Tennessee Wastewater Operator Practice Exam

Which filtration technique is specifically used for very small particulate removal?

1. Reverse osmosis

2. Microfiltration

3. Ultrafiltration

4. Air filtration

The correct answer is: Reverse osmosis

Reverse osmosis is specifically used for very small particulate removal, including dissolved salts and other impurities. This technique employs a semi-permeable membrane that allows water molecules to pass through while rejecting a wide range of contaminants. The high pressure applied to the feed water facilitates the movement of water through the membrane, effectively removing particles, bacteria, sugars, and ions, yielding high-quality effluent. The other filtration techniques, while effective in their respective applications, do not target particulates at the same microscopic level as reverse osmosis. Microfiltration targets larger particles and bacteria, usually in the range of 0.1 to 10 micrometers, while ultrafiltration fills the gap between microfiltration and reverse osmosis, dealing with particles in the range of 1 to 100 nanometers but not effectively removing dissolved solids. Air filtration is focused on removing particulate air contaminants and is not applicable in this context. Thus, reverse osmosis stands out as the technique specifically aimed at very small particulate removal.