“Water treatment chemicals (also known as water treatment agents) are chemical substances commonly required during the processing of industrial water, domestic water, and wastewater.”
Their primary functions include controlling the formation of scale and sludge, reducing corrosion in materials that come into contact with water, removing suspended solids and toxic substances, deodorizing and decolorizing, and softening and stabilizing water quality. These chemicals are widely used across various sectors—including the chemical, petroleum, light industry, personal care, textile, printing and dyeing, construction, metallurgy, machinery, healthcare, transportation, and environmental protection industries—supporting processes such as wastewater and sewage treatment, cooling and boiler water treatment, seawater and brackish water desalination, membrane separation, biological treatment, flocculation, and ion exchange.
1. Polyacrylamide (PAM)
Polyacrylamide is a linear polymer. The key difference between PAM and PAC (polyaluminum chloride) is that PAM is organic, whereas PAC is inorganic. At room temperature, PAM exists as a glassy solid that is soluble in water at any ratio, forming a transparent aqueous solution; it is typically used in flocculation processes. However, the practical application of PAM is complex. Once the optimal dosage is determined, the chemical must be added in batches and stirred continuously until fully dissolved before use.
2. Polyaluminum Chloride (PAC)
Polyaluminum chloride (PAC) is a water-soluble inorganic polymer with properties intermediate between AlCl₃ and Al(OH)₃. It exhibits strong bridging and adsorption capabilities. During hydrolysis, it facilitates physicochemical processes such as coagulation, adsorption, and precipitation, and is commonly used in coagulation applications.
PAC comes in various colors, including white, pale yellow, golden yellow, brown, tan, and coffee-brown. The color depends on the raw materials and production processes used; white PAC offers the highest purity and commands the highest price. Pale yellow PAC is considered a premium grade and is frequently used for drinking water treatment; golden yellow PAC is widely used and moderately priced; while other varieties are utilized in industrial or specialized applications. 3. Caustic Soda Flakes
Caustic soda flakes, also known as sodium hydroxide, are an inorganic compound primarily used to adjust pH levels; they are highly alkaline, whereas typical wastewater tends to be acidic. They are mainly used in dissolved air flotation (DAF) tanks or equalization tanks, where maintaining an appropriate pH helps prevent sludge from floating to the surface. Additionally, caustic soda flakes can facilitate the removal of heavy metal ions through precipitation. They are a common chemical agent in wastewater treatment.
4. Biological Agents
Biological agents refer to live bacterial preparations made by cultivating target microorganisms (beneficial bacteria) via industrial processes and adsorbing the resulting bacterial fermentation broth onto porous materials (such as peat or vermiculite). They typically come in liquid, powder, or granular forms. In wastewater treatment, they are used to replenish the microbial populations required for biological treatment processes.
5. Carbon Sources
Nutrients containing carbon that can be utilized by microorganisms for growth and reproduction are collectively known as carbon sources. Common examples include sugars, oils, and organic acids. Carbon sources serve as food for microorganisms, providing them with energy and the carbon framework needed to synthesize cellular components and products.
6. Citric Acid
Citric acid is an important organic acid. It appears as colorless, odorless crystals with a strong sour taste and is highly soluble in water. It is primarily used for the backwashing of MBR (Membrane Bioreactor) systems, where it dissolves salt-based deposits and fouling on the membrane surface.
7. Sodium Hypochlorite
Sodium hypochlorite is an inorganic compound used in a wide range of fields, including bleaching, industrial wastewater treatment, textiles, and manufacturing. In water treatment, it serves as a water purification agent, bactericide, and disinfectant, and is also used for backwashing to remove organic fouling from MBR membranes.
Application Areas
Depending on the specific water treatment targets and methods of the end-users, the application areas for water treatment chemicals can generally be categorized as follows: industrial water treatment, municipal and drinking water treatment, sewage and wastewater treatment, and seawater desalination.
In the industrial sector, water treatment chemicals are primarily used in circulating cooling water systems and industrial boiler water. Circulating cooling water involves cooling used water via a cooling tower for reuse; the entire system operates in a continuous, dynamic cycle, allowing for multiple uses. These systems require solutions to address issues such as scaling, corrosion, and microbial growth within pipelines and equipment. Key chemicals used in industrial circulating water treatment include scale inhibitors, corrosion inhibitors, biocides/algaecides, cleaning agents, and film-forming agents.
Common methods for industrial boiler water treatment include external and internal treatment; chemicals employed include corrosion and scale inhibitors, oxygen scavengers, feedwater alkalinity reducers, ion exchangers, regenerants, softeners, alkalinity adjusters, and descaling agents. In the production of potable water, municipal treatment facilities must add appropriate chemicals to ensure the finished water meets national standards. Key treatment stages include: algae control (reducing toxic or odor-causing algae in reservoirs); flocculation (removing suspended and colloidal solids like clay); softening (removing calcium and magnesium salts, particularly carbonates and bicarbonates); corrosion control (minimizing pipeline corrosion); and disinfection.
Chemicals commonly used in municipal and drinking water treatment include biocides/algaecides, flocculants, and corrosion inhibitors. Regarding sewage and wastewater treatment, direct discharge into the natural environment would cause pollution; therefore, all contaminants must be removed. This process typically combines multiple treatment methods to achieve multi-stage purification and filtration until contaminants are completely eliminated.
Chemicals involved in sewage treatment include flocculants, sludge dewatering agents, defoamers, chelating agents, and decolorizing agents. Seawater desalination technology emerged in the 1960s and has matured significantly over the ensuing decades; distillation and membrane-based processes have become the dominant technologies. In membrane-based processes, chemicals such as slow-release scale inhibitors, cleaning agents, flocculants, and scale-inhibiting dispersants must be added to the water to mitigate the impact of scale deposition on reverse osmosis membranes. In distillation processes, scale formation tends to reduce evaporation efficiency; this impact can be minimized through seawater pretreatment and the addition of agents—such as polyphosphates, organic phosphonic acids, and phosphono-polycarboxylic acids—to the feedwater. These agents soften the water by chelating calcium, magnesium, and other metal ions, thereby preventing them from precipitating and forming scale.
Future Prospects and Opportunities
Development Outlook
Demand for Energy Conservation and Emission Reduction: My country has a vast territory and a large population, yet its per capita freshwater resources are low, and water reuse rates remain relatively modest. Rapid economic growth in recent years has led to increased water consumption in both industrial production and daily life, while pollution issues have continued to intensify. Water treatment chemicals have proven highly effective in the treatment of industrial cooling water. Furthermore, their application in municipal sewage treatment plays a significant supporting role, which is crucial for improving water utilization efficiency and alleviating water scarcity.
Stricter Environmental Standards: To manage and improve water quality across my country’s river basins, the government has introduced various policies and progressively raised sewage discharge standards. This has provided a clear direction for the R&D of novel water treatment chemicals and created excellent opportunities for industry growth.
Demand for Water Environment Improvement: Currently, phosphorus-based products dominate the market for scale inhibitors in my country’s industrial sector, with annual consumption reaching approximately 100,000 tons. Most of these phosphorus-containing compounds eventually enter natural water bodies, causing eutrophication in rivers and lakes and posing a serious threat to the ecological environment. Consequently, the research and promotion of non-toxic, phosphorus-free, and biodegradable water treatment chemicals have become critically important. Technical System Support: My country is currently transitioning its water environment management from a model based on total quantity control to one focused on target-based management for specific river basins. The state is vigorously promoting the construction of technical and integrated management systems for water pollution control; this provides robust technical backing for the development of water treatment chemicals and creates a broader platform for their advancement.
Development Opportunities:
Innovation is the driving force behind the sustainable development of water treatment chemicals, and “greening” represents the future direction of the industry. Developing green water treatment chemicals that meet my country’s environmental protection standards—characterized by low phosphorus content, nitrogen-free composition, biodegradability, non-toxicity, and low cost—will be the key focus for future development. Regarding organic polymer flocculants and multi-component composite flocculants, recent research into mechanisms such as adsorption-bridging, charge neutralization, and depletion flocculation (involving polymer-particle surface complexes)—as well as studies on polyelectrolyte complexation and enhanced flocculation of refractory organics via micellar adsorption—has provided a theoretical foundation for their development and application. Consequently, a range of new, high-efficiency, and eco-friendly organic polymer and multi-component composite flocculants have been developed, marking a significant breakthrough in the field. The evolution of green water treatment chemicals has progressed from natural polymer-based agents to synthetically produced polymer agents. Developing new green agents that offer high scale-inhibition performance and good biodegradability, while being non-toxic and phosphorus-free (or low-phosphorus), is the direction for the 21st century. However, while scale inhibitors and corrosion inhibitors have made some strides toward becoming “green,” flocculants—which are the most widely used water treatment chemicals—still present issues; currently utilized inorganic and organic flocculants can cause secondary pollution and pose significant risks to human health. Therefore, research and development efforts to make flocculants more environmentally friendly must be intensified. During development, natural products—such as those from agriculture and forestry—serve as raw materials. Combined with water-in-water (W/W) emulsion polymerization technology, this approach ensures environmentally friendly production and usage while eliminating secondary pollution.
Multi-component composite water treatment agents offer multiple functions within a single product. For instance, polysilicic acid-aluminum salt composite flocculants—a type of novel inorganic polymer coagulant—are derived from activated silicic acid (polysilicic acid) and aluminum salt coagulants. They function through both charge neutralization and adsorption-bridging mechanisms, offering advantages such as superior coagulation performance, low cost, and minimal residual aluminum in treated water. Another example is the poly-haloalcohol-thiolin quaternary ammonium salt flocculant; characterized by strong flocculation capabilities, it is particularly suitable for separating ore from water in mineral processing operations and also provides certain bactericidal and sustained-release effects. The multifunctional nature of these composite agents has attracted increasing research interest regarding their preparation processes and practical applications.
Novel, high-efficiency water treatment agents such as nanomaterials and microbial flocculants
(1) Nanomaterials—exhibiting properties such as small-size effects, surface effects, quantum size effects, and macroscopic quantum tunneling effects—hold great promise as novel, high-efficiency water treatment agents. Breakthroughs have already been achieved in areas such as the photocatalytic degradation of toxic organic pollutants using nano-TiO₂ and the removal of heavy metals using modified carbon nanotubes, paving the way for the further development of nanomaterial-based water treatment agents.
(2) Microbial flocculants are non-toxic biopolymer compounds—comprising functional proteins or polysaccharides—that possess unique biodegradable properties. Compared to other flocculants, microbial flocculants offer numerous advantages, including ease of solid-liquid separation, minimal sludge formation, biodegradability, non-toxicity, and high practical utility. Currently, there is extensive research on microbial flocculants, and some researchers have achieved excellent results by using inorganic-organic polymer flocculants in combination.