 # BOD (Seeded,Unseeded) Calculator

This page has two recognized calculation methods(seeded,unseeded) for the measurement of dissolved oxygen for BOD.

## Why BOD test is conducted for 5th day

BOD theoretically takes infinite time to go to completion because the rate of oxidation is assumed to be proportional to the amount of organic matter remaining.

Within 20day period the oxidation of carbonaceous matter is about 95 to 99% and in 5 days it is 60 to 70%

20 days is long time to wait for test.

After 8 to 10 days nitrifying bacteria start using oxygen to convert ammonia nitrogen to nitrite and then to nitrate. ## BOD Using Dilution Method

Biochemical oxygen demand(BOD) is the amount of dissolved oxygen needed by aerobic biological organisms.Dilution method is a standard method and it is recognized by EPA.

BOD5 is calculated by:

Unseeded BOD5 = (D0 - D5)P

Where,

D0 is the dissolved oxygen (DO) of the diluted solution after preparation (mg/l)

D5 is the DO of the diluted solution after 5 day incubation (mg/l)

P is the decimal dilution factor

Seeded BOD5 = (D0 - D5) - ( (B0 - B5) × f )P

Where,

D0 is the dissolved oxygen (DO) of the diluted solution after preparation (mg/l)

D5 is the DO of the diluted solution after 5 day incubation (mg/l)

D0 is the dissolved oxygen (DO) of the diluted solution after preparation (mg/l)

D5 is the DO of the diluted solution after 5 day incubation (mg/l)

P is the decimal dilution factor

B0 is the DO of diluted seed sample after preparation (mg/l)

B5 is the DO of diluted seed sample after 5 day incubation (mg/l)

f is the ratio of seed volume in dilution solution to seed volume in BOD test on seed

## Why BOD test

Measure the amount of oxygen required to stabilize organic matter biologically.

Measure the effeciency of treatment facility.

Determine compliance with waste water discharge permits.

### More Calculators ► 