Magnesium chloride is commonly used as a coagulant and disinfectant in water treatment. It can help remove suspended matter and harmful substances from the water, while also killing bacteria and viruses in the water. In sewage treatment, magnesium chloride can promote sludge settlement and separation, thereby improving water quality. In addition, magnesium chloride can also be used in the desalination process to produce fresh water by removing salt from seawater. In short, magnesium chloride plays an important role in water treatment, helping to improve water quality and protect the environment.