To put alum in a water tank for water treatment, you first add the alum and stir the water to dissolve the alum thoroughly. After dissolving the alum, you then allow the water to sit undisturbed for a minimum of 1 to 2 hours, but ideally for a longer period, such as overnight.
This process utilizes alum (aluminum sulfate) as a coagulant to purify water. Alum helps suspended particles clump together, making them heavy enough to settle out of the water.
Steps for Adding Alum to a Water Tank
Adding alum correctly ensures effective water clarification. Here are the key steps:
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Dissolving the Alum
- Measure the appropriate amount of alum needed for the volume of water in your tank. The correct dosage depends on the water's turbidity and quality.
- Add the measured alum directly into the water tank.
- Stir the water to dissolve the alum thoroughly. This is a critical step to ensure the alum is evenly distributed and can effectively interact with the impurities in the water. You can use a long rod or paddle for larger tanks, or circulate the water if possible.
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Allowing Settling
- Once the alum is completely dissolved and mixed, stop stirring the water.
- Allow the water to sit undisturbed for a minimum of 1 to 2 hours, but ideally for a longer period, such as overnight.
- During this resting period, the dissolved alum forms 'flocs' – larger clumps of impurities.
- These flocs become heavy and settle to the bottom of the tank, leaving clearer water above.
Why Use Alum in Water?
Alum is commonly used in water treatment as a coagulant. Its primary function is to remove turbidity, color, and other suspended solids that make water appear cloudy or dirty.
- Flocculation: Alum neutralizes the negative charge on suspended particles, causing them to stick together and form larger, heavier flocs.
- Sedimentation: These flocs then settle to the bottom of the tank due to gravity.
- Improved Clarity: The water left at the top becomes significantly clearer and less turbid.
Settling Time Considerations
As the reference states, the settling time is crucial for the process.
| Settling Time | Outcome | Notes |
|---|---|---|
| Minimum 1-2 hours | Sufficient for initial settling | Removes larger particles effectively |
| Ideally Overnight | Allows for maximum settling of finer flocs | Results in clearer water |
Allowing a longer settling time, like overnight, ensures that even smaller particles are captured by the flocs and settle, leading to better clarification of the water.
After the settling period, the clear water can be carefully drawn off from the top of the tank, leaving the settled sediment behind. The sediment at the bottom should be periodically removed and properly disposed of.
