monitor the pressure.

The size of the filter depends upon the concentration of the suspended and dissolved solids, the type and the quantity of the media as well as from other parameters. The filters are made of steel or stainless steel or from resistant polymers. The inlet for the water or waste water is situated in the top part of the filter and the outlet is at the bottom part of the filter. The filters are equipped with several automatic valves, Δp controllers as well as other instruments that monitor and ensure the refining. In addition the filters fulfill the instructions PED ΕΕ97/23 for pressurized equipment and it is accompanied by certificate CE.