Which filter type uses a semi-permeable membrane to remove dissolved substances from water?

• A. Reverse Osmosis Filter
• B. Centrifugal Filter
• C. Self-Cleaning/Flushing Filter
• D. Filter Accessories

Answer: (A)

The key idea is removing dissolved substances using a barrier that only lets certain molecules pass. This is how a reverse osmosis system works: water is forced through a semi-permeable membrane that allows water molecules to pass but blocks most dissolved salts, minerals, and other contaminants. By applying pressure, the clean water (permeate) moves through, while the concentrated dissolved substances stay behind or are flushed away as concentrate. This capability to separate dissolved substances relies specifically on the membrane’s selective permeability, which is why this method is the best match.

In contrast, other options rely on different principles. A centrifugal-type filter uses rotation to separate particles by size, catching suspended solids rather than dissolving substances. A self-cleaning or flushing filter is typically a screen or cartridge filter that traps particulates but doesn’t remove dissolved ions. Filter accessories are components rather than a filtration process.