Micro filtration and ultra filtration
| The principle of micro filtration and ultra filtration is physical separation. The extent to which dissolved solids, turbidity and microrganisms are removed is determined by the size of the pores in the membranes. Substances that are larger than the pores in the membranes are fully removed. Substances that are smaller than the pores of the membranes are partially removed, depending on the construction of a refuse layer on the membrane. |
Micro filtration and ultra filtration are pressure-dependent processes, which remove dissolved solids and other substances from water to a lesser extend than nano filtration and Reverse Osmosis.
Membranes with a pore size of 0.1 – 10 µm perform micro filtration. Microfiltration membranes remove all bacteria. Only part of the viral contamination is caught up in the process, even though viruses are smaller than the pores of a micro filtration membrane. This is because viruses can attach themselves to bacterial biofilm.
For complete removal of viruses, ultra filtration is required. The pores of ultra filtration membranes can remove particles of 0.001 – 0.1 µm from fluids.
Protection of membranes
Ultra filtration can also be applied for pre-treatment of water for nano filtration or Reverse Osmosis.
When wastewater is treated it needs to answer certain demands. It depends on these demands whether or not permeates need additional treatment after microfiltration or ultrafiltration.