Conventional Purification Process

The conventional water purification process can be seen in the below figure:1. Reservoir
Water from the reservoir are mixed with the imported water from Malaysia. Here, water is mixed by pumping air into the reservoir to create convection currents. The Aeration described above will promote homogeneity and control odour.

The water is then fed to the waterwork for purification process.

2. Coagulation and Flocculation
Chemical substances are added to water in this stage:

a. Lime: used to control the pH of the water.
b. Aluminium sulphate (Alum): cause impurities in the water to clump together as flocs. As the size of flocs becomes larger, it becomes easier for them to be deposited in the next process.
c. Chlorine: act as disinfectant.

3. Sedimentation
The particle that coagulate will settle down in this process.

4. Sand Filtration
An example of a sand filter:

5. Chlorine Contact Tank
Before sending to the chlorine contact tank, fluorine and chlorine are added to the water.

Fluorine helps in the development of strong teeth and bones for children. It is added in under the instruction of Ministry of Health.

6. Clear Water Tank
In the process of going to the clear water tank, lime is added to the water for the pH correction.

7. Supply Network
Before the water is sent to the supply network, ammonia is added to the water.

Ammonia will react with chlorine to become chloramine. Chloramines are weaker disinfectants than chlorine, but are more stable, thus extending disinfectant benefits throughout a water utility's distribution system.

This purification process is done by most reservoirs in Singapore. Conventional purification actually needs a lot of space for the equipment used. In both Bedok and Chestnut Avenue Waterworks, all the processes are clearly segmented. One low-rise structure is designated as the sedimentation station, another one as the chlorine contact tank, and so on. Wow!