Compaction

Compaction is defined as the deformation of the membrane and membrane backing material under pressure.  There are two possible consequences to compaction: One is the embossing of the membrane backing into the permeate spacer material. This results in increased pressure losses on the permeate side of the element, thus reducing flow, or conversely, requiring higher pressures to maintain specified flows. The second potential consequence is the compression of the porous polysulfone membrane support material, which is sandwiched between the rejecting membrane layer and the polyester backing.  Compression of this layer also reduces flow. However, significant compression of the polysulfone layer generally occurs only at very high pressures.

A certain amount of membrane compaction is inevitable due to construction from plastics and textile materials that all deform under pressure. Only when compaction becomes severe is element performance significantly compromised.

Symptoms of compaction include:

• Loss in permeate flow