Reverse osmosis plants
are quite exclusively constructed by installing spiral wound membranes.
They work with medium- high pressure depending on the type of
application (6 - 80 bar) and they are applied to separate the dissolved
salts from aqueous solutions by means of semi-permeable membranes. In
this case the dimension of membrane pores are very small so that the
resistance to the passage of water is higher.
The technology and process involved are relatively simple, membranes
representing very fine filters, which act like sieves through which
water is either pressed or sucked. Any content, which is larger than the
microscopic pores, is separated out and depending on the ineness of the
filter, a differentiation is made between
micro filtration,
ultra filtration, and
nano filtration.
Reverse osmosis is an additional variation, in which only water molecules pass through the membrane.