What is the Difference Between Reverse Osmosis and Nanofiltration, Ultrafiltration and Microfiltration?

To understand the difference between industrial reverse osmosis and industrial filtration based ultrapure water processes (nanofiltration, ultrafiltration, and microfiltration) lies in an understanding of total dissolved solids (TDS) and total suspended solids (TSS). There are some substances that can be removed from water by an ultrafiltration method. These removable substances are considered total suspended solids (TSS) as they are suspended particles in the water. Total dissolved solids (TDS) are the remaining substances that pass through the filter.

Total suspended solids (TSS) are measured by the clarity of water and presence of suspended particles, referred to as turbidity (NTU). Total dissolved solids (TDS) are measured by their conductivity.

Ultrafiltration processes (microfiltration, ultrafiltration) use pressure to separate high-molecular weight substances, suspended solids, bacteria, protozoa and some viruses from water. These substances include small unseen particles, like viruses, all the way to small particles that can be seen, such as sand. The reverse osmosis and nanofiltration takes the purification process further by targeting what the other ultrapure filtration methods cannot, maily dissolved solids. The chart below shows examples of the types of particles that can be removed by the various filtration approaches.

The levels of filtration are as follows, going from the most robust to least robust at removing small particles. As a general guide, industrial filtration and industrial reverse osmosis particle removal can divided roughly by an order of magnitude:

  • Microfiltration (~0.1 micron)
  • Ultrafiltration (~0.01 micron)
  • Nanofiltration (~0.001 micron)
  • Reverse osmosis (~.0001 micron)

Chart of Particle Sizes and Filtration Spectrum

Which is the best level of filtration for your industrial water or lab water application? In absolute terms, industrial reverse osmosis will remove the smallest particles and ions among these options. However, what is best for your industrial water or lab water system will depend on your water requirements. If ultrafiltration is suitable for your needs, it may provide the best combination of cost, efficacy and effectiveness for your water filtration needs.

Note that both reverse osmosis and ultrafiltration systems can be used together or configured with various pre- and post-treatment equipment to achieve your ideal process, depending on water conditions and quality requirements. Industrial Water Solutions customizes our solutions to every client and can work with you to deliver cost effective and efficient ultrapure water treatment. Contact us today.