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Membrane filtration

The following processes are grouped together under membrane filtration:

  • Microfiltration (MF)
  • Ultrafiltration (UF)
  • Nanofiltration (NF)
  • Reverse osmosis (RO)

Membrane filters are purely mechanical "fine sieves". These fine sieves consist of porous, artificially created films, so-called membranes, with precisely defined pore diameters. The separating layers are applied to so-called carrier material. Polymers or ceramics are used as carrier materials. Membrane filtration technologies are used for the widest variety of applications in the water treatment field, often in conjunction with classical processes.

Separation limits

Membrane function

The pore diameters define the membrane type and relate directly to the separation rates: All substances smaller than the pores can pass through the membrane, and larger substances are held back.
In the context of drinking water treatment, this unselective process is disadvantageous, as both undesired and desired minerals are partially or totally removed, in particular at nanofiltration and reverse osmosis.

Membrane design

The actual effective membrane layer is extremely thin and is located on the side facing the raw water.
The absolutely largest part of a membrane is the carrier material required for the physical design and strength. It is important that the pores of a membrane increase in size toward the pure water in order for the membrane to function properly. Otherwise, there is a risk of continuous blocking.

Membrane design
Basic structure of a membrane

Materials

Today’s membranes consist of plastics (e.g. polysulphone) or ceramic.

Types

A differentiation is made between the following, depending on the use and design:

  • Hollow-fibre membrane modules
  • Spiral modules
  • Pipe modules
  • Plate modules
  • Cushion modules

Method of operation

Membrane systems and any pre-processing require careful planning. The choice of the corresponding modules and the way in which the system operates must always be tailored to the raw water property.

Principle of a reverse osmosis system

We plan and build ultrafiltration systems, nanofiltration systems and reverse osmosis systems. To this purpose we avail ourselves of state-of-the-art knowledge and see great opportunities in the application of combination processes, such as ozone-supported membrane filtration.
Send us your requirements and we would be very happy to help you.

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