Understanding Biological Oxygen Demand (BOD) in Water
The question asks about what type of organism requires the dissolved oxygen measured by Biological Oxygen Demand (BOD) in water. BOD is a key parameter used to assess the quality of water, particularly its organic pollution level.
What is Biological Oxygen Demand (BOD)?
Biological Oxygen Demand (BOD) is defined as the amount of dissolved oxygen (DO) required by aerobic biological microorganisms to break down organic material present in a given water sample at a specific temperature over a set time period. Essentially, it measures how much oxygen is consumed by these organisms while they decompose organic matter.
Why Microbes are Key to BOD
The primary decomposers of organic waste in water bodies are microorganisms, mainly bacteria. These microbes utilize dissolved oxygen during the aerobic respiration process to metabolize complex organic substances into simpler, more stable inorganic compounds. The more organic pollution there is in the water, the more active these microbes become, and consequently, the more dissolved oxygen they consume. Therefore, a high BOD value indicates a large amount of organic pollution and a high demand for oxygen by microbes.
Let's look at why the other options are not the correct answer in the context of BOD measurement:
- Plants: Aquatic plants produce oxygen during photosynthesis in the presence of sunlight. While they also consume some oxygen during respiration (especially at night), the BOD test specifically measures the oxygen consumed by decomposition of organic matter, which is primarily done by microbes.
- Animals: Aquatic animals like fish and invertebrates consume dissolved oxygen for respiration. However, the BOD test is not designed to measure the oxygen demand of macro-organisms. It focuses on the oxygen consumed by microbial decomposition of organic pollutants.
- Seaweeds: Seaweeds are large multicellular algae, a type of plant life in marine environments. Like other plants, they produce oxygen through photosynthesis and consume it through respiration. Their oxygen consumption is not what the standard BOD test primarily measures, which targets microbial activity on organic pollutants.
Based on the definition and standard procedure of the Biological Oxygen Demand test, the dissolved oxygen is required by the microbes to decompose organic waste.
Therefore, the biological oxygen demand is the amount of dissolved oxygen required by Microbes in water.
| Component | Role in BOD |
|---|---|
| Dissolved Oxygen (DO) | Oxygen available in water for organisms. |
| Organic Matter | Pollutants broken down by microbes. |
| Microbes (Bacteria) | Organisms that consume DO to decompose organic matter. |
| BOD Value | Measure of oxygen consumed by microbes over time. |
Revision Table: Key Concepts
| Term | Explanation |
|---|---|
| BOD | Biological Oxygen Demand - oxygen needed by microbes to decompose organic waste. |
| DO | Dissolved Oxygen - oxygen available in water. |
| Aerobic Respiration | Process used by microbes consuming oxygen to break down organic matter. |
| Water Quality | BOD is an indicator of organic pollution and its impact on oxygen levels in water. |
Additional Information: Factors Affecting BOD
Several factors can influence the Biological Oxygen Demand measured in a water sample:
- Amount of Organic Matter: More organic pollutants lead to higher microbial activity and thus higher BOD.
- Temperature: Microbial activity is highly dependent on temperature. BOD tests are typically conducted at a standard temperature (e.g., 20°C).
- Presence of Microbes: The sample must contain active aerobic microorganisms capable of decomposition.
- Time Period: BOD is measured over a specific time, commonly 5 days (BOD<sub>5</sub>).
- Presence of Inhibitors: Toxic substances in the water can inhibit microbial activity, leading to an underestimation of the true organic load.
BOD is a crucial test in environmental monitoring, wastewater treatment, and assessing the health of aquatic ecosystems.
Important Questions from Miscellaneous
A stone is thrown horizontally from the top of a 20 m high building with a speed of 12 m/s. It hits the ground at a distance R from the building. Taking g = 10 m/s2 and neglecting air resistance will give :
A mass is attached to a spring that hangs vertically. The extension produced in the spring is 6 cm on Earth. The acceleration due to gravity on the surface of the Moon is one-sixth of its value on the surface of the Earth. The extension of the spring on the Moon would be:
Directions: Each item in this section consists of a sentence with an underlined word followed by four words (a), (b), (c), and (d). Select the option that is opposite in meaning to the underlined word and mark your response in your Answer Sheet accordingly.
The deluge affected the population.The major source of vitamins and minerals for vegetarians is
Which of the following statements about the Deccan Riots Commission is/are correct?
1. The Commission did not hold enquiries in the districts which were not affected.
2. The Commission did record the statements of ryots, sahukars and eye-witnesses.
Select the correct answer using the code given below:
