BOD

BOD or Biochemical Oxygen Demand is a measure of the quantity of oxygen used by microorganisms (e.g., aerobic bacteria) in the oxidation of organic matter.

Introduction

Biochemical Oxygen Demand (BOD) is a key indicator of the organic quality of water. It measures the amount of oxygen required by aerobic microorganisms to decompose the organic matter in a sample of water, such as that polluted by sewage or industrial waste. The BOD value is most commonly expressed in milligrams of oxygen consumed per litre of sample during 5 days of incubation at 20 °C and is often used as a surrogate of the degree of organic pollution of water.

Measurement of BOD

BOD can be measured directly by using an oxygen probe or indirectly by titration methods. The direct method involves the measurement of the amount of oxygen consumed by the microorganisms during a specified time interval. The indirect method involves the addition of an excess amount of an oxidizing agent (like potassium dichromate in an acidic medium) to the sample of water. The remaining unreacted oxidizing agent is then titrated with a reducing agent to determine the amount of oxidizing agent that has reacted with the organic matter.

Applications of BOD

BOD is used extensively in the water industry and environmental science. It is used in water quality management and assessment, wastewater treatment, and is an important parameter in the design and operation of wastewater treatment plants. It is also used in the assessment of the efficiency of treatment processes and in the determination of the organic strength of wastes.

Limitations of BOD

While BOD is an important parameter in water quality assessment, it has its limitations. It is not a precise quantitative test, although it is widely used as an indication of the organic quality of water. The test has a low reproducibility, and the results are often not comparable between different laboratories due to differences in the microbial populations and in the interpretation of the results.

See also

• Chemical Oxygen Demand
• Total Organic Carbon
• Water Quality
• Wastewater Treatment