What characterizes the filter media in a dual media filter?

The filter media in a dual media filter is characterized by a layer of anthracite on top of sand. This configuration is specifically designed to optimize the filtration process. The anthracite, being a lighter material, covers the sand, which typically has a finer grain. This arrangement allows for improved depth filtration, as the larger particles are trapped in the anthracite layer while the smaller particles are filtered through the sand below.

The dual media system enhances the overall filtration efficiency by allowing for a greater effective filtration area and a reduced risk of clogging compared to using a single type of media. The combination of different materials with varying sizes and densities is what sets this type of filter apart, making it effective in treating drinking water by capturing a broad range of contaminants.

In contrast, using only different sizes of sand would limit the filtration capabilities, while a combination of sand and gravel does not utilize the benefits of having a lighter top layer for enhanced filtering. A singular media type would not provide the layered filtration benefits seen in dual media systems, making the anthracite-sand combination the optimal choice for effective water treatment.