With the rapid development of industry and agriculture in the world today, a large amount of industrial wastewater and farmland drainage is discharged into rivers, lakes and seas, and most of the domestic wastewater in small towns and rural areas is discharged in a disorderly manner, making the water quality in many places deteriorating and water pollution and water shortage increasingly serious, so there is an urgent need for timely monitoring and effective treatment of wastewater. Dissolved oxygen content in water is an important indicator when monitoring water quality.
Dissolved oxygen is oxygen dissolved in the molecular state of water, i.e. O2 in water, and is expressed as DO. Dissolved oxygen is indispensable for the survival of aquatic organisms. One source of DO is the infiltration of oxygen from the atmosphere into the water column when the water is not saturated with dissolved oxygen; another source is the oxygen released by plants in the water through photosynthesis. Dissolved oxygen varies with temperature, air pressure and salinity. Generally speaking, the higher the temperature, the greater the dissolved salinity and the lower the dissolved oxygen in the water; the higher the air pressure, the higher the dissolved oxygen in the water.
Dissolved oxygen in natural water is close to saturation (9ppm) and decreases when algal blooms are high. Water contaminated with organic and reducing substances can reduce dissolved oxygen. For aquaculture, dissolved oxygen in water has a vital impact on the survival of water organisms such as fish, and when it falls below 4mg/L, it can cause fish to suffocate and die.Breeders can use dissolved oxygen meters to monitor dissolved oxygen levels in the water and adjust water quality conditions in a timely manner.
For humans, the dissolved oxygen content in healthy drinking water should not be less than 6mg/L. When the dissolved oxygen (DO) consumption rate is greater than the rate of oxygen dissolved into the water, the content of dissolved oxygen can be close to 0, when the anaerobic bacteria can reproduce, so that the size of dissolved oxygen can reflect the pollution of the water body, especially the degree of organic pollution, it is an important indicator of the degree of pollution of the water body. It is also a comprehensive indicator of water quality.
The measurement of dissolved oxygen levels in water is therefore of great importance for environmental monitoring as well as for the development of aquaculture. Molecular oxygen in the air dissolved in water is called dissolved oxygen. The amount of dissolved oxygen in water is closely related to the partial pressure of oxygen in the air and the temperature of the water. Under natural conditions, the oxygen content in the air does not change much, so the water temperature is the main factor, the lower the water temperature, the higher the content of dissolved oxygen in the water.