During long-term operation, hollow fiber ultrafiltration membranes are affected by feed properties, operating conditions, and environmental factors. Contaminants gradually accumulate on the membrane surface, leading to decreased flux and reduced separation efficiency. Therefore, establishing a scientifically sound maintenance cycle is a core management measure to ensure the continuous and efficient operation of the membrane system.
Determining the maintenance cycle requires comprehensive consideration of factors such as feed water quality, operating flux, operating pressure, and water temperature. Generally, under conditions of relatively stable water quality, adequate pretreatment, and moderate operating load, chemical cleaning can be performed every 3 to 6 months. If the feed water has high turbidity, high oil or organic matter concentration, and an accelerated fouling rate, the cycle should be shortened to 1 to 3 months, supplemented by online physical backwashing or air wiping as routine maintenance. For continuously operating systems, short-term physical cleaning is recommended weekly or bi-weekly to slow contaminant accumulation.
Routine maintenance includes monitoring changes in transmembrane pressure differential, permeate flow fluctuations, and influent and effluent water quality indicators. If a significant increase in transmembrane pressure differential or a flux decrease exceeding 15% of the baseline value is detected, a targeted cleaning procedure should be initiated. Chemical cleaning typically employs a phased strategy: first, alkaline agents remove organic and biological fouling, followed by acidic agents to remove inorganic salt scale. Dispersants may be used when necessary to enhance cleaning effectiveness. Thorough rinsing is essential after each cleaning to prevent chemical residue from damaging the membrane material.
Furthermore, maintenance cycles are not fixed and should be adjusted according to seasonal changes and the source of the raw water. For example, significant differences in water quality during rainy or dry seasons necessitate more frequent monitoring and dynamic adjustments to the cleaning plan. During long-term shutdowns, thorough cleaning, sterilization, and moisture retention should be performed according to established procedures to prevent microbial growth and membrane performance degradation.
Scientifically developing and strictly adhering to maintenance cycles not only extends membrane lifespan but also maintains the economic efficiency and stability of the system, providing a solid guarantee for the reliable application of hollow fiber ultrafiltration membranes in various fields.
