Filtration of water is the most traditional type of water treatment. Filtralite has the ideal properties to work as a good filter media in both single- and dual media filters for filtration of coagulated water.
In dual media filters Filtralite has proved to be as good as, or better than, comparable media. By replacing the most traditional top layer filter material, anthracite, with Filtralite, time between backwashes can be increased by about 25%. This means fewer stops for backwash and reduced use of backwash water, resulting in more stable water quality and lower operational costs.
An even better filter performance can be obtained by also replacing the sand in the bottom layer with Filtralite. The so called Filtralite Mono-Multi filter, consisting of a bottom layer of heavy Filtralite and a top layer of light Filtralite, gives extremely low head loss and good water quality. Due to the low density of both layers, the water velocity needed for backwash is much lower than for filters using sand as bottom layer.
Filters with Filtralite can be operated within a large range of filtration rates. The filtration rate will always be dependent of the configuration of the filter and the treatment process. Existing Filtralite filters operate from about 2 m/h up to around 30 m/h.
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Biological filtration
. In biological filters bacteria attach to the filter media and a Biofilm arises on the surfaces of the filter grains. A large available surface area for Biofilm growth is one of the most essential properties of filter media used in Biofilm processes. The crushed Filtralite grains have a large surface area, resulting in Filtralite being an ideal media for use in biological treatment processes.
Tests have shown that Filtralite is as good as or better than alternative carrier materials for biological treatment of drinking water. Ammonia, iron, manganese and other biodegradable substances can be effectively removed in biological treatment using Filtralite as a carrier media.
An important factor for an efficient biological treatment process is the time the water is in contact with the Biofilm. The most common way to quantify the contact time is the Empty Bed Contact Time (EBCT), which is defined as the time the water needs for passing through the entire filter volume. The needed EBCT vary for different water qualities and treatment systems, but about 20 minutes is quite normal in many systems. To be able to define the correct EBCT for a specific system it is recommended to run a pilot test. Existing Filtralite biofilters operate with filtration rates up to about 30 m/h.
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