If there is no pretreatment, what membrane processes will remove dissolved organic matter?

• A. Microfiltration and nanofiltration
• B. Nanofiltration and reverse osmosis
• C. Microfiltration and ultrafiltration
• D. Nanofiltration and ultrafiltration

Answer: (B)

When targeting dissolved organic matter, the membrane needs to reject small dissolved molecules, not just particles. Microfiltration and ultrafiltration mainly remove suspended solids and larger colloids; dissolved organics pass through because their molecules are too small or not sufficiently excluded by those pore sizes. Nanofiltration and reverse osmosis, on the other hand, provide much tighter barriers that reject most dissolved organic compounds due to their small effective pore sizes and charge-based rejection. So, without pretreatment, nanofiltration and reverse osmosis are the membrane processes capable of removing dissolved organic matter.