Monomedium filters are best suited for which filtration approach?

• A. Direct filtration
• B. Slow filtration
• C. Rapid filtration
• D. High-rate filtration

Answer: (A)

Monomedium filters use a single layer of uniform media, typically sand, which suits a direct filtration setup where coagulation and flocculation have already formed settled flocs and only a single-pass filtration is needed. The uniform depth and predictable pore structure of a monomedium bed efficiently trap those flocs without the complexity of multi-layer media, keeping operation simple and cost-effective. Because the process relies on a straightforward filtration step after chemical pretreatment, headloss remains manageable and backwashing is straightforward, which is ideal when turbidity is moderate and a settling basin isn’t used ahead of filtration. In contrast, slow filtration depends on a deeper, biologically active bed for extended contact; rapid high-rate filtration benefits from multiple media layers to optimize removal at higher loading. The single-media approach doesn’t provide those benefits, so it’s best for direct filtration.