Bod analysis schematic diagram

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A Schematic diagram of the procedure in BOD analysis
(Note that some steps may not be presented explicitly)

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Bod analysis schematic diagram

  1. 1. BOD ANALYSIS SCHEMATIC DIAGRAM Janine V. Samelo BSChem4 Cental Luzon State University
  2. 2. sample s Pre-treatment Satisfy requirements? adjustmentsadjustments Proceed to the analysis yes Check Laboratory DO to determine the % dilution needed for each sample Check pH Check if chlorinated
  3. 3. sample s Check Laboratory DO to determine the % dilution needed for each sample Shake at least 20 times Fill BOD bottles with sample up to the neck Add 1 ml manganese solution 1 mL alkali potassium iodide azide Discard 100 mL Add starch and titrate Remarks: the higher DO, make more dilutions v v Add 1 mL sulfuric acid shake
  4. 4. sample sCheck the pH Add 1 N NaOH until pH becomes 7.0 or near Add 1 N H2SO4 until pH becomes 7.0 or near 6.5-7.2? No change in color no yes Proceed to the analysis Transfer at least 50 mL sample in a small beaker Check pH at 20 C < 6.5 > 7.2 7.0 ? no yes Note the volume needed to neutralize the aliquot and using ratio, compute the volume needed for the whole sample
  5. 5. sample s Check if chlorinated Pipet out 100 mL sample + 10 mL 1-> 50 H2SO4 10 mL KI and 4 drops starchBlue/black color chlorinated not chlorinated Titrate until the blue color disappears Note the volume needed to neutralize the 100 mL aliquot and using ratio, compute the volume needed for the whole sample Neutralized ? No change in color no yes Proceed to the analysis
  6. 6. ANALYSIS PROPER
  7. 7. Add nutrientsPrepare dilution water Aerate for 30 minutes using vacuum air pump Prepare 2 sets of BOD bottles, usually 3 for each sample (depending upon the number of dilution). Include some for blank ,seed correction and Quality control. One is for the initial measure of Do and the other for the final reading of DO Fill the ¾ of the bottles with the dilution water
  8. 8. Add volume of sample in each dilution , 3 mL seed and dilute to the mark. Stopper the bottles Add 1 ml manganese solution 1 mL alkali potassium iodide azide Discard 100 mL of the liquid Shake at least 20 times Add 1 mL sulfuric acid shake
  9. 9. Add starch and titrate with sodium thiosulfate Incubate the 2nd set of BOD Bottles covered with stopper and aluminum foil at 20 C Calculations* *via worksheet program of computer The endpoint is marked with color change from blue to clear

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