Which filtration media are commonly used?

• A. Gravel only
• B. Sand and anthracite
• C. Activated carbon only
• D. Copper piping

Answer: (B)

Filtration media involve layers that physically remove particles as water passes through. The most common arrangement is a dual-media bed of sand and anthracite. Anthracite sits on top because its larger, more porous grains create good flow characteristics while catching bigger debris. Below it, sand provides a finer filtration layer that traps smaller particles. This combination balances high filtration efficiency with reasonable head loss, making it widely used in many treatment setups.

Gravel is typically used as a support layer to ensure even distribution and prevent media loss, not as the main filtration medium. Activated carbon is used mainly for adsorption of dissolved substances like organics and tastes/odors, rather than for particulate filtration in a standard filter bed. Copper piping, on the other hand, is a material for conveying water, not a filtration medium.