Differential Pressure (∆P) alone should not be used as an indicator of membrane scaling/fouling. Increases in differential pressure (∆P) across a stage indicate that a foulant has growth thick enough to interfere with flow through the feed channels. However, not all foulants/scales form the thick deposits needed to obstruct the channel; many form a consistent membrane coating that reduces productivity without significantly impacting ∆P. A typical scale only gets thick enough to cause an increase in ∆P when it has become very severe, making membrane cleaning much more challenging. Some scales such as calcium sulfate even become completely irreversible if allowed to reach a certain thickness.
Always base your membrane cleaning on decreases in Normalized Permeate Flow.
