BOD Full Form, Importance, How to Calculate BOD?

BOD Full Form: Biochemical Oxygen Demand is also known as Biological Oxygen Demand. The full form of BOD (Biological Oxygen Demand) is the amount of dissolved oxygen that microorganisms require during the biological degradation of organic compounds in water. BOD serves as an indicator of the level of organic matter present in a sample. Additionally, Biochemical Oxygen Demand (BOD) is used to quantify organic wastewater contamination. A higher BOD value indicates a lower dissolved oxygen concentration in the water, indicating pollution.

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BOD Levels

Importance of BOD

Impacts of Elevated BOD Levels

• Reduced dissolved oxygen levels: Decreased oxygen levels in water can lead to fish kills and disturbances in aquatic life.
• Increased bacterial and algal growth: Excessive growth of bacteria and algae can result in unpleasant taste and odor issues in drinking water.
• Infrastructure clogging : Heightened bacterial and algal growth can lead to the accumulation and clogging of pipes and other infrastructure.
• Eutrophication: Excessive nutrient enrichment can induce eutrophication, which depletes animal and plant life in bodies of water.

Benefits of BOD Reduction

• Protection of aquatic life and ecosystems : High BOD levels contribute to algae blooms and oxygen depletion in water bodies, posing a threat to fish, plants, and other aquatic organisms.
• Improved water quality: By reducing BOD, overall water quality can be enhanced, making it more suitable for human consumption and various uses.
• Cost savings: Treating water with elevated BOD levels can be expensive. Lowering BOD helps minimize treatment costs, saving money in the process.
• Reduction of environmental pollution: High BOD concentrations can result in water pollution, causing harm to the environment. By reducing BOD, environmental pollution can be mitigated, ensuring the preservation of ecosystems.

Methods of BOD Reduction

• Aeration: Aeration introduces air or oxygen into wastewater, promoting aerobic bacteria growth that consumes organic materials and lowers BOD levels.
• Activated sludge process: This biological treatment method uses a mixture of wastewater, microorganisms, and oxygen in aeration tanks. The microorganisms break down organic matter, reducing BOD levels.
• Trickling filters: In this process, wastewater is trickled over a bed of rocks or plastic media, covered with a layer of biofilm containing bacteria. The bacteria consume organic matter, reducing BOD levels.
• Constructed wetlands: These engineered systems use aquatic plants and microorganisms to treat wastewater. As water passes through the wetland, plants and microorganisms, remove organic matter and BOD pollutants.
• Chemical precipitation: Chemicals such as coagulants or flocculants are added to the wastewater to form precipitates. These precipitates trap organic matter, reducing BOD levels.

How to Calculate the BOD?

• Collect a water sample: Take a representative sample to be tested. Ensure that the sample is adequately sealed and preserved to prevent any changes in oxygen levels during transportation.
• Measure initial dissolved oxygen (DO): Using a dissolved oxygen meter, measure and record the dissolved oxygen concentration in the water sample. This measurement represents the DO level at the beginning of the incubation period and is denoted as D(i).
• Incubate the sample: Place the water sample in a sealed container and incubate it in a dark area at a specific temperature, often about 20°C (68°F). This promotes the growth and activity of the microorganisms in the sample.
• Incubation period: Allow the sample to incubate for a fixed duration, typically five days. During this time, microorganisms in the water metabolise organic substances, resulting in the consumption of dissolved oxygen.
• Measure final dissolved oxygen (DO): After incubating, measure the dissolved oxygen concentration again using the dissolved oxygen meter. This measurement reflects the remaining dissolved oxygen in the water sample after microbial activity, denoted as D(f).
• Calculate BOD: The BOD can be determined using the BOD formula: BOD = (D(i) - D(f)) / P

• D(i) represents the initial dissolved oxygen concentration.
• D(f) represents the final dissolved oxygen concentration.
• P represents the volumetric fraction of wastewater.

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