Biochemical Oxygen Demand – Affecting Factors and Significance

Biochemical Oxygen Demand (BOD) stands for biochemical oxygen demand, and it refers to the amount of oxygen required by microorganisms to break down organic matter in water. In the field of environmental science, one principal factor that helps us in measuring water quality is Biochemical Oxygen Demand (BOD). BOD helps us to understand the level of pollution and its effects on aquatic life. This article covers Biochemical Oxygen Demand (BOD), the significance of BOD, Measurement of BOD, Factors Affecting BOD, Effects of High BOD, and Methods to Reduce BOD in detail.

What is Biochemical Oxygen Demand (BOD)?

Biochemical Oxygen Demand (BOD) can be defined as the amount of dissolved oxygen required by microorganisms to digest organic waste present in one liter of water. The more organic waste dissolved per liter, the more the BOD. It is an important parameter used to measure the amount of pollution in water bodies. BOD is used as an indicator of water quality and thus it is important to study BOD in environmental science.

Importance of Biochemical Oxygen Demand (BOD)

The following are the importance of biochemical oxygen demand:

• BOD helps in measuring the amount of organic matter present in soils, sewages, sediment, garbage, sludge, etc.
• Measuring BOD levels helps in identifying polluted water sources and implementing appropriate measures to clean them. BOD plays an important role in determining the health of aquatic ecosystems. High levels of BOD indicate the presence of pollutants in water bodies, which can lead to a decrease in dissolved oxygen and harm aquatic plants and animals. 
• It also plays a major role during the secondary treatment of water in Sewage Treatment Plants (STPs). During secondary treatment, aerobic bacteria and fungi grow by consuming the organic waste present in water in an aeration tank and together form a mass known as Floc. When the amount of Dissolved Oxygen (DO) becomes constant in the aeration tank, it means that BOD becomes zero and no more oxygen is getting consumed and effluent along with floc is sent into the settling tank
• It also helps in measuring the rate of respiration in organisms. 
• It also plays a major role in the medicinal & pharmaceutical industries. 

How BOD is measured?

In BOD test, a water sample is collected and incubated in a controlled environment for a specific duration. The dissolved oxygen concentration is measured at the beginning and end of the incubation period. The difference between the initial and final dissolved oxygen levels gives the amount of oxygen used and this is the value of BOD. 

Factors Affecting Biochemical Oxygen Demand

BOD is affected by the following factors:

• Temperature: Higher temperatures fastens the decomposition process, which leads to an increase in BOD. 
• pH Level: Extreme pH values can affect the metabolic activities of microorganisms, which, in turn, affects BOD. 
• Amount of organic matter: The type and concentration of organic and inorganic substances in water affect BOD levels.

Effects of High Biochemical Oxygen Demand

Increased BOD levels in water bodies adversely affect aquatic life. The excessive consumption of dissolved oxygen by microorganisms during organic matter decomposition results in oxygen depletion. The decreased oxygen levels harm aquatic life. Also, high BOD levels help in the growth of algal blooms, which further deteriorate water quality. Overall, it has adverse effects on biodiversity.

Methods to Reduce Biochemical Oxygen Demand

Efforts to reduce BOD levels are crucial for maintaining the ecological balance of water bodies. Some methods are as follows:

• Sewage treatment plants: They help in removing organic waste from water before discharging it into water bodies.
• Agricultural practices: Reducing the use of chemical fertilizers and pesticides helps in reducing organic waste in water sources.
• Industrial effluent treatment: Industries must treat their wastewater properly to reduce the release of organic pollutants into water bodies.

Significance of BOD

There are many importance of BOD which are listed below:-

1. Sewage treatment plants are the main locations where BOD is important. It provides the rate at which waste, sludge, sewage, and soil respire.
2. It also plays an important role in measurement of rate of respiration of living beings.
3. BOD also helps in measuring COD
4. BOD also aid in measuring oxygen rate of cell cultures.
5. BOD is act as a water pollution indicator.

Sources of BOD

1. Water pollution is the major cause of increase BOD.
2. Pharmaceutical industries and other chemical industries led to BOD.
3. Food processing, paper mills and dye industries led to BOD.
4. Soil erosion, plant and animal waste led to BOD.
5. Phosphate in water increases BOD.

Conclusion

BOD is an important indicator of water pollution. Measuring and controlling BOD levels are essential for maintaining the health of aquatic ecosystems. By implementing effective wastewater treatment practices, adopting sustainable agricultural methods, and regulating industrial effluent discharge, we can reduce the harmful effects of high BOD levels on the environment.

FAQs on Biochemical Oxygen Demand

Q1: What is Biochemical Oxygen Demand and its importance?

BOD signifies the oxygen needed for bacteria to break down organic material in water. Discharging organic material into natural waters accelerates microorganism growth, depleting oxygen essential for other aquatic life.

Q2: What is the normal range of BOD?

Drinking water typically maintains a BOD level of 1-2 ppm. Water with a BOD value between 3-5 ppm is considered moderately clean, while polluted water falls within the range of 6-9 ppm, indicating the presence of organic waste.

Q3: What are the disadvantages of BOD?

The five-day test for BOD uses discrete samples, but it has poor reproducibility and can be affected by toxic chemicals, leading to measurement inhibition. Short-term BOD determinations amplify errors and still demand relatively long sample periods.

Q4: Why is BOD harmful?

Higher BOD values indicate a faster depletion of oxygen in the stream, reducing availability for higher forms of aquatic life. Elevated BOD leads to the same consequences as low dissolved oxygen: stress, suffocation, and death among aquatic organisms.

Q5: Why is BOD high in wastewater?

BOD measures the organic matter in water, rising with the addition of decaying plants, human or animal waste, and other organic compounds.