Various methods are used to purify consumer water and industrial water. The most common and easiest way is to install filters. But filters often get clogged and when cleaning water containing very small impurities, they do not always cope with their task. But fortunately, much more effective methods have been invented for water purification, one of which is the use of coagulant substances.
Coagulants are substances that can react chemically with pollutants in water. The most popular for water purification are now aluminum hydroxochlorides, which contain aluminum oxide , aluminum, iron and other components. Initially, ordinary food salt NaCl was used as a coagulant, but since chlorine is a monovalent metal and aluminum is trivalent, its use is almost 1000 times more efficient.
Molecules of coagulants have a positive charge, while impurities have a negative charge of molecules. The latter fact suggests that the particles of impurities do not combine with each other and, when shaken, make the water cloudy. In such a "suspended" state of impurity particles, it is very problematic to remove them using filters. Accordingly, pathogens continue to be present in the water and it is impossible to consider water fit for human consumption.
Due to the positive charge of the molecules, coagulants stably bind the particles of impurities, from which a white precipitate is ultimately formed, and the water becomes transparent. One molecule of active substance can attract several molecules of a pollutant at once. But this number is limited, so it is necessary to calculate the required amount of coagulants for a certain volume of water and take into account the degree of its pollution. Now a fairly coarse filter will work to remove the formed sediment, since it is quite coarse.
