The RO membrane, or reverse osmosis membrane, needs to be regularly cleaned and maintained to keep performing at peak efficiency. Without regular cleanings, a system can enter a fouled condition. If this condition is left unchecked or unaddressed for too long, it can hamper energy consumption and make it difficult to recover performance.
So, how often should RO membranes be cleaned? And what, exactly, does an RO membrane cleaning entail? From the regularity of cleaning to the treatment process, here’s what you need to know.
Regular Cleaning, Peak Performance
Most experts agree that an RO membrane needs to be cleaned when the flow rate has decreased by roughly 10% from accepted test conditions. A membrane cleaning should also take place if there’s an overall pressure drop of 15% over initial accepted test conditions. Unfortunately, many medical and industrial professionals don’t heed these explicit guidelines which can damage the membrane surface and lead to noticeable performance dips. As mentioned, if an RO clean is left unchecked for too long, it can even permanently damage the membrane surface which requires costly, time-intensive repairs.
Even still, with various clean-in-place (CIP) protocols and systems, problems can occur. Improper CIP use or the wrong cleaning solutions can exacerbate these problems greatly. When you’re cleaning a membrane, it’s important to analyze both your water and your system operations. By taking a look at these two specific features, you’re ruling out potential foulants and making it easier to determine what is impacting the membrane surface. It’s also a good idea to do this before you undergo a membrane cleaning so you can make the actual process run a bit more smoothly.
Inspecting a Membrane
Suppose you’ve noticed a pressure drop that falls below accepted test conditions. Before you request a cleaning, it’s a good idea to suss out any culprits. This can save you time, energy, and expenses for your future membrane cleaning. If the pressure drops in the first stage, it’s highly likely that it was caused by a colloidal from either organic or inorganic fouling throughout the system. However, this can also be indicative of bacterial fouling. Though bacterial fouling isn’t as common, it should still be taken very seriously as, unchecked, it could lead to costly repairs. For a colloidal issue, your RO system will benefit greatly from a low-pH soak and a subsequent alkaline cleaning.
If you’re experiencing final stage pressure drops, this is almost a surefire sign of mineral deposition. When this happens, your first action item should be to determine which kinds of minerals are fouling the system. By using a combination of mineral analysis, system projections, and antiscalant projections, it’s much easier to determine which types of minerals are more likely to deposit in your system than others. Depending on the type of scales, whether sulfate or carbonate, you’ll need either an alkaline chelant cleaner or a low-pH cleaner, respectively.
Many reverse osmosis systems come equipped with CIP protocols and systems. These allow you to handle membrane cleaning onsite without seeking outside assistance. However, for systems that aren’t CIP-enabled, or systems that have a faulty CIP or ongoing damages, it’s important to contact a provider for additional support. A provider with years of experience should be able to find and fit a CIP system that will work with your current industrial RO setup. On top of that, if there are necessary repairs, those added years of experience should make the maintenance process run that much more smoothly.
Ensure that you’re properly using the CIP on a regular basis and that you’re doing your utmost to keep your RO system free of contaminants, minerals, and other fouling substances. You’ll benefit from it in the long run.