The spiral wound element type is the workhorse in the membrane world.
The spiral wound element design was originally made exclusively for water
desalination, but the very compact design and the low price made it
attractive to other industries. After a lot of trial and failure, redesigned
elements emerged which can be used for a variety of industrial applications
in the dairy industry, the pulp and paper industry, for high purity water, and
at high temperature and extreme pH, but the number of membrane
companies who really can and will develop and supply spiral wound elements
for extreme applications is in many cases limited to one.