Membrane Construction

This is an outline of the components of a spiral wound reverse osmosis membrane and their functions:

Membrane

This material prevents salt passage while allowing water to permeate. The membrane is typically made from polyamide with a polysulphone support layer.

Permeate Carrier (Tricot)

Sandwiched between layers of membrane, this material carries permeate water to the permeate tube.

Permeate Tube

A perforated tube which collects permeate and, upon which, the membrane leaves are attached. The ends of the permeate connector are profiled to hold interconnectors. These allow permeate to travel from element to element, and finally to the take-off point on the pressure vessel.

Anti-telescoping Device (ATD)

This device is fitted over the feed and concentrate end of the membrane. It is designed to prevent the membrane from elongating ("telescoping") due to pressure differential from feed to concentrate. It also holds the brine seal.

Feed Spacer (Vexar)

Fitted between membrane leaves, the vexar forms a flow channel for the feed water to pass over. It is designed to generate turbulence, breaking down boundary layers close to the membrane and helping to reduce scaling and fouling potential.