BOD = (IDO - FDO)/(VS/VB)

where:

IDO = initial D.O. of diluted sample, mg/L

FDO = final D.O. of diluted sample, mg/L

VS = volume of sample, ml

VB = volume of bottle, ml

BOD = biochemical oxygen demand, mg/L

Regards

I am afraid if you are doing it correctly. As per the standard procedure, you have to aerate the dilution water to its maximum capacity. Thus, there must be at least 7 mg/L of DO initially available for the BOD test.

I agree with Akshay Shende.

I suggest you should go for 50% dilution i.e., 500 ml sample + 500 ml d.w(distilled water), now your dilution factor will be 0.5.

after 50% dilution note down DO initial and after 3 days at 27 C take final DO.

BOD = (DO initial- DO final)* D.F

note: D.F (dilution factor)= 0.5.

Thank you