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The BOD detection method can be mainly summarized by the following four points

by:BOQU     2022-03-16

BOD detection method is a comprehensive index to express the content of organic matter and other aerobic pollutants in water. It shows the total amount of dissolved oxygen in the water consumed when the organic matter in the water is oxidized and decomposed by the biochemical action of microorganisms to make it inorganic or gasified, and its unit is expressed in ppm (mg/L).

BOD detection method definition:

The degradation of organic matter by microorganisms is related to temperature. Generally, the suitable temperature is 15 to 30 °C, so 20 °C is generally used as the standard temperature for the determination of biochemical oxygen demand. Under the condition of BOD measurement at 20°C, the oxidative decomposition process of organic matter can basically be basically completed in 20 days. That is to say, it takes 20 days to measure the biochemical oxygen demand in the phase, which is difficult to achieve in practice. To this end, a standard time is specified, generally 5 days as the standard time for measuring BOD, so it is called the five-day biochemical oxygen demand, which is expressed as BOD5. BOD5 is about 70% of BOD20.

BOD detection methods include:

1. Standard dilution method: This method is a classic and commonly used method. Simply put, it is to measure the difference in dissolved oxygen in the solution before and after incubation at 20±1°C for five days. The obtained BOD value is called '5-day biochemical oxygen demand (BOD5)'.

2. Manometric method: In a closed culture bottle, the dissolved oxygen in the water sample is consumed by microorganisms, and the microorganisms generate CO2 equivalent to the oxygen consumption due to respiration. When CO2 is absorbed, the pressure of the closed system is reduced, According to the pressure drop measured by the pressure, the BOD value of the water sample can be obtained. BOD detection method

3. Activated sludge aeration degradation method: control the temperature to 30℃-35℃, use activated sludge for forced aeration to degrade the samples for 2 hours, digest the biodegraded samples with potassium dichromate, and measure the samples before and after biodegradation stoichiometric oxygen demand, the difference is BOD. According to the comparative experimental results with the standard method, it can be converted into a BOD5 value.

4. Biosensor method: The principle is to make the water sample and air enter the flow cell to contact the microbial sensor at a certain flow rate. When the diffusion rate of the soluble and degradable organic matter in the water sample is constant by the biofilm, the quality of oxygen diffused to the surface of the oxygen electrode is also constant and a constant current is generated. Since the difference between the current and the biodegradable organic matter in the water sample has a quantitative relationship with the reduction of oxygen, the water sample can be calculated accordingly. Biochemical oxygen demand. Usually, the BOD5 standard sample is used for comparison to converting the BOD5 value of the water sample.

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