The first applications by mankind of using sand to filter water or beverages is lost in antiquity. We have records that Roman engineers built aqueducts to bring clear water from mountain springs through beds of sand to fill city fountains for drinking and bathing. With the abundance of natural zeolite mineral formations in Italy, it would not be surprising if it was zeolite sand that was used to filter water for some of their fountains.

During the Medieval Period, Europe was decimated several times by disease. The severity of typhoid fever and cholera epidemics could have been reduced if not eliminated with proper water treatment. By the mid 19th Century it was demonstrated that those that drank tea (thereby boiling water) were less prone to certain diseases. Until that time, it was believed that disease was spread by foul odors (“vapours”). Slow sand filters for drinking water were constructed in London, England by 1829 with a three foot deep sand bed. Sand filters were in use in the United States by the late 19th Century. By the 20th Century water systems implementing sand filtration for community drinking water were common.

The science of filtration has progressed exponentially in the last one-hundred years. We can now filter sea water with synthetic membranes by reverse osmosis to remove ions of sodium and chloride to make drinking water. We have available for our use nano-filtration, ultra-filtration and micro-filtration using manmade fabrics, membranes and hollow fibers. Electrodialysis Reversal can use electrical current to remove dissolved solids including low-atomic number ions from water. Still the majority of filtration applications call for inexpensive gravity or pressure filtration through granular media. In fact, the sub-micron filter systems still need suspended solids removal ahead of them to avoid fouling of the membranes.

Silica Sand

Silica sand has been the mainstay of granular filtration in potable water systems as well as for swimming pools and ponds to filter out particles down to 20 microns. Sand is ubiquitous and inexpensive.

The alternative Zeobrite® media is now available through widespread distribution for swimming pool and potable water systems. Zeobrite® can be used in simple filtration vessels manufactured for silica sand but Zeobrite® has properties that permit a higher quality of filtration. Zeobrite® has over 100 times the surface area of silica sand. It is a microporous media with millions of small pore spaces for entrapment of contaminant particle size from silt to colloids. The Zeobrite® granules are hard enough to last several years (recommended 4 to 5 years ) in a high-rate pressurized system with up to 20 gpm/ft2 backwash rate.