What reactions (actions) occurred in the process of water purification?

Physical purification: the dilution, diffusion, precipitation and volatilization of natural water reduce the concentration of pollutants.

1. chemical purification: redox, acid-base reaction, decomposition and coagulation of natural water change the existing form of pollutants and reduce the concentration.

2. Biological purification: the process of reducing the concentration of pollutants by biological activities in natural water. Especially important is the oxidative decomposition of organic matter by microorganisms in water.