Water treatment chemicals are diverse and can be broadly categorized based on their functional characteristics. First, there are flocculants and coagulants. These chemicals cause tiny suspended particles and colloidal substances in water to aggregate, forming larger flocs, thus accelerating sedimentation or flotation and achieving solid-liquid separation. Common flocculants include polyaluminum chloride, aluminum sulfate, and polyferric sulfate, which are widely used in water treatment and effectively remove suspended solids, organic matter, and some heavy metal ions. For example, when treating domestic sewage, polyaluminum chloride is typically added at a dosage of 10-50 mg/L, which can significantly reduce the turbidity of the sewage and significantly improve the quality of the effluent. Second, there are disinfectants, used to kill bacteria, viruses, and other microorganisms in water, ensuring water safety. Common disinfectants include chlorine, chlorine dioxide, ozone, and sodium hypochlorite.
Chlorine is a traditional disinfectant with a relatively low price, but it produces some disinfection byproducts during use, posing certain potential risks to human health. Chlorine dioxide has strong oxidizing properties, excellent disinfection effect, and does not produce carcinogenic halogenated hydrocarbons, leading to its increasingly widespread use in recent years. Ozone disinfection offers advantages such as high efficiency, speed, and no residue, but its equipment investment and operating costs are higher. Next are scale inhibitors and corrosion inhibitors. In industrial circulating water treatment, calcium and magnesium ions in the water easily form scale, which adheres to equipment surfaces, affecting heat transfer efficiency and service life, and also corroding metal equipment. Scale inhibitors prevent scale formation, while corrosion inhibitors slow down the corrosion rate of metal equipment. Common scale inhibitors include organophosphates and polycarboxylic acids, while corrosion inhibitors include chromates and zinc salts (although chromates are gradually being used less due to their high toxicity).
In addition, there are pH adjusters to regulate the acidity or alkalinity of the water to a suitable treatment range; and reducing agents to remove oxidizing substances from the water. When selecting water treatment chemicals, it is necessary to comprehensively consider factors such as water quality characteristics, treatment process requirements, cost, and environmental protection requirements. For example, for water with high hardness, highly efficient scale inhibitors should be selected; for drinking water with strict requirements on microbiological indicators, safe and reliable disinfectants should be chosen. Meanwhile, with increasingly stringent environmental protection requirements, green, environmentally friendly, and efficient water treatment chemicals will become the future development trend.
