Water in nature is not static, but constantly undergoes phase transitions and cyclical movements, known as the natural cycle of water. At the same time, in order to meet the needs of life and production, humans constantly extract water from natural water bodies, generating a large amount of domestic and production wastewater, which is discharged and reintroduced into natural water bodies. Water in nature contains various impurities, which can be divided into three categories based on their presence in water: suspended substances, dissolved substances, and colloidal substances. The types and quantities of impurities in natural water sources vary, and even within the same water source, the composition and content of impurities also change over time, location, and climate. When using reverse osmosis membranes to separate water and solutes, although the raw water is properly pretreated, impurities in the water will still accumulate on the surface of the membrane, causing membrane fouling, resulting in a decrease in membrane separation rate or permeability rate, or both. The types of membrane fouling usually include: insoluble salts in water scaling on the membrane surface, metal oxides and colloids, and microorganisms forming fouling. Membrane fouling is an inevitable phenomenon during membrane use.