How can you determine whether the membranes in your RO system are damaged?

There are various symptoms that can indicate membrane damage; however, an accurate diagnosis requires a systematic evaluation, starting with data normalization and often concluding with a membrane autopsy. At AWC®, we emphasize that operating a system with damaged membranes doesn’t just compromise water quality, it leads to increased operational costs, reduced membrane life, and irreversible damage to your system.

Here are several common indicators of membrane damage:

Loss in permeability that doesn’t recover even after aggressive cleaning: This is usually a sign of irreversible damage.  It can occur as a result of membrane dehydration, exposure to certain solvents that cause pore collapse, cationic polymers or surfactants that irreversibly bind to the membrane, or oxidation by halogens like iodine, which impact permeability through steric effects. More recently, AWC has identified situations where the use of chloramines in water reuse RO applications caused irreversible losses in permeability when the feed water pH was below 6.5.

Dramatic increase in permeability coupled with an increase in conductivity: This is usually a sign of halogenation by chlorine or oxidation by permanganate or chlorine dioxide. While some oxidizers, such as peroxide and peracetic acid, are generally considered membrane-compatible at reasonable concentrations, the presence of transition metal particles (such as Iron, manganese, and cobalt) will catalyze the formation of free radicals, resulting in very extreme localized damage. Severe delamination would also exhibit similar symptoms. Membrane probing can determine whether an increase in permeate conductivity is simply due to leakage at the permeate tube interconnectors (damaged O-ring). Still, such leakage would not exhibit a severe increase in permeability.

Increase in differential pressure (ΔP) in combination with increased conductivity: Continuing to operate a system while experiencing high differential pressure will cause telescoping and/or feed spacer migration. The movement of the membrane media will result in membrane abrasion and an irreversible loss in permeate quality. This will be exacerbated by any deposits that were trapped at the feed spacer contact points.

Increase in conductivity with no significant increase in permeability: This is usually due to minor delamination caused by a leaking check valve or as a result of CIP performed with the permeate valve closed.  Other causes can be due to suspended solids abrasion or inadequate scale control, resulting in the growth of sharp crystals that tear into the active membrane layer.

Consequences of Poor Salt Rejection

When RO membranes are damaged or degraded, one of the most critical outcomes is poor salt rejection. This can lead to serious issues across a range of applications. These include microbial contamination, inadequate removal of harmful contaminants such as arsenic, nitrate, boron, or PFAS, increased ion exchange resin loading, degradation of product water quality, and losses in energy efficiency or overall system performance. Poor salt rejection poses a risk to safety, compliance, cost, and operational reliability. That’s why proactive membrane monitoring and timely autopsies are essential.

Why a Membrane Autopsy Matters

Completing a membrane autopsy is the most definitive method for confirming and understanding the extent and root causes of membrane damage. At AWC, we perform up to 25 analytical tests to uncover what can’t be seen in system performance data alone. Without proper diagnosis, operators risk continuing with ineffective cleanings, inaccurate chemical dosing, or prematurely replacing membranes, which can result in wasted time, money, and water.

Don’t Operate Blind

Operating an RO system with compromised membranes can significantly reduce recovery, increase energy consumption, and necessitate frequent cleanings or even system failure. If you notice signs of membrane degradation, contact AWC. Our trusted membrane experts will guide you through the right steps, from water analysis to autopsy, so you can make informed decisions, protect your assets, and restore optimal performance.