xbymcHey guys, today let’s talk about how to tell real vs fake RO membranes!
We used to supply tons of Dow membranes years ago—they’re under DuPont now. We serve such a huge range of clients, so system malfunctions pop up every now and then. Large domestic power plants handle this fine; their teams run full diagnostics step by step, checking everything from pre-treatment all the way to the reverse osmosis membrane systems to pinpoint issues.
But small and mid-sized facilities are usually short-staffed. Whenever something goes wrong, their first thought is always: “Did you sell us counterfeit membranes?”
Let’s be real, the original Dow brand (now DuPont) is miles ahead when it comes to RO membrane quality control and industry reputation. That doesn’t mean trouble-free operation for users, though.
I’ll walk you through one of our client cases. This beverage manufacturer is based in Guangdong Province, China, and it’s pretty well-known nationwide. Back when we were an authorized direct project supplier for Dow, we completed dozens of projects for them. When their old RO membranes hit replacement time, they naturally came straight to us for new ones.
In January 2025, the client bought 18 pieces of BW30 PRO-400 membranes, all fitted into three pressure vessels in the second stage of their RO system.
In April the same year, they reached out with a problem: the newly installed 18 second-stage membrane elements produced poor-quality permeate water that failed their production standards.
Since they’re a long-term loyal customer, we sent our technical team to site right away to troubleshoot.
Timeline breakdown:
After the 18 BW30 PRO-400 membranes were installed in the second RO stage in Jan 2025, the conductivity reading for each pressure vessel sat around 5 μS/cm—well within their production requirements.
February 2025: The whole system shut down for roughly half a month. Once they restarted production, bacteria levels in the permeate spiked, yet water quality from the second-stage membranes stayed steady, conductivity still holding at ~5 μS/cm.
After detecting excessive bacteria, on-site operation staff performed two rounds of disinfection. When they fired the system back up afterward, the second-stage membrane water quality took a sharp turn for the worse.
April 2: The client tested permeate conductivity for every single membrane element inside three second-stage vessels (labeled #1, #4 and #7). You can see the test data in the chart below.
The figures made it clear: the last membrane element inside each vessel performed extremely poorly, dragging down the overall water quality of the whole pressure vessel. Conductivity per vessel jumped from the original ~5 μS/cm up to 13–14 μS/cm.
Since the faulty elements were all the last ones inside each of the three vessels, we rearranged all the membranes for testing. We moved the first four upstream elements from each vessel into two new vessels, and grouped the final two downstream elements from each vessel into a single separate vessel. We then retested permeate conductivity for every element—results are listed in the table below.
The post-rearrangement test results confirmed it: the six downstream elements that sat at the tail end of the original three vessels had the worst performance, with drastically reduced salt rejection. Their quality only deteriorated right after the system disinfection rounds. This proved the sanitizing chemicals caused permanent, irreversible damage to these membrane elements.
That’s where the root cause lies. The disinfection process ruined the membranes for good. If the permeate quality still meets production standards, they can keep running them; if not, they’ll need a full set of replacement membranes.
But the real story got way more complicated than we expected. I’ll fill you in on how we finally resolved this case next time!
