Bod analysis schematic diagram
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Transcript of Bod analysis schematic diagram
BOD ANALYSISSCHEMATIC DIAGRAM
Janine V. SameloBSChem4Cental Luzon State University
samples Pre-treatment
Satisfy requirements?
adjustmentsadjustments
Proceed to the analysis
yes
Check Laboratory DO to determine the % dilution needed for each sample
ACheck pH B
Check if chlorinated
C
Asamples
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
vv
Add 1 mL sulfuric acidshake
samplesCheck 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
B
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
samples
Check if chlorinated
Pipet out 100 mL sample
+ 10 mL 1-> 50 H2SO410 mL KI and 4 drops starchBlue/black
colorchlorinated
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
C
ANALYSIS PROPER
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
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 acidshake
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