What is the difference between an UF membrane and an RO membrane?
Pore Size
- UF Membrane: The pore size of UF membrane is relatively larger,
generally ranging from 0.01 to 0.1 micrometers.
- RO Membrane: RO membrane has much smaller pores, which is about
0.0001 micrometers, just one millionth of the diameter of a human
hair.
Filtration Level
- UF Membrane: It can remove larger particles, colloids, bacteria,
and some viruses, but may not be as effective in removing dissolved
ions and smaller contaminants. For example, it cannot completely
remove dissolved salts and heavy metals.
- RO Membrane: It can achieve a very high level of purity by
removing a wide range of contaminants, including dissolved salts,
heavy metals, bacteria, viruses, and organic compounds, with
removal rates of up to 99% for many substances.
Membrane Type
- UF Membrane: It is usually made of porous polymer materials. The
filtration process mainly relies on physical sieving to separate
particles and molecules based on size exclusion.
- RO Membrane: Composed of a thin film composite with multiple
layers, which is designed to have selective permeability, allowing
only water molecules to pass through while blocking dissolved
solids and other impurities.
Pressure Requirement
- UF Membrane: Operates at relatively low pressures, typically
ranging from 5 to 50 psi, making it more energy-efficient.
- RO Membrane: Requires much higher operating pressures, usually
ranging from 50 to 1200 pounds per square inch (psi), to force
water through the semi-permeable membrane.
Mineral Retention
- UF Membrane: Generally retains minerals and other dissolved
substances in the water because of its larger pore size, which
helps maintain the nutritional quality and taste of drinking water.
Application Fields
- UF Membrane: Commonly used in applications where the removal of
larger particles and some microorganisms is sufficient, such as
pre-treatment for reverse osmosis systems, industrial water
recycling, and some household water purification systems where a
lower level of purification is acceptable.
- RO Membrane: Widely used in applications that require high-purity
water, such as drinking water purification, pharmaceutical
manufacturing, electronics production, and seawater desalination.
