How much oxygen is in water

Oxygen content of the water

The oxygen content of the water is the result of processes that supply and consume oxygen. Oxygen is brought in from the atmosphere, whereby the oxygen uptake mainly depends on the size of the water surface, the water temperature, the saturation deficit, the water turbulence and the air movement. Oxygen is also released during photosynthesis in aquatic plants. This can lead to oxygen oversaturation. On the other hand, during the natural breakdown of organic substances in water, oxygen is consumed by the activity of microorganisms and by the respiration of animals and plants. This can lead to a lack of oxygen in the water. The "fish critical value" is an oxygen content of 3 mg / l, below which fish can be harmed.

Due to the dependence of the oxygen concentration on the various physical, chemical and biochemical factors and the resulting great variability (including day-night rhythm in eutrophic waters), the dynamics of the oxygen balance in the water can usually only be recorded by continuous measurement and registration .

The measurement of dissolved oxygen is widely used in water monitoring and wastewater engineering. Oxygen is an essential component for the aerobic metabolic processes in every body of water. Water pollution often leads to "oxygen depletion" as a result of the biological degradation of the organic matter. Accordingly, the oxygen content of a natural body of water is a criterion for assessing the ecological situation and, in wastewater technology, a measurement variable for regulating the treatment plants.