Low‐pressure membranes: assessing integrity

Although low‐pressure membranes are effective for removing selected microorganisms from untreated water supplies, until now the monitoring of their integrity has been neglected. Several methods for monitoring the integrity of low‐pressure membranes were identified and evaluated using pilot‐scale systems. These techniques included particle counting, particle monitoring, turbidity monitoring, bubble‐point testing, air‐pressure‐hold testing, and sonic sensing. Although it does not provide continuous integrity monitoring throughout the filtration cycle, the air‐pressure‐hold test was the most effective direct monitoring method. Of the techniques that provide continuous monitoring, particle counting was the most sensitive.