1. Filtration Precision

• Ultrafiltration (UF): Uses a membrane with a larger pore size, typically in the range of 0.01 to 0.1 microns. It effectively removes suspended solids, bacteria, viruses, and high-molecular-weight organic compounds.

• Reverse Osmosis (RO): Uses a much denser, semi-permeable membrane with an extremely small pore size, approximately 0.0001 microns. It is designed to remove virtually all dissolved salts, minerals, and organic molecules.

2. Operating Pressure

• UF: Operates at relatively low pressure (typically 1-10 bar or 15-145 psi). It relies mainly on size exclusion.

• RO: Requires much higher pressure (typically 15-85 bar or 200-1200 psi) to overcome the natural osmotic pressure and force water through the dense membrane.

3. Removal Capabilities

• UF: Removes particles, turbidity, colloids, most bacteria and viruses, and large organic molecules. It does NOT remove dissolved salts, minerals (like calcium, magnesium, sodium), or low molecular weight organics.

• RO: Removes over 95-99% of all dissolved solids, including salts, minerals, heavy metals (like lead, arsenic), fluoride, nitrates, and all bacteria and viruses. It produces highly purified water.

4. Wastewater Production

• UF: Produces little to no wastewater. The backwash water used for cleaning is the only waste stream, which can often be recovered.

• RO: Produces a significant wastewater or brine stream (often called “concentrate”). For every gallon of purified water produced, an RO system may discharge 1 to 4 gallons of wastewater, depending on its efficiency.

5. Energy Consumption

• UF: Requires less energy due to lower operating pressures.

• RO: Requires significantly more energy to power the high-pressure pumps.

6. Applications

• UF:

  • Pre-treatment for RO systems.

  • Clarification of fruit juices and beverages.

  • Separation of oil/water emulsions.

  • Production of potable water from relatively clean sources (removing pathogens).

• RO:

  • Desalination of seawater and brackish water.

  • Production of high-purity water for pharmaceuticals, laboratories, and semiconductor manufacturing.

  • Drinking water purification (removing salts, contaminants, and improving taste).

  • Food and beverage concentration.

  • Wastewater treatment and reuse.

7. Mineral Retention

• UF: Retains beneficial minerals (like calcium and magnesium) in the water.

• RO: Removes almost all minerals, resulting in demineralized water. This water is often “remineralized” in drinking water applications for taste and health reasons.

Summary Table

Simple Analogy

• Ultrafiltration is like an extremely fine sieve that blocks sand and pebbles but lets dissolved sugar and salt pass through.

• Reverse Osmosis is like a super-fine filter that is designed to block even the dissolved sugar and salt molecules, allowing almost only pure water to pass.

In many industrial and commercial systems, UF is used as a pre-treatment step for RO to protect the more sensitive and expensive RO membranes from fouling.