Primary Treatment of Sewage
Physical removal of large and small particles from sewage through filtration and sedimentation.
What is Primary Treatment of Sewage?
Wastewater containing human excreta, domestic waste, and industrial effluents.
Key points
- To understand the purpose of primary sewage treatment.
- To identify the physical processes involved (screening, sedimentation).
- To recognize the equipment used (bar screens, grit chambers, primary clarifiers).
- To appreciate the outcome of primary treatment in terms of solid removal.
Common exam trap
Confusing primary treatment with secondary (biological) treatment.
Definitions
- Term
Sewage
- Meaning
Wastewater containing human excreta, domestic waste, and industrial effluents.
- Term
Screening
- Meaning
A process of removing large floating objects from sewage using screens.
- Term
Sedimentation
- Meaning
The process of allowing solid particles to settle out of a liquid by gravity.
- Term
Primary Clarifier
- Meaning
A large tank where sewage is held to allow suspended solids to settle out.
- Term
Sludge
- Meaning
The solid material that settles at the bottom of a sedimentation tank during sewage treatment.
- Term
Scum
- Meaning
The layer of light material (like grease and oil) that floats to the surface in a sedimentation tank.
- Term
BOD (Biochemical Oxygen Demand)
- Meaning
The amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period.
Learning objectives
To understand the purpose of primary sewage treatment.
To identify the physical processes involved (screening, sedimentation).
To recognize the equipment used (bar screens, grit chambers, primary clarifiers).
To appreciate the outcome of primary treatment in terms of solid removal.
Prerequisites
Basic understanding of water and its properties.
Concept of suspended and dissolved solids.
Knowledge of gravity and sedimentation.
Common mistakes
Confusing primary treatment with secondary (biological) treatment.
Underestimating the importance of physical separation.
Not understanding the role of gravity in sedimentation.
Forgetting that primary treatment only partially cleans the sewage.
Keywords
Sewage treatment
Primary treatment
Physical process
Screening
Sedimentation
Primary clarifier
Sludge
Scum
BOD reduction
Wastewater management
Practice preview
Which of the following processes is primarily involved in the primary treatment of sewage?…
easy
The main objective of primary sewage treatment is to remove:…
easy
Which of the following is a common method used in primary sewage treatment to separate solids from liquids?…
easy