Membrane clogging in ultrafiltration water purification equipment directly impacts its filtration efficiency and lifespan. Effective prevention requires a comprehensive approach encompassing water quality control, pretreatment optimization, operational parameter adjustment, cleaning and maintenance, membrane module selection, and operational procedures.
Water quality control is fundamental to preventing membrane clogging. Raw water containing high levels of suspended solids, organic matter, microorganisms, or colloidal particles accelerates the formation of deposits on the membrane surface. For example, oily substances in industrial wastewater and algae and colloidal silica in surface water easily form an adhesion layer on the membrane surface, leading to a decrease in flux. Therefore, key indicators must be controlled specifically based on the characteristics of the influent water: for high-turbidity sources, the suspended solids content must be reduced; for wastewater containing organic matter, COD (Chemical Oxygen Demand) and BOD (Biochemical Oxygen Demand) must be reduced; for water sources with a high risk of microbial contamination, bacterial growth must be inhibited. Source control can significantly reduce the membrane fouling load.
Optimization of the pretreatment process is a crucial line of defense. Conventional pretreatment includes multi-media filtration, activated carbon adsorption, and security filtration, which can intercept large particulate impurities and some colloids. For specific pollutants, enhanced pretreatment methods are necessary: if the raw water contains iron and manganese ions, aeration oxidation and manganese sand filtration devices should be added to prevent the deposition of iron and manganese oxides; if colloidal fouling is severe, flocculants (such as polyaluminum chloride) can be added to promote colloid coagulation, followed by removal through sedimentation or filtration; for oily wastewater, air flotation or oil-water separators are required for oil-water separation. Through staged pretreatment, the concentration of pollutants entering the ultrafiltration system can be significantly reduced.
Precise adjustment of operating parameters directly affects the membrane fiber's resistance to fouling. Transmembrane pressure differential (TMP) is a key indicator and must be controlled within a reasonable range: too low a TMP will lead to insufficient filtration drive and reduced permeate flow; too high a TMP may exacerbate deposition on the membrane fiber surface and even cause irreversible fouling. Therefore, the operating pressure needs to be dynamically adjusted according to the influent water quality and the design parameters of the ultrafiltration water purification equipment. Furthermore, flow rate optimization is crucial: increasing the feed water velocity enhances membrane surface shear and reduces contaminant deposition, but excessively high velocities may increase energy consumption; while reducing the velocity saves energy, it can exacerbate concentration polarization. The optimal flow rate range needs to be determined experimentally to achieve a balance between efficiency and energy consumption.
Regular cleaning and maintenance of ultrafiltration water purification equipment is essential for restoring membrane performance. Cleaning methods include physical and chemical cleaning: physical cleaning removes loose deposits from the membrane surface through reverse water flow or air scrubbing; chemical cleaning uses agents targeted at specific contaminants, such as acidic cleaning agents to dissolve inorganic scale (e.g., calcium carbonate, calcium sulfate), alkaline cleaning agents to decompose organic matter and biological slime, and oxidizing cleaning agents (e.g., sodium hypochlorite) to kill microorganisms. The cleaning cycle needs to be determined based on water quality and operating conditions: for water sources with high pollution risk, the cleaning interval should be shortened; for scenarios with stable water quality, the cleaning cycle can be extended. In addition, over-cleaning should be avoided to prevent damage to the membrane fibers; for example, excessively high concentrations of alkaline cleaning agents may damage the membrane material structure.
The selection and installation quality of membrane modules directly affect their anti-fouling performance. Hollow fiber membranes, due to their large specific surface area and high filtration efficiency, are the mainstream choice, but they have high requirements for influent water quality. Tubular membranes, while having strong anti-fouling capabilities, consume more energy. A balance must be struck based on actual needs when selecting a model. During installation, it is crucial to ensure the verticality and sealing of the membrane modules to avoid uneven flow rates caused by installation deviations, which can lead to fouling hotspots. Furthermore, the precision of the membrane module cutting machine also affects the integrity of the membrane fibers: high-precision cutting reduces fiber breakage and lowers the risk of localized fouling caused by broken fibers.
Strict adherence to operating procedures is essential for preventing clogging. Operators must receive professional training and be familiar with the equipment startup, operation, shutdown, and cleaning procedures. For example, a low-pressure flush is required before startup to remove air from the system; during operation, TMP, permeate flow, and water quality indicators must be monitored in real time to promptly detect any abnormalities; a protective flush is required upon shutdown to prevent membrane fiber drying and shrinkage, which could cause structural damage. In addition, a comprehensive maintenance record must be established, documenting cleaning cycles, chemical dosages, and performance changes to provide a basis for optimizing operating strategies.
