Placement

The general procedure for the placement of filter media is described below, which forms the bases of the technical content of a site specific method statement.

Pattern Test
*	This is carried out by the client prior to the installation of the media to check the filter floor's condition. The water used for this test [150 mm] may be left in the filter ready for the installation of the gravel.
Gravel Installation
*	The gravel will be delivered to site in tote bags and brought to the filter pump by forklift truck. In the filter the gravel will be spread over the filter floor by an operator. The water left in the filter will serve two purposes.
	1	To provide water, via a submersible pump, for the filter media pump
	2	To cushion the placement of the gravel into the filter and protect the nozzles.
*	The layer of gravel is then leveled by hand working back to the exit ladder to ensure no footprints are left in the filter.
*	A further pattern test may now be done by the client to check that all the nozzles are in situ and that none have been broken. Again the water may be left in the filter ready for the installation of the sand.
Sand Installation
*	The sand may be delivered to site either in tote bags or by bulk tipper lorry. By accepting delivery in bulk the financial and environmental costs of the providing bags is eliminated.
*	The sand is pumped into the filter. The quantity required has been determined by calculation. The sand is placed approximately level in the filter
*	The sand layer is now backwashed clean by the client. During the start of the process the sand filter media will liquefy and level itself. Air scouring a bed, without backwashing, will not completely level a layer of filter media
*	The filter bed is now completely drained. Partly drained beds may be up to 5% thicker resulting in incorrect bed levels.
*	The fines from on top of the smooth sand layer are now removed by hand and placed into a tote bag ready for disposal off site. Approx 12mm of sand will be removed.
*	The sand level is checked and if required topped up with available sand in tote bags.
Anthracite Installation
*	Anthracite filter media will be delivered to site in tote bags
*	The anthracite is pumped into the filter to the required level [by calculation]
*	The anthracite is now backwashed clean by the client during which the layer will level itself.
*	The anthracite level is checked and if required topped up.