How do you identify the cause of membrane damage?

Two numbers, three scenarios

The two most useful pieces of data for diagnosing a membrane system are the production flow rate and the permeate conductivity. Neither is sufficient alone; you have to look at how they change together.

The three patterns below speed up diagnosis in the field.

What the patterns tell you

Always compare the values against their own history; it is the trend that matters, not the absolute number.

• Flow falling, conductivity steady: biological fouling is suspected
• Flow falling, conductivity rising: particle/clay fouling or scale–silica precipitation
• Flow rising and conductivity rising: a mechanical problem or chlorine damage

Why is the third scenario the worst?

A rising flow looks like good news at first glance, but if conductivity is rising too it means the membrane is no longer retaining what it should. That usually points to physical deterioration of the membrane surface, or to a mechanical leak such as an O-ring or a seal.

Chlorine damage produces the same pattern and is irreversible. That is why making sure free chlorine has been removed ahead of the membrane matters more than cleaning.