BOD5 analyzer is an instrument for measuring biological oxygen demand (BOD) in water. BOD5 refers to the amount of oxygen required by microorganisms in water to release carbon dioxide by using organic substances for respiration under standard conditions within 5 days. The principle is to use the microorganisms existing in the water to bio-absorb the organic matter in the water sample, and then consume the dissolved oxygen in the water, and finally calculate the BOD5 value by comparing the consumption of dissolved oxygen.
The calibration steps of BOD5 tester are as follows:
1. Equipment preparation: prepare the BOD5 tester and its supporting equipment, including electronic scales, containers and timers.
2. Sample preparation: collect clear, odor-free and sundry-free water samples from the water source, filter them and store them in sterile containers. In the BOD5 test, the sample needs to allow microorganisms to grow in water, so the sample should not contain strong disinfectants or toxic organic substances.
3. Container preparation: prepare the BOD test container. Before filling, it is necessary to disinfect the inner wall of the bottle with nitric acid or chloroform, and pay attention to cleaning the bottle mouth.
4. Sample filling: fill the BOD test container. It is usually carried out at 37 ° C. Fill 2/3-3/4 of water in each sample bottle, then add 1ml of potassium chromate and 5ml of nutrient solution, mix and dilute the sample. This nutrient solution can effectively promote the growth of microorganisms and make BOD5 test more accurate.
5. Heat preservation (constant temperature) of the sample: the bottle mouth is equipped with a rubber stopper, and then the bottle is placed in a constant temperature bath, and the temperature is adjusted to 37 ° C. Dissolved oxygen is measured at a fixed time interval (usually 5 days).
6. Dissolved oxygen measurement: measure the dissolved oxygen of water sample in a closed environment. The BOD5 value is calculated by comparing the dissolved oxygen content of the original water sample and the dissolved oxygen content after 5 days.
7. Calculate the BOD5 value of the sample: calculate the BOD5 value of the sample according to the initial dissolved oxygen content of the water sample and the dissolved oxygen content after 5 days. The sum of initial amount and dissolved oxygen consumption after 5 days is often set as BOD5. The correctness of the calibration results of the BOD5 tester is helpful to the accuracy of the test results, so as to better understand the quality and quantity of organic substances from natural or artificial sources in a given water source.