E-mail: michael@shboqu.com   |   Expert in Water Quality Measurement and Water Treatment Project

Chemical oxygen demand you don't know

by:BOQU     2021-05-02


What is chemical oxygen demand, I must have heard a lot, but how many people really understand COD? In fact, COD (chemical oxygen demand): under certain conditions, use a certain amount of oxidizer consumed when a strong oxidizer treats a water sample.

1. What does the chemical oxygen demand reflect?

It reflects the degree of material pollution in the water. The greater the chemical oxygen demand, the more severe the pollution of organic matter in the water.

2. What is the unit of chemical oxygen demand?

COD is indicated in mg/L. The COD value detected by water quality monitoring equipment can be divided into five major categories. Among them, the first and second COD are 15mg/L, which can basically reach the drinking water standard, and the value is greater than the second category. If the water cannot be used as drinking water, the third type of COD 20mg/L, the fourth type of COD 30mg/L, and the fifth type of COD 40mg/L are polluted water quality. The higher the COD value, the more severe the pollution.

3. Does the chemical oxygen demand only reflect the organic matter in the water? In fact, COD (Chemical Oxygen Demand) is not only a single-reaction response to the organic matter in water, it can also indicate inorganic substances with reducing properties in the water, such as sulfides, ferrous ions, and sodium sulfite. For example, if ferrous ions in sewage are not completely removed in the neutralization tank, there are ferrous ions in the effluent from the biochemical treatment, and the COD (chemical oxygen demand) of the effluent may exceed the standard.

4. Advantages of fast COD tester cod detection:

(1), time-saving

The whole measurement process, including the steps of water sample digestion, colorimetric determination, etc., is short of 30 minutes; the instrument comes with 20 standard curves that can be modified and saved by yourself

(2), the secondary pollution to the environment is small

The amount of reagent is one-tenth of that of the reflux method, and the amount of waste liquid is extremely small; the instrument can automatically calculate and store 10 regression fitting curves

(3), safe and reliable

The digestion device has a blowout prevention maintenance, which can effectively prevent the water sample overflow caused by the poor acid concentration; print current data and all stored historical data

(4), can accurately store 4000 measurement results (including watch time, call curve, value), simple operation, and easy to learn

The operation guide with both pictures and texts is convenient to master COD analysis methods in a relatively short period of time;

(5), active correction function, the transmission of current data and all stored historical data to the computer, active adjustment of the digestion temperature with the number of loads to control the constant temperature, achieving true constant temperature control.

(6). Active constant temperature reminder, active countdown reminder, punctual time can be adjusted and saved at will, 3 sets of independent punctual system, can be operated by 3 people (user selectable), can be expanded to advanced intelligent spectrophotometer Measure more than 30 parameters by photometric method, large-screen LCD display, Chinese interface, Chinese key operation.

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