Water is passed through filters of sand, charcoal, and gravel to remove impurities and make it cleaner. Here's a breakdown of why:
How Sand, Charcoal, and Gravel Filtration Works
These materials work together to create a multi-layered filtration system that removes different types of contaminants from the water. The filtration process leverages the physical properties of each layer to trap and retain unwanted particles. The sand, gravel and charcoal function as different layers that each have a part to play in the overall process of water filtration.
Sand Filters
- How it works: The sand filter works by distributing the unfiltered water across the top layer. The water then slowly sinks through the sand.
- Function: According to the provided reference, "The small pores ensure that the dirt particles are not able to pass through and retain the dirt particles."
- Main Use: Primarily used to remove small particulate matter like sediment and silt.
Gravel Filters
- How it Works: The gravel layer often forms the bottom of a filter, providing larger spaces through which water can initially flow.
- Function: Gravel is used to separate larger dirt particles and ensure water is distributed evenly.
- Main Use: Used to trap larger contaminants and assist with drainage.
Charcoal Filters
- How it Works: Typically the charcoal layer is located in the middle of the filter.
- Function: Charcoal (specifically activated charcoal) is excellent at adsorbing impurities, including chemicals and chlorine, due to its large surface area.
- Main Use: Primarily used to remove bad tastes, odours, chlorine, and certain organic compounds.
Combined Benefits
When used together, these three materials form a robust system:
- Initial Coarse Filtration: Gravel acts as the first layer to remove the largest particles.
- Fine Particle Removal: Sand then filters out the smaller particles that passed through the gravel.
- Adsorption of Chemicals and Odors: Finally, charcoal removes remaining chemicals, odors, and tastes, resulting in cleaner and more palatable water.
Summary
| Filter Material | Purpose |
|---|---|
| Gravel | Removes large particles and assists with drainage |
| Sand | Traps small particles, like dirt and silt. |
| Charcoal | Absorbs chemicals, chlorine, bad odors, and improves taste |
Therefore, water is passed through sand, charcoal, and gravel filters to effectively remove different types of impurities, ranging from large particulate matter to chemicals, thereby enhancing its quality and making it safer for consumption or other uses.
