2.4.6
Media Cleaning System
The media cleaning system shall consist of a sand lift, sand washer, sand
distribution equipment and reject collection system.
2.4.6.1
Sand Lift
The sand lift shall consist of [Type 304] [Type 304L] stainless steel
eductor pipe. The pipe shall be [externally] [internally] mounted and
fixed [by welding] [by means of a [_____] ANSI gasketed flange] [_____] to
the filter vessel. Compressed air shall be supplied at [_____] to [_____]
cubic meters cubic feet per minute at [_____] Pa psig to the eductor pipe.
The suction rate shall be sufficient to result in internal recycling of the
media once every [_____] hours.
2.4.6.2
Sand Washer
**************************************************************************
NOTE: Delete cross-sectional area sizing
requirements if the sand washer unit is external to
the filter tank.
**************************************************************************
The sand washer shall be a chamber constructed of [Type 304 stainless
steel] [acrylic] [fiberglass reinforced plastic] [_____]. The washer shall
have a sloped floor to clear the sand from the bottom of the chamber. The
chamber shall have [_____] baffles attached to its walls which have a slope
sufficient to cause the descending sand to strike the opposing chamber wall
before dropping to the next level. The cross-sectional area shall be sized
to assure sufficient velocity of upflowing water to transport separated
solids into the wash chamber and out the reject pipe.
2.4.6.3
Sand Distribution Equipment
The cleaned sand shall be returned to the bed via a [sand distribution
cylinder] [sand distribution cone] [return pipe] [washbox skirt] [_____],
constructed of [fiberglass reinforced plastic] [Type 304 stainless steel]
[_____] placed and sized as shown. The sand shall be returned so that the
media will distribute evenly in a cone on top of the media bed.
2.4.6.4
Reject Collection System
The reject collection system shall consist of a stainless steel reject weir
and a [_____] diameter reject nozzle. The reject weir shall be positioned
to achieve the desired differential head between the effluent water and the
reject water. The reject collection system shall be designed to allow no
more than [2] [10] [20] [_____] percent reject water.
2.4.7
Effluent Rate Control
Filter operation shall be controlled by the liquid level in the filter tank
using a proportional, displacer-type liquid level sensor. An automatic
effluent control [globe] [ball] [_____] valve shall be provided with a
pneumatic positioner which shall regulate the degree of opening in response
to a [_____] to [_____] pneumatic signal. An increase in signal air
pressure shall increase the degree of valve opening. Flow control system
shall be self-contained and shall not require manual adjustments.
SECTION 11393
Page 23
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