Heavy mineral material found in raw sewage is called:
grit
Sewage Grit Material Explained
Raw sewage, the wastewater generated from homes and industries, contains a mixture of solid materials. Among these are inorganic, heavy materials that tend to settle quickly when the flow rate decreases. This specific type of material is referred to as grit.
Understanding Grit Composition
Grit in sewage primarily consists of abrasive mineral elements. Common components include:
- Sand
- Silt
- Gravel (small particles)
- Cinders
- Bone fragments
- Eggshells
- Coffee grounds
- Other small, heavy, inorganic materials
These materials are denser than the organic solids typically found in sewage, causing them to settle out rapidly in sedimentation tanks or grit chambers designed for their removal.
Why Grit is Removed
Grit removal is a crucial primary stage in wastewater treatment. If not removed, grit can:
- Cause abrasion and wear on mechanical equipment like pumps and screens.
- Accumulate in tanks and channels, reducing capacity and increasing maintenance costs.
- Interfere with downstream treatment processes.
Analyzing Other Options
Let's look at why the other options are less accurate:
| Option | Description | Relevance to Question |
|---|---|---|
| Gravel | Typically refers to larger stones, usually larger than 2 mm (millimetres) in diameter. While small gravel can be part of grit, it's not the specific term for the entire heavy fraction. | Partially correct, but 'grit' is the broader, more specific term used in sewage treatment for the settled heavy minerals. |
| Silt | Refers to fine particles, typically smaller than sand (0.004 to 0.0625 mm). Silt can be a component of grit, but grit also includes coarser materials like sand. | A component of grit, but not the overarching term for all heavy mineral material. |
| Glass | While glass fragments can be present in sewage, they are just one type of inorganic material. 'Grit' encompasses a wider range of heavy mineral materials. | Can be present, but not the general term for the heavy mineral fraction. |
Therefore, grit is the most appropriate and specific term for the heavy mineral material found in raw sewage.
Important Questions from Sewage
Which of the given options are NOT listed as a type of sewer appurtenances?
BOD stands for
If 2% solution of a sewage sample is incubated for 5 days at 20° C and depletion of oxygen was found to be 5 ppm, BOD of the sewage is
Aerobic bacteria combining with oxygen is called:
Thermochemical decomposition of organic materials at high temperatures, in the absence of oxygen is called
