There is a problem of excessive pressure difference at the inlet and outlet of the RO security filter – how to solve it?

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Our company’s process is for the treatment of refinery wastewater, using pre-treatment followed by A/O. Secondary sedimentation tank – high-density sedimentation tank – ozone – BAF biological filter – sand filter – UF-RO: this is the process used for treating saline water, with the treated water being reused afterward. The issue at present is that the inlet and outlet parameters of the UF unit are within acceptable limits; sodium hypochlorite is added before the UF unit’s inlet, while reducing agents and scale inhibitors are added at the mixer located before the RO high-pressure pump at the outlet side. There are online pH and ORP meters in use, with the ORP value generally kept around 100. All test results indicate that the water entering the RO unit is of satisfactory quality. However, the pressure drop across the security filter reaches 0.1 MPA after about 2 days, requiring frequent replacement of the filter elements. Due to the high frequency of replacements, we now reuse the filter elements after soaking them in solutions such as sodium hydroxide or citric acid for about half a day. I don’t know what the problem is now? I suspected that the ORP online meter was inaccurate, and there were yellow contaminants at the mixer where the RO inlet and outlet pipes met; it resembled the color of PFS polyferric sulfate or PAC