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About COD, BOD

Tyd: 2020-06-29 Hits: 28

What is COD?

COD (Chemical Oxygen Demand): Under certain conditions, the amount of oxidant consumed in the treatment of water samples with a certain strong oxidant.

COD reflects the degree of pollution in the water. The greater the chemical oxygen demand, the more serious the pollution of organic matter in the water.

COD is expressed in mg/L, and water quality can be divided into five categories:

The COD of the first category and the second category is ≤15mg/L, which can basically meet the drinking water standard, and the water with a value greater than the second category cannot be used as drinking water.

The third category of COD ≤ 20mg/L, the fourth category of COD ≤ 30mg/L, and the fifth category of COD ≤ 40mg/L are all polluted water quality. The higher the COD value, the more serious the pollution.

What is BOD?

BOD (Biochemical Oxygen Demand): Under aerobic conditions, the mass concentration of dissolved oxygen required in the biochemical process of microbial decomposition of organic matter in water.

In order to make BOD detection values comparable, a five-day cycle is generally specified, and the consumption of dissolved oxygen in the water is measured, which is called the five-day biochemical oxygen demand and is recorded as BOD5.

BOD is an environmental monitoring indicator used to monitor the pollution of organic matter in water. Organic matter can be decomposed by microorganisms. In this process, oxygen needs to be consumed. If the dissolved oxygen in the water is not enough to supply the needs of microorganisms, the water body is in a polluted state.

What is the relationship between COD and BOD?

COD (Chemical Oxygen Demand) is the amount of oxygen consumed by oxidation of sewage with chemicals, and BOD (Biochemical Oxygen Demand) is the amount of oxygen consumed by oxidation of microorganisms in sewage. More oxygen consumption means more organic pollutants in the water.

Traditionally, COD (Chemical Oxygen Demand) basically represents all organic matter in sewage, and BOD (Biochemical Oxygen Demand) represents biodegradable organic matter in sewage. Therefore, the difference between COD and BOD can represent organic matter that cannot be biodegraded in sewage.