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Biochemical Oxygen Demand

Biochemical Oxygen Demand (BOD) is a measurement of the amount of dissolved oxygen used by microorganisms to decompose organic matter in water. BOD is measured by incubating a water sample for 5 days and measuring the decrease in dissolved oxygen, which indicates the amount of organic matter present. BOD is an important water quality parameter because it provides an index of how much a discharged wastewater will impact the receiving environment by depleting oxygen levels. Regulations generally limit BOD levels to 10 mg/L for direct environmental discharge and 300 mg/L for discharge to sewer systems. New UV-VIS absorbance technology allows for continuous, real-time BOD measurements by detecting light absorption by organic matter.

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120 views2 pages

Biochemical Oxygen Demand

Biochemical Oxygen Demand (BOD) is a measurement of the amount of dissolved oxygen used by microorganisms to decompose organic matter in water. BOD is measured by incubating a water sample for 5 days and measuring the decrease in dissolved oxygen, which indicates the amount of organic matter present. BOD is an important water quality parameter because it provides an index of how much a discharged wastewater will impact the receiving environment by depleting oxygen levels. Regulations generally limit BOD levels to 10 mg/L for direct environmental discharge and 300 mg/L for discharge to sewer systems. New UV-VIS absorbance technology allows for continuous, real-time BOD measurements by detecting light absorption by organic matter.

Uploaded by

MuhdPedotFirdaus
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© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Biochemical Oxygen Demand

(BOD)
What is BOD?

Biochemical Oxygen Demand or Biological Oxygen Demand, is a measurement of


the amount of dissolved oxygen (DO) that is used by aerobic microorganisms when
decomposing organic matter in water.

How is BOD measured?

The most common approved method for determination of Biochemical Oxygen


Demand is Standard Methods 5210B. A sample is first analyzed and conditioned to
ensure favourable growth conditions for bacteria, which may include adjustment
for pH, neutralization of residual chlorine, and/or reduction of DO in
supersaturated samples. The sample is then diluted and the appropriate amount of
seed bacteria added. The initial dissolved oxygen content is recorded and the
sample is then incubated for 5 days at 20C. After the 5 day period, the sample is
removed from the incubator and the final dissolved oxygen reading is taken. BOD is
calculated from the DO depletion and volume of sample used following the formula
below:

BOD5 = BOD mg/L = [(IDO -DO5) seed correction] x dilution factor


Why is BOD important?

Biochemical Oxygen Demand is an important water quality parameter because it


provides an index to assess the effect discharged wastewater will have on the
receiving environment. The higher the BOD value, the greater the amount of
organic matter or food available for oxygen consuming bacteria. If the rate of DO
consumption by bacteria exceeds the supply of DO from aquatic plants, algae
photosynthesis or diffusing from air, unfavourable conditions occur. Depletion of
DO causes stress on aquatic organisms, making the environment unsuitable for life.
Further, dramatic depletion can lead to hypoxia or anoxic environments. BOD is
also used extensively for wastewater treatment, as decomposition of organic waste
by microorganisms is commonly used for treatment.
Regulations for BOD will vary by country and region. In general, maximum
allowable concentration for direct environmental wastewater discharge fall around
10 mg/L BOD and maximum allowable concentrations for discharge to sewer
systems around 300 mg/L BOD.

Measuring BOD with UV-VIS Absorbance technology

While the Biochemical Oxygen Demand test provides the most relevant information
for environmental impact and wastewater treatment, it provides little to no value
from an operational perspective due to the length of the test.

Using UV-VIS absorbance technology, real-time continuous results of BOD can be


achieved. Organic matter naturally absorbs light in the 200-400 nm range. Using
multiple wavelengths for

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