Learning about Water Treatment at Home

In the Water Box, we treat water through filtration. Wondering what packs 5 and 6 in your box is for? Read on!

In this activity, we try out the first step in water treatment at home - coagulation through chemical processing.


What you need

1. 2 small glass cups

2. Rice water

3. Spoon

4. Disposable chopstick

5. Water

6. Baking Soda 

7. Potassium Alum

Step by Step

1. Fill one quarter of both glass cups with rice water. One is the control experiment.

2. Add 5 teaspoons of Potassium Alum into one cup and stir well. 

3. Add 3 teaspoons of baking soda into the solution and stir gently to mix well. 

4. Set both cups aside and let it sit for 1 to 2 hours. 

5. Observe what happens to the water in both glasses. What do you notice? The rice water  in the cup with the potassium alum and baking soda solution has turned clear and a white substance has formed on the bottom of the cup.

*Increase the portion of Potassium Alum and Baking Soda if you do not notice the white substance. This activity also works with paint colour dissolved in water. 


The water treatment process in most countries has six steps. They are coagulation/flocculation, sedimentation, filtration, stabilization, fluoridation, and chlorination.

Alum is added to the water coming into the purification process in the first stage - coagulation/flocculation. Alum, when added to raw water reacts with the particles present in water to form a semi-solid substance. This substance attracts other fine particles and suspended material in raw water, and settles down at the bottom. 

In the other stages of water treatment, different chemicals are added to destroy dangerous bacteria, help prevent cavities in teeth and help keep water pipes corrosion free.