Glass sand as water filtration system have below advantage :

Save Water: Glass Pearls spherical smooth shape results in a low coefficient of friction, reducing its backwash water requirements. 

High Purity: Glass Pearls are manufactured from pure glass which are chemically inert. Glass Pearls have been independently lab tested for leeching contaminants and found to be well within Australian Drinking Water Guidelines.

Safe and Smooth:Glass Pearls are spherical and do not have any sharp edges. They are safe to handle. 

Time Saving: Its high purity means very little backwashing is required to cleanse the filter media, prior to commissioning the filter.

Superior Clarity: Glass Pearls have been laboratory tested to be able to effectively filter down to below 3 microns. 

Size: 0.1-0.3mm; 0.3-1.25mm; 1.25-2.50mm, 2.50-4.00mm etc. ,other sizes are available as per requirement.