Let's talk about dissolved oxygen (DO); it is the amount of gaseous oxygen that is dissolved in water, all aquatic life depends on the oxygen dissolved in water, the greatest amount of oxygen is obtained from the atmosphere, there are a variety of factors that influence the concentration of dissolved oxygen in water are: the atmospheric pressure, the content of salts in water and the temperature of the water.
To know the concentration of dissolved oxygen in the water two methods are commonly used: iodometric method and the technique of membrane electrodes; a high content of dissolved oxygen in the water is favorable in a water supply, since this means that the water is better, the levels of DO can vary from 0 - 18 parts per million (ppm), however, when the temperature rises decreases the amount of dissolved oxygen in the water.