The water quality standards used in agricultural irrigation are different from those for drinking water. Generally speaking, agricultural irrigation water does not need to meet the high standards of drinking water, but it must meet the growth needs of crops and cannot cause adverse effects on soil and plants.

The main types of water treatment plants are: 1. Drinking water treatment plants, 2. Sewage treatment plants, 3. Industrial water treatment plants, 4. Seawater desalination plants.