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Seed BOD calculation

                     SEED BOD CALCULATION

 

 In BOD analysis we need to seed the sample when there is no microorganism in the sample i.e. bacteria that eat the organic matter present in the sample are not there in the sample so microorganism has to be added to the sample.

We need to seed the sample only when the sample taken from waste water, we do not required seeding in the river or sewage samples because they already contain microorganism.

How to estimate BOD in sample

It is very important to select the suitable volume of sample for dilution other wise all effort will be  vail.
so here are some calculation for the estimation of BOD, once you get idea about the estimated bod in the sample then you will be able to select suitable portion of sample for dilution.

First we have to determined it's COD after that we can calculate estimated  BOD 
generally your BOD will be 70% of COD.

once you get estimated BOD calculate Volume of sample required for each BOD bottles.

you know one BOD bottle contains 300 ml sample.

Sample volume in ml, per litre dilution = (X/Estimated BOD)X1000

For keeping 2 dilutions take X = 2.5 and 4.0 
For single dilution take X = 3.0 or 3.5. 
Round off to nearest convenient volume fraction. In case of high BOD samples, prepare primary dilutions with distilled water and then make the final dilution. 
 

Example

Suppose COD of the given sample is 400 mg/L
then as per above said estimated BOD of the sample will be 70% of COD Value
i.e. 400 X70/100 = 210 mg/L


Now calculate the Sample volume in ml, per litre dilution
For d dilution X= 2.5 and 4.0
      (2.5/210) X1000 = 11.90
       i.e. 12 ml/L means 1.2 %
Here keep in mind that your BOD bottles contain only 300 ml  only, so volume of sample require for dilution will be 1.2X3= 3.6 ml 

means you required 3.6 ml sample in one BOD Bottle. 

Similarly calculate the required volume for X= 4
i.e. 19 ml /L means 1.9%










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