## 1 Introduction  
Currently, desalination technology is mainly divided into thermal desalination and membrane desalination. The most widely used thermal treatment technologies are multi-stage flash distillation (MSF) and multi-effect distillation (MED), and the most widely used membrane treatment technology is RO. Compared with MSF and MED technology, RO has obvious advantages, such as the high quality of the produced water, small footprint, low operation cost, and convenient management [1; 2; 3; 4]. It is one of the most commonly used methods to solve the shortage of freshwater resources around the world [5; 6]. In 2018-2019, countries in the Middle East started to build large desalination projects [7]. As for China, it has been building an average of 10,000 m\({}^{3}\)/d of large-scale and small/medium projects per year since 2015, with RO dominating projects below 10,000 m\({}^{3}\)/d [8]. RO technology has accounted for more than half of the global desalination market since 2019 [9]. RO is not only used in large-scale desalination projects but also has many applications in brackish water, sewage, food processing, concentration, and separation [10; 11]. Although RO technology has reached a high level of maturity, there are still some challenges to overcome, mainly the problem of membrane pore clogging caused by the high salinity of the feedwater, pollutants, and so on, which in turn lead to a decrease in the osmotic flux of the membrane [1; 12; 13]. Membrane fouling can be categorized into organic, inorganic, biological, and colloidal fouling, which leads to the formation of salt crystals, cake layers, or biofilms on the membrane surface, resulting in increased transmembrane resistance and reduced permeate flux [14]. To understand the specific composition of fouling in RO, [PERSON] [15] dissected membranes operated during the winter season and found that organic and inorganic fouling exhibited a decreasing trend from the feed end to the permeate end; organic fouling was dominated by polysaccharides, proteins, and biological contaminants; and inorganic fouling was primarily composed of Al, Ca, Mg, Na, and K. It was also observed that organic fouling was more susceptible to microbial fouling. [PERSON] [16] proposed a scaling-based flux model to explain the scaling mechanisms in RO membranes: an increase in solute flux leads to supersaturation and scaling deposition; as the scaling layer thickens, the hydraulic resistance increases, reducing solute transport and decreasing supersaturation; when the scaling layer reaches a steady state, the hydraulic resistance stabilizes and the permeate flux through the membrane no longer decreases. [PERSON] [17] pointed out that mineral scaling is affected by the characteristics of the feedwater: different chemical properties in the feedwater lead to the formation of different types of mineral scaling, and the concentration polarization and concentration difference within the feedwater can both enhance the likelihood of scaling formation. Additionally, [PERSON] [18] discovered that ions can interact with each other, such as the interaction between calcium ions and alginate, forming a gel network that tends to aggregate near the membrane surface, creating a relatively dense fouling layer. [PERSON]'s [19] simulation study of the RO treatment of groundwater with minerals such as calcium and silica as the main constituents showed that relatively high flow recovery (R) could only be achieved with the addition of a scale antiscalant at the desired energy consumption, but higher R values (72%) required the addition of a special silica antiscalant, which was approximately twice as expensive as the normal scale inhibitor. [PERSON] [20] investigated the economics and energy consumption of RO desalination technology for brackish water and found that controlling the concentration of calcium, iron, and silicon in the feedwater is crucial to prevent scaling on the membrane surface, with calcium carbonate and iron scaling mitigated by adjusting the pH.