The rate of head loss development using EGFM is 30% smaller than sand.
Filter runs with EGFM may be up to 50% longer than sand. Material and size specification
*Products used for the treatment of water for human consumption – silica sand and silica gravel; where products are specified by size range and maximum oversize and undersize, products for use in multi-media filters shall have maximum oversize or undersize mass fraction of 5%.
EGFM has a greater voidage than 16/30 filter sand due to it’s more angular particle shape. Greater voidage produces a more open bed structure which leads to lower headloss development.
The minimum fluidisation velocity for grade 1 EGFM in a 80 cm bed is 25m/h
The velocity for 20% bed expansion is 40 m/h.
In practice the backwash velocities required for Grade 1 EGFM are the same as sand
The use of air scour prior to backwash is recommended with an air flow rate of 50 to 80m3/hr/m2
The Waste and Resources Action Programme (WRAP) works with local authorities, business and households to prevent waste, increase recycling and develop markets for recycled and sustainable products. The reports in this section analyse the use of recycled glass as a filtration medium.
WRAP Report 1 – Full Scale Operational Trials Involving The Use of Recycled Glass in Selected Markets.