What is the dissolved oxygen coefficient?

The dissolved oxygen coefficient is expressed by KLa, KL represents the total mass transfer coefficient of liquid phase, and A represents the gas-liquid interface in each unit volume of fermentation broth; Because a is difficult to determine, KLa is often combined into a constant, indicating the rate of dissolved oxygen.

Dissolved oxygen refers to the dissolved amount of oxygen in water, which is one of the important indexes for aquatic organisms to survive in water. The content of dissolved oxygen varies with water temperature, atmospheric pressure and seawater salinity. Its dissolved oxygen in fresh water is slightly higher than that in seawater, usually 5 to 14 ppm.

Extended data:

First, the measurement method

One way to measure dissolved oxygen in water is to use titration (called Winkler titration), that is, Mn 2 is used to fix oxygen into a brown precipitate of Mn(OH)2, and then the amount of sodium thiosulfate is used to represent dissolved oxygen in water. Another rule is to measure the dissolved oxygen by the dissolved oxygen instrument method, that is, to measure the dissolved oxygen in water by the thin film electrode method.

Second, examples

According to the deployment of Fujian provincial government, Fujian Provincial Department of Ocean and Fisheries and Fujian Provincial Department of Environmental Protection organized a joint investigation team of experts and technicians to investigate the incident of cage culture of dead fish in Gutian section of Minjiang River from September 3 to 4, 20 1 1.

Through on-the-spot inspection, interview investigation, water quality monitoring, fish sample detection and analysis, pollutant investigation and meteorological analysis, it was preliminarily found that the cause of death of cultured fish in cages in Gutian section of Minjiang River was due to the low dissolved oxygen content in the water area, and the average monitoring value was about 1.2mg/L, which led to the death of cultured fish due to lack of oxygen.

The main reasons for the low dissolved oxygen are as follows: First, before August 26, the high temperature weather above 35℃ continued in our province, which led to the high water temperature in this water area. After August 27th, 20 1 1 year, the surface water temperature of a large area of water body plummeted due to the heavy precipitation of Typhoon Nanmadu, which led to the drastic exchange between the bottom low dissolved oxygen water body and the surface water in the reservoir area, resulting in the so-called sharp drop of dissolved oxygen content.

Second, on August 30th, 20 1 1 year, the precipitation in Shuikou town and huang tian zhen area was as high as 149. 1mm and 102.3mm respectively, and the non-point source oxygen-consuming substances washed out by the rainstorm entered the water area, which aggravated the consumption of dissolved oxygen in the water body.

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