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The correct test procedure for BOD detection method is divided into the following three steps

by:BOQU     2022-01-17

BOD detection method, BOD is the determination of biochemical oxygen demand. Together with the COD chemical oxygen demand measurement, it is one of the main indicators for judging the organic pollutants in the water body. The HM series BOD biochemical oxygen demand tester is based on the national standard ' HJ505-2009' 5-day culture method, simulating the biodegradation process of organic matter in nature, using intelligent, simple, safe, and reliable mercury-free differential pressure sensing method to measure BOD in water.

Experimental steps of BOD detection method:

1. Take water samples and repack:

a. Rinse the water sample twice with 500mL, and then slowly flow the water sample into the beaker along the wall of the beaker. It should be noted that the water flow should not be too fast and the generation of bubbles is strictly prohibited.

b. Adjust PH: Use a pH meter to adjust the pH of the water sample to the range of 6.5~7.5.

c. Dispense the water sample: Insert one end of the siphon tube into the water sample, and use the ear wash ball to siphon out the water at the other end, and then slowly flow this end of the siphon tube down the iodine measuring bottle, and first put it into the 250mL iodine measuring bottle. Rinse twice before filling; then put it into a 100mL iodine measuring bottle. There should be a water sample overflowing from the mouth of the 250mL iodine measuring bottle to ensure that there is a water seal. After that, wrap the mouth of the bottle with plastic wrap and place it in a 20°C constant temperature incubator for 5 days.

Determine the dissolved oxygen in the water sample in a 100mL iodine measuring flask:

a. Insert the pipette under the liquid surface, add 0.5 mL of manganese sulfate solution and 1.0 mL of alkaline potassium iodide solution in sequence, cover the bottle stopper, avoid air bubbles in the bottle, mix upside down 15 times, and let it stand. When the brown flocculent sediment is reduced to half, invert it several times.

b. Gently open the bottle stopper during analysis, immediately insert the pipette under the liquid surface, add 1.0 mL of concentrated sulfuric acid, carefully cover the bottle stopper, invert and mix and shake until all the precipitate is dissolved. If the dissolution is not complete, you can continue to add a small amount of concentrated sulfuric acid, but do not overflow the solution at this time. Then leave it in the dark for 5 minutes.

c. Use a straw to suck up 50mL of the above solution, pour it into a 150mL Erlenmeyer flask with a rotor, titrate with 0.025mol/L sodium thiosulfate standard solution until the solution is light yellow, add 0.5mL starch solution, pay attention to close At the endpoint, it should be dropped slowly, and the medicine remaining on the wall should be washed down with distilled water, and the titration should be continued until the blue color just faded, and the dosage V1 should be recorded.

3. Measure the dissolved oxygen in the water sample in a 250mL iodine measuring flask after five days:

a. Insert the pipette under the liquid surface, add 1.0 mL of manganese sulfate solution and 2.0 mL of alkaline potassium iodide solution in sequence, close the bottle stopper, avoid air bubbles in the bottle, mix upside down 15 times, and let it stand. When the brown flocculent sediment is reduced to half, invert it several times.

b. Gently open the bottle stopper during analysis, immediately insert the pipette below the liquid surface, add 2.0 mL of concentrated sulfuric acid, carefully cover the bottle stopper, invert and mix and shake until all the precipitate is dissolved. If the dissolution is not complete, you can continue to add a small amount of concentrated sulfuric acid, but do not overflow the solution at this time. Then leave it in the dark for 5 minutes.

c. Use a straw to suck 50mL of the above solution, inject it into a 150mL Erlenmeyer flask with a rotor, titrate with 0.025mol/L sodium thiosulfate standard solution until the solution is light yellow, add 1.0mL starch solution, pay attention to close At the endpoint, it should be dripped slowly, and the medicine remaining on the wall should be washed down with distilled water, and the titration should be continued until the blue color just faded, and the dosage V2 should be recorded.

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