refers to the mass concentration of dissolved oxygen required for the biochemical process of microbial decomposition of organic matter in water under aerobic conditions. In order to make the BOD detection values comparable, a period of time is generally specified, and the consumption of dissolved oxygen in water is determined. Generally, five days are used, which is called five-day biochemical oxygen demand, recorded as BOD5, and five-day biochemical oxygen demand is often used. . The larger the BOD value, the more organic matter is contained in the water, so the pollution is more serious. BOD detection method ●Before each test, the BOD detection equipment should be kept hygienic to ensure the accuracy of the test. ★During the operation, the sample is in a constant temperature state. The temperature is around 20°C. Ensure the dissolved oxygen content in the water to reduce measurement errors. ★Adjust the pH value of the water sample ØAfter the sample reaches a constant temperature of 20°C, check the pH value of the sample with precision PH test paper (6.4-8.0). Ø The pH value of the sample should be between 6.7 and 7.5 (the optimum point is 7.2). For samples outside this range, the measured value of BOD will be small. ØIt should be neutralized with sodium hydroxide or hydrochloric acid solution, but the volume should not exceed the sample volume ★Measure an appropriate amount of water sample Øeg: the concentration range of the sample (0~20)mL, the sample sampling volume (500mL). Use a clean graduated cylinder or volumetric flask to measure the accurate sample volume, add it to wash and dry in dry culture flasks. ØThe BOD value of general water samples is estimated as 60% of the chemical oxygen demand (CODCr) and the approximate concentration range. ★Put in a magnetic stirrer, absorbent ØIncline the culture bottle slightly. Put the stirring bar into the culture bottle. Let the stirring bar slide naturally to the bottom of the culture bottle to prevent damage to the culture bottle or the stirring bar. ØUse plastic tweezers to add a little sodium hydroxide granules (usually 3~5 granules) into the medicine cup. Do not drop sodium hydroxide into the culture bottle. ★Install the test terminal ØInstall the medicine cup and BOD test terminal on the culture bottle in turn, and tighten them (especially important, it is related to the success or failure of the test). ★Put the incubator into the incubator for automatic testing ØPut the stirring tray into the incubator whose temperature has reached 20°C. Turn on the power supply of the agitating tray. Put the culture bottle with the test terminal installed on the agitating tray and close the door of the incubator. ØAfter the constant temperature waiting time expires, the test terminal will start automatic testing. ØAfter the number of test days is reached, the instrument will automatically stop the test and save the data, and view the detailed data and test results in the menu.
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