Media Support Systems

As part of the installation of plastic cross-flow media, Plastic Media Engineering Ltd supply and install the filter bed floor under-drainage to suit.

Plastic cross-flow media requires a minimum of 25% supporting area beneath the media which, is achieved using medium density (7 Newton) concrete blocks laid without grout directly onto the filter bed floor.

For media bed depths up to 3.6m the blocks are laid in rows on maximum centres of 800mm using 450mm long x 225mm wide x 100mm high blocks. (To give 100mm of space between base of media and tank floor)

For media bed depths over 3.6m the blocks are laid in rows on maximum centres of 800mm using 450mm long x 225mm wide x 100mm high blocks x 2 blocks high. (To give 200mm of space between base of media and tank floor)

These configurations are also dependent on process application i.e. maximum flow rates and ventilation requirements beneath the media.

The filter bed floor is usually configured as (a) conical shape or (b)’bent penny’ shape with an outlet gully running along the diameter.

For (a) the support blocks are laid out like spokes of a wheel to ensure drainage to the centre of the filter.

For (b) the support blocks are laid out in parallel lines at right angles to the gulley. The tank floor should have a minimum gradient of 1 in 100 and a maximum of 1 in 50.

a. FILTER BED FLOOR UNDERDRAINAGE – ‘CONICAL SHAPE’

b. FILTER BED FLOOR UNDERDRAINAGE – ‘BENT PENNY’

c. FILTER BED FLOOR UNDERDRAINAGE – CONCRETE LINTELS ON DWARF WALLS