Which filter has an unstratified media distribution?

Which filter has an unstratified media distribution?

• A. Slow sand filters
• B. Rapid sand filters
• C. High-rate filters
• D. Dual-media filters

Answer: (A)

Media distribution in a filtration bed describes how the filter media are arranged by particle size. An unstratified distribution means there is no deliberate layering by size; the bed is made of a single, uniform material. Slow sand filters use a uniform layer of fine sand, often with a biological surface layer called the schmutzdecke that forms on top. Because the media beneath isn’t layered by size, the distribution is unstratified. Other filter types are designed with layered media to support higher filtration rates—for example, a top layer of coarse material over finer sand or multiple media like anthracite over sand over gravel—so they are stratified. Therefore, the unstratified case corresponds to slow sand filtration.

Media distribution in a filtration bed describes how the filter media are arranged by particle size. An unstratified distribution means there is no deliberate layering by size; the bed is made of a single, uniform material. Slow sand filters use a uniform layer of fine sand, often with a biological surface layer called the schmutzdecke that forms on top. Because the media beneath isn’t layered by size, the distribution is unstratified. Other filter types are designed with layered media to support higher filtration rates—for example, a top layer of coarse material over finer sand or multiple media like anthracite over sand over gravel—so they are stratified. Therefore, the unstratified case corresponds to slow sand filtration.