The nano filtration technique is mainly used for the removal of two valued ions and the larger mono valued ions such as heavy metals. This technique can be seen as a coarse RO (reversed osmosis) membrane.
Applications for NF systems are:
Typical membrane performance for NF membranes are 50% NaCl removed and 90% (or more) for CaSO4
There are two types of membranes:
The surfaces from the filter determine the capacity from the filter. Spiral membranes have l the biggest surface area in general and are therefore the most cheapest in use. The surface area from Tubular/ straw membranes is less in general.
The pre purifying of the feedingwater has a influence on the performance of the installation. The need of pre purifying depends on the feedingwater quality.
Installing pre cleaning has the following advantages:
besides pre cleaning, a chemical doses can be taken place to prevent scaling, precipitation on the surface from the membrane.
A membrane system consists of several basic compounds: