The operation methods of hollow fiber ultrafiltration membranes directly affect the separation effect, membrane life, and system operating economy. Standardized procedures not only fully leverage their high flux and high precision advantages but also effectively delay fouling and reduce maintenance costs.
A comprehensive inspection should be completed before startup. Confirm that the membrane module is securely installed, piping connections are correct, the pretreatment unit is operating stably, and the feed water quality meets the membrane's permissible range. In particular, turbidity, residual chlorine, and pH should be tested to prevent excessive substances from directly entering the membrane system. Check the opening and closing status of all valves to ensure that backwashing, blowdown, and venting circuits are unobstructed. For initial commissioning or restarting after a long period of shutdown, pre-flushing should be performed at low flow rate and low pressure, gradually increasing to rated operating conditions to avoid sudden impact damage to the fiber structure.
Key parameters must be closely monitored during operation. Transmembrane pressure differential reflects the degree of fouling, while permeate flow reflects the flux level; both should be consistent with design benchmarks. Generally, a stable cross-flow velocity should be maintained to enhance shearing and suppress concentration polarization. Pressure settings should not be kept close to or exceed the membrane's maximum tolerance for extended periods to prevent fiber compaction or breakage. Fluctuations in influent temperature and flow rate should be adjusted promptly, and buffering or bypass measures should be implemented if necessary to ensure system stability.
Regular physical cleaning is essential to maintain membrane performance. Short-term cleaning can be done using backwashing or air scrubbing to remove loose surface deposits. When the pressure differential increases or the flux decreases significantly, a chemical cleaning procedure should be initiated. Cleaning should be performed using appropriate chemicals and concentrations based on the nature of the contaminants, typically in a stepwise manner, first alkaline and then acidic, with strict control over contact time and temperature. After cleaning, the membrane must be rinsed with sufficient pure water until neutral to prevent chemical residues from corroding the membrane material or affecting effluent quality.
Shutdown procedures are equally important. The influent should be stopped first, followed by thorough evacuation and rinsing. Antibacterial treatment should be performed if necessary. For long-term shutdown, the membrane should be stored in a moisturized environment according to regulations to prevent dehydration, aging, or microbial growth. The entire operation process should be carried out by trained personnel, and with the cooperation of operation records and analysis, the operation strategy should be continuously optimized in order to achieve efficient, safe and long-term operation of hollow fiber ultrafiltration membranes.
