At present, the national standard for determining BOD is dilution inoculation method. The BOD50 or 200 exceeds the detection line, and the water sample must be diluted before determination. Generally, before measuring a water sample, the amount of BOD is estimated according to the source of the water sample. Like ordinary natural water bodies, it can be directly measured, but the wastewater discharged by paper mills and food production enterprises is generally diluted.
meaning
Molecular oxygen dissolved in water in air is called dissolved oxygen, and the content of dissolved oxygen in water is closely related to the partial pressure of oxygen in air and the temperature of 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 dissolved oxygen content in the water. Molecular oxygen dissolved in water is called dissolved oxygen, usually referred to as DO for short, and is expressed in milligrams of oxygen per liter of water. The amount of dissolved oxygen in water is an index to measure the self-purification ability of water body.
Refer to the above content: Baidu Encyclopedia-Dissolved Oxygen