Problem 15 - A Complete Resource Book in Chemistry for JEE Main

Question

\(\mathrm{BOD}\) is connected with (a) microbes (b) organic matter (c) both (a) and (b) (d) none of these

Step-by-Step Solution

Answer

(c) both (a) and (b)

Step 1: Understanding BOD

Biochemical Oxygen Demand (BOD) is a measure used to determine the amount of oxygen that microorganisms will consume while decomposing organic material in water.

Step 2: Evaluating Option (a)

Option (a) mentions 'microbes.' BOD is directly related to microbes because they are the ones that consume oxygen as they decompose organic matter in water.

Step 3: Evaluating Option (b)

Option (b) refers to 'organic matter.' BOD is affected by the presence of organic matter because it serves as food for microbes, which decompose it, thereby consuming oxygen.

Step 4: Evaluating Option (c)

Option (c) is 'both (a) and (b).' Since BOD involves both microbes consuming oxygen and the presence of organic matter, the correct answer would include both.

Step 5: Evaluating Option (d)

Option (d) states 'none of these,' which is incorrect because BOD is indeed connected with both microbes and organic matter.

Key Concepts

Microorganisms

Microorganisms play a critical role in the environment, especially in aquatic ecosystems. They are tiny, often single-celled organisms such as bacteria, fungi, and protists. In water bodies, microorganisms perform a vital function by breaking down organic matter. This process forms the core of the Biochemical Oxygen Demand (BOD) concept.

When microorganisms decompose organic substances, they use oxygen. Therefore, the more microorganisms present in the water, the more oxygen will be consumed. This is important because:

• It helps regulate the natural recycling of nutrients.
• It aids in breaking down pollutants in water naturally.
• It indicates the health and cleanliness of water, as excessive microorganism activity can lead to oxygen depletion.

Understanding the roles of microorganisms in BOD helps in monitoring and controlling environmental pollution. This is critical for maintaining ecological balance and for managing water resources effectively.

Organic Matter

Organic matter is essentially any carbon-containing material from living or dead organisms. In aquatic environments, organic matter becomes a significant factor due to its potential impact on water quality. It can originate from both natural sources, like fallen leaves and wildlife waste, and anthropogenic sources such as sewage and agricultural runoff.

The presence of organic matter in water provides food for microorganisms. As they break down this matter, they use the oxygen dissolved in the water, contributing to the BOD. This relationship means:

• High levels of organic matter increase BOD, leading to lower oxygen levels in water bodies.
• Oxygen depletion can stress or even kill aquatic life, especially fish and invertebrates that depend on oxygen-rich environments.
• Monitoring organic matter in water is crucial for environmental protection and pollution management.

By understanding organic matter's role in BOD, environmental scientists can better assess ecosystem health and create strategies to reduce water pollution.

Water Pollution

Water pollution is the contamination of water bodies such as lakes, rivers, oceans, and groundwater. It is often caused by human activities and can lead to significant environmental damage. One of the challenges related to water pollution is its effect on BOD.

Pollutants, especially those containing organic substances, increase BOD. When pollutants enter the water:

• The level of organic matter rises, providing more food for microorganisms.
• Increased microorganism activity depletes the oxygen available in the water.
• This depletion can harm or kill aquatic life, disrupt ecosystems, and affect water quality and usability.

Minimizing water pollution is essential. Practices such as proper waste disposal, reducing industrial discharge, and using sustainable agriculture can help control pollution and lower BOD levels. Understanding water pollution's effect on BOD highlights the need for active environmental management to protect aquatic ecosystems and ensure healthy water resources for all.