Ultrafiltration systems typically use hollow-fiber membranes, where raw water is pressurized either inside or outside the hollow-fiber modules, creating both external and internal pressure gradients. Ultrafiltration is a dynamic filtration process, allowing fouling substances to be removed via a concentrated stream without clogging the membrane surface. However, during ultrafiltration, accumulated contaminants on the membrane surface can lead to concentration polarization, which in turn reduces the membrane's permeability. By carefully selecting operational conditions and implementing effective cleaning protocols, ultrafiltration systems can effectively manage and mitigate the issue of concentration polarization.

　　At the initial stage of operation, the ultrafiltration equipment gradually integrates into the system until issues such as pressure rise, wastewater discharge, and reduced water production capacity occur. Over time, even with effective filters in use, factors like microbial and algal growth, electrostatic attraction between colloids and fiber aggregates, and organic fouling can lead to shorter operational cycles, diminished contaminant-retention efficiency, and an inability to detect significant pressure drops after water filtration ends. In such cases, chemical cleaning becomes necessary. The cleaning process involves soaking the filter overnight (24 hours) in a heated 3% NaOH and 0.55% NaClO mixture maintained at 30°C, followed by thorough steam-and-water rinsing. After completing the cleaning, the water reduction rate exceeds 98%, while the filter's contaminant interception capacity remains above 10 kg/m³.

　　Typical membrane flux for general products is designed at 25. The output of ultrafiltration equipment, however, depends on the operating temperature—since water viscosity changes with temperature, for every 1°C increase in temperature, the permeate flow rate increases by approximately 2%. Daily cleaning of the filter is performed using underwater suction combined with convective flushing, maintaining an air-inlet intensity around 60 L/(s·m³). This vigorous agitation thoroughly dislodges contaminants from the fiber bundle, ensuring complete removal of trapped particles.

　　Ultrafiltration equipment is mostly made from cellulose acetate or high-polymer materials with similar performance characteristics. It’s well-suited for separating and concentrating solutes in solutions and is also frequently used in other separation processes.

　　Ultrafiltration equipment technology excels in separating colloidal suspensions—tasks that are often challenging for other methods—and its applications continue to expand across various industries. Membrane filtration, driven by a pressure difference, is broadly categorized into three main types: ultrafiltration, microfiltration, and semi-permeable membrane filtration. These categories are distinguished based on the size of the smallest particles or the molecular weight range that the membrane can effectively retain. For instance, when using the membrane’s rated pore size as the distinguishing criterion, microfiltration (MF) membranes have a rated pore size ranging from 0.02 to 10 micrometers, while ultrafiltration (UF) membranes allow particles down to 0.001–0.02 micrometers. Reverse osmosis (RO) membranes, meanwhile, are designed to filter even smaller molecules, with a rated pore size of just 0.0001 to 0.001 micrometers.

　　Microfiltration membranes with consistent aperture specifications, featuring a rated pore size range of 0.001 to 0.02 m. This method employs ultrafiltration—a membrane filtration process driven by a pressure difference.

　　Ultrafiltration equipment can be manufactured in various forms, such as flat-sheet membranes, spiral-wound membranes, tubular membranes, or hollow-fiber membranes, and is widely used in fields like the pharmaceutical industry, food processing, environmental engineering, and more. As we know, a "membrane" functions like a sieve—it allows smaller particles to pass through while blocking larger ones. Ultrafiltration membranes are porous materials endowed with a "sieve-like" separation capability, featuring pore sizes ranging from just a few nanometers to tens of nanometers—roughly equivalent to 1/100th the width of a single human hair. By applying appropriate pressure to one side of the membrane, it becomes possible to selectively filter out solute molecules larger than the pore diameter, effectively separating particles with molecular weights exceeding 500 Daltons and sizes ranging from 2 to 20 nanometers.

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