This is a long-term client we’ve worked with for years, and we’ll focus on their NF membrane system today. The client is based in Fujian Province, and their system runs with a total of 24 nanofiltration membrane elements. When they reached out to us, their main complaint was a drastic drop in permeate water output.

We always put solving customers’ problems first, so our technical team kicked off with a remote video consultation right away. After going through all the details, we spotted several critical issues.

The water production capacity in April fully met their operational demands, but by mid-May, permeate volume plummeted sharply. Besides, the NF system sat idle for quite a long time without running to produce water. This stagnant state triggered massive microbial growth and severe membrane fouling across the whole system. We also asked the client to run lab tests on their NF feed water, and the test results are as follows:

The test data shows extremely high COD and ammonia nitrogen levels in the feed water, which greatly raises the risk of heavy fouling on nanofiltration membranes.

At this point, the root cause of the low permeate flow became pretty clear. The main culprits behind weak water output are microbial contamination and organic fouling on the NF membranes. The site team had already carried out chemical cleaning, yet the cleaning barely helped. Another obvious sign: when they shut off the 2nd stage permeate valve, the 1st stage produced almost zero water, which proves the 1st stage suffered the worst fouling.

Our final solution suggestion: Start with non-oxidizing biocide disinfection, then perform alkaline cleaning on the system.

You can circulate and soak the whole system with non-oxidizing biocide via the cleaning unit. We recommend a biocide concentration of 1000ppm. Prepare 1 cubic meter of cleaning solution and follow this procedure: circulate for 30 minutes, soak for 2 hours, then circulate another 30 minutes. After the non-oxidizing disinfection, microbial biofilms on the membrane surface will peel off completely, which makes the subsequent alkaline cleaning far more effective.

From this case, you can see a universal truth for all water treatment membrane systems — ultrafiltration, nanofiltration, reverse osmosis, no matter imported or domestic membrane brands, malfunctions are inevitable. The core difference lies in whether you have a mature troubleshooting system, which boils down to rich industry experience and reliable after-sales support.

Alright, that’s all for today’s sharing. We’ll dive into more cases next time! Feel free to drop by XBYMC to chat and exchange ideas. Banzhang is always here waiting for you!