Granular filtration

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The filter sand, consisting of 99.5% SiO2, is extremely low in trace metals and polycyclic aromatic hydrocarbons. This makes our filter sand the best sand available for monitoring well systems.

In water treatment, granular filtration is a process where water flows through granular material (often sand) while suspended solids (sand, clay, iron and aluminum flocs) are retained, substances are biochemically decomposed and pathogenic microorganisms (bacteria, viruses, protozoa) are removed.

Granular media, rapid rate filters and filter media

Granular, high-density carbon.
Filter sand, supplied in bags and pallet packages. It consists of 99.5% SiO2 and is extremely low in trace metals and polycyclic aromatic hydrocarbons. This makes our filter sand the best sand available for monitoring well systems. Photo: Eijkelkamp Agrisearch Equipment BV.
Type Of Filtration Media Availability Ease of Use Effectiveness Cost
Granular media, rapid rate depth filter Sand, gravel, diatomaceous earth, coal, other minerals High Easy to Moderate Moderate* (depends on microbe size and pre-treatment) Low to moderate
Slow sand filter Sand High Easy to moderate (community use) High** in principle but often low in practice Low to moderate
Vegetable and animal derived depth filters Coal, sponge, charcoal, cotton, etc. Medium to high Moderate to Difficult Moderate* Low to moderate
Fabric, paper, membrane, canvas, etc. filter Cloth, other woven fabric, synthetic polymers, wick siphons Varies: some low; others high Easy to moderate Varies from high to low (with pore size and composition) Varies: low for natural; high for synthetics
Ceramic and other porous cast filters Clay, other minerals Varies: high- low, with materials availability and fabrication skill Moderate. Must be physically cleaned on a regular basis to prevent clogging and biofilm growth Varies from high to low (with pore size and ceramic filter quality) Moderate to high
Septum and body feed filters Diatomaceous earth, other fine media Varies Moderate to difficult; dry media a respiratory hazard Moderate Varies
*Moderate typically means 90-99% reductions of larger pathogens (helminth ova and larger protozoans) and solids-associated pathogens, but low(<90%) reductions of viruses and free bacteria, assuming no pre-treatment. With pre-treatment (typically coagulation), pathogen reductions are typically >99% (high).
**High pathogen reduction means >99%.

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