Microfiltration sits between ultrafiltration and multimedia filtration based on pore size. Which option correctly lists those adjacent stages?

Microfiltration sits between ultrafiltration and multimedia filtration based on pore size. Which option correctly lists those adjacent stages?

• A. Nanofiltration and Reverse Osmosis
• B. Ultrafiltration and Multimedia Granular Filtration
• C. Multimedia Granular Filtration and Nanofiltration
• D. Ultrafiltration and Nanofiltration

Answer: (B)

The core idea is that filtration stages are arranged by pore size from largest to smallest, so each step removes progressively smaller particles. Multimedia granular filtration uses very coarse media with large pore spaces, which handles larger suspended solids. Microfiltration then follows, with membranes that have smaller pores (roughly 0.1 to 10 micrometers), so it can remove smaller particles and some bacteria while letting most dissolved substances pass. After microfiltration comes ultrafiltration, which has even smaller pores (about 0.01 to 0.1 micrometers) and targets smaller macromolecules and colloids. Nanofiltration and reverse osmosis are finer still, removing even smaller solutes. So the stages adjacent to microfiltration by pore size are multimedia granular filtration on the larger-pore side and ultrafiltration on the smaller-pore side. The other options don’t pair the neighboring stages correctly, since they mix stages that are both larger or both smaller than microfiltration or don’t flank MF.

The core idea is that filtration stages are arranged by pore size from largest to smallest, so each step removes progressively smaller particles. Multimedia granular filtration uses very coarse media with large pore spaces, which handles larger suspended solids. Microfiltration then follows, with membranes that have smaller pores (roughly 0.1 to 10 micrometers), so it can remove smaller particles and some bacteria while letting most dissolved substances pass. After microfiltration comes ultrafiltration, which has even smaller pores (about 0.01 to 0.1 micrometers) and targets smaller macromolecules and colloids. Nanofiltration and reverse osmosis are finer still, removing even smaller solutes.

So the stages adjacent to microfiltration by pore size are multimedia granular filtration on the larger-pore side and ultrafiltration on the smaller-pore side. The other options don’t pair the neighboring stages correctly, since they mix stages that are both larger or both smaller than microfiltration or don’t flank MF.