RO & Nanofiltration Glossary: Essential Terms Defined

This glossary covers key terms related to pressure-driven membrane processes. Each term is defined with technical accuracy for membrane researchers, engineers, and water treatment professionals. For the complete glossary covering all 80+ membrane technology terms, see our comprehensive membrane technology glossary.

Pressure-Driven Membrane Processes

Reverse Osmosis (RO)

A high-pressure membrane separation process that uses a semi-permeable membrane to remove dissolved salts, organics, and other solutes from water. RO operates by applying pressure greater than the osmotic pressure of the feed solution, forcing pure water (permeate) through the membrane while rejecting contaminants. It is widely used in desalination, ultrapure water production, and wastewater reclamation. Tech Inc. supplies flat sheet and crossflow test cells optimised for evaluating RO membrane performance.

Nanofiltration (NF)

A membrane process operating between reverse osmosis and ultrafiltration, typically rejecting multivalent ions and organic molecules with molecular weights above 200–1000 Da. NF membranes carry a surface charge, making them effective for selective ion separation and water softening. They operate at lower pressures than RO, reducing energy costs while still achieving high rejection of divalent salts.

Ultrafiltration (UF)

A low-pressure membrane process that separates suspended solids, colloids, bacteria, and macromolecules from water using membranes with pore sizes ranging from 0.01 to 0.1 micrometres. UF is commonly used as a pre-treatment step for RO systems and in the food, dairy, and pharmaceutical industries. Tech Inc. offers UF membrane test cells and sampling stations ideal for pilot-scale UF evaluations.

Microfiltration (MF)

A membrane separation process using membranes with pore sizes between 0.1 and 10 micrometres to remove suspended particles, bacteria, and large colloids from feed streams. MF operates at very low transmembrane pressures and is frequently used for pre-treatment, clarification, and sterilisation in water treatment and beverage production.

High-Pressure Reverse Osmosis (HPRO)

A specialised RO process that operates at pressures exceeding 80 bar, designed for treating high-salinity brines and achieving maximum water recovery. HPRO is used in zero-liquid discharge (ZLD) systems, mining wastewater treatment, and concentrate management. Tech Inc. high-pressure test cells are engineered to withstand these demanding operating conditions.

Loose Nanofiltration

A subcategory of nanofiltration membranes that exhibit higher permeability and lower rejection than tight NF membranes. Loose NF is used for selective removal of organic micropollutants while allowing monovalent salts to pass through, making it useful in pharmaceutical separations and dye removal from textile wastewater.

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Frequently Asked Questions

What is Reverse Osmosis (RO)?

A high-pressure membrane separation process that uses a semi-permeable membrane to remove dissolved salts, organics, and other solutes from water. RO operates by applying pressure greater than the osmotic pressure of the feed solution, forcing pure water (permeate) through the membrane while rejecting contaminants. It is widely used in desalination, ultrapure water production, and wastewater reclamation. Tech Inc. supplies flat sheet and crossflow test cells optimised for evaluating RO membrane performance.

What is Nanofiltration (NF)?

A membrane process operating between reverse osmosis and ultrafiltration, typically rejecting multivalent ions and organic molecules with molecular weights above 200–1000 Da. NF membranes carry a surface charge, making them effective for selective ion separation and water softening. They operate at lower pressures than RO, reducing energy costs while still achieving high rejection of divalent salts.

What is Ultrafiltration (UF)?

A low-pressure membrane process that separates suspended solids, colloids, bacteria, and macromolecules from water using membranes with pore sizes ranging from 0.01 to 0.1 micrometres. UF is commonly used as a pre-treatment step for RO systems and in the food, dairy, and pharmaceutical industries. Tech Inc. offers UF membrane test cells and sampling stations ideal for pilot-scale UF evaluations.

What is Microfiltration (MF)?

A membrane separation process using membranes with pore sizes between 0.1 and 10 micrometres to remove suspended particles, bacteria, and large colloids from feed streams. MF operates at very low transmembrane pressures and is frequently used for pre-treatment, clarification, and sterilisation in water treatment and beverage production.

What is High-Pressure Reverse Osmosis (HPRO)?

A specialised RO process that operates at pressures exceeding 80 bar, designed for treating high-salinity brines and achieving maximum water recovery. HPRO is used in zero-liquid discharge (ZLD) systems, mining wastewater treatment, and concentrate management. Tech Inc. high-pressure test cells are engineered to withstand these demanding operating conditions.

What is Loose Nanofiltration?

A subcategory of nanofiltration membranes that exhibit higher permeability and lower rejection than tight NF membranes. Loose NF is used for selective removal of organic micropollutants while allowing monovalent salts to pass through, making it useful in pharmaceutical separations and dye removal from textile wastewater.