Microbes in Sewage Treatment and Biogas
Primary and secondary treatment, flocs, activated sludge and methanogens. (Biology › Microbes in Human Welfare, NEET UG syllabus.)
What is Microbes in Sewage Treatment and Biogas?
The amount of oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria. It is a measure of the organic pollution load in water.
Key formula / rule: Biochemical Oxygen Demand (BOD)
Key points
- Describe the stages of sewage treatment (primary and secondary).
- Explain the role of microbes in reducing BOD during secondary treatment.
- Define BOD and explain its significance.
- Identify the components of flocs and activated sludge.
Common exam trap
Confusing primary and secondary treatment processes.
Definitions
- Term
Biochemical Oxygen Demand (BOD)
- Meaning
The amount of oxygen that would be consumed if all the organic matter in one liter of water were oxidized by bacteria. It is a measure of the organic pollution load in water.
- Term
Flocs
- Meaning
Masses of aerobic bacteria associated with fungal filaments that grow in aeration tanks during secondary sewage treatment, consuming organic matter.
- Term
Activated Sludge
- Meaning
The settled microbial flocs from the secondary treatment effluent, a small part of which is used as an inoculum for the next batch of primary effluent.
- Term
Methanogens
- Meaning
A group of anaerobic bacteria (e.g., *Methanobacterium*) that produce methane as a metabolic byproduct, crucial for biogas production.
- Term
Biogas
- Meaning
A mixture of gases, primarily methane, produced by the anaerobic decomposition of organic matter by methanogens, used as a fuel.
Learning objectives
Describe the stages of sewage treatment (primary and secondary).
Explain the role of microbes in reducing BOD during secondary treatment.
Define BOD and explain its significance.
Identify the components of flocs and activated sludge.
Explain the process of biogas production.
Identify the key microbes (methanogens) involved in biogas production.
List the main constituents of biogas.
Formulae
- Name
Biochemical Oxygen Demand (BOD)
- Note
Higher BOD indicates higher organic pollution.
- Expression
BOD = Amount of O2 consumed by microbes to oxidize organic matter in 1L of water.
Prerequisites
Basic understanding of microorganisms (bacteria, fungi).
Knowledge of organic compounds and their decomposition.
Concept of aerobic and anaerobic respiration.
Common mistakes
Confusing primary and secondary treatment processes.
Misunderstanding BOD as a measure of oxygen *present* rather than oxygen *consumed*.
Incorrectly identifying the type of microbes (aerobic vs. anaerobic) at different stages.
Forgetting the complete composition of biogas.
Not recognizing the role of activated sludge as an inoculum.
Keywords
Sewage
Wastewater
Primary Treatment
Secondary Treatment
Aeration Tank
Flocs
BOD
Activated Sludge
Anaerobic Digester
Biogas
Methane
Methanogens
Pollution
Renewable Energy
Practice preview
What is the primary method of sewage treatment that involves the physical removal of large and small particles?…
easy
The main purpose of secondary treatment in sewage is to significantly reduce the:…
easy
Which of the following microorganisms are primarily responsible for the production of biogas in anaerobic sludge digesters?…
medium