Q13064 - INFO: BOD Manager Example Calculations pptx

Article ID: Q13064

Created Date: 6/22/2010 9:48 AM

Last Modified: 6/22/2010 9:48 AM

Author: Scott Dorner

Original URL: http://www.opssys.com/instantkb/article.aspx?id=13064

BOD Example Calculations

The method consists of filling an airtight bottle with a sample. The bottle is a specified size and filled to

overflowing. The sample is incubated at constant temperature for five days. Dissolved oxygen (D.O.) is measured

by probe before and after incubation. BOD is computed based on the difference between initial and final D.O.

The test uses dilution water and a known amount of sample in a 250-300 ml incubation bottle. A small amount of

seed is added to samples where microbial activity may not be present. The initial D.O. is measured by probe and

the bottle is stored at 20 °C. After five days, final D.O. is measured. If no seed is used, the BOD of the bottle is

computed using Equation 1.

BOD = IDO - FDO (Eq. 1)

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

When seed is added, seed control tests must be done to determine the amount of oxygen depleted by the seed.

Calculation of BOD includes a correction factor for seed as expressed by Equation 2.

BOD = (IDO - FDO) - (Cavg * SV) (Eq. 2)

VS / VB

where:

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

FDO = final D.O. of diluted sample, 0 mg/L

VS = volume of sample, ml

VB = volume of bottle, ml

Cavg = correction factor for oxygen depletion resulting from presence of seed

SV = Volume of Seed added to Sample in ml.

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