Dual Media Filter (DMF)

In dual media filtration, part of the fine sand is replaced by a layer of lighter material (anthracite) with an effective grain size greater than that of the sand to avoid the screening effect of the finest grains of sand and promote the penetration of impurities throughout the entire depth of the filter.The grain size of each layer is so selected that they undergo similar expansion with the same flow of wash water thus enabling them to be reclassified at the end of each washing.

This allows distribution of the retained suspended solids. The coarsest are retained in the upper layer composed of large grains, while the lower fine-grained layer performs a polishing process.