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Bod analysis schematic diagram
The document outlines the procedure for conducting a Biochemical Oxygen Demand (BOD) analysis, including pre-treatment steps to ensure sample suitability. It details laboratory requirements, dilution calculations, and titration methods to assess whether the water samples are chlorinated or not. The analysis requires careful monitoring of pH levels and involves specific treatments to prepare samples for accurate oxygen demand measurement.
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Bod analysis schematic diagram
- 1. BOD ANALYSIS SCHEMATIC DIAGRAM JanineV. Samelo BSChem4 Cental Luzon State University
- 2. sample s Pre-treatment Satisfy requirements? adjustmentsadjustments Proceed tothe analysis yes Check Laboratory DO to determine the % dilution needed for each sample Check pH Check if chlorinated
- 3. sample s Check Laboratory DO todetermine 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. sample sCheck the pH Add1 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. sample s Check if chlorinated Pipet out100 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.
- 7. Add nutrientsPrepare dilutionwater 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. Add volume ofsample 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. Add starch andtitrate 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