Membrane Purification Process

The membrane water purification process can be seen in the below figure:1. Reservoir
Similar to the conventional purification process, the water is gently mixed by aeration process in the reservoir.

Then, the water is fed to the waterwork through pipe for purification.

2. Screening
Screening trapped large objects to ensure there is no damage done on the membrane that is used to purify the water.

3. Coagulation and flocculation
Chemical substances such as alum and lime are added to the water.

However, in membrane purification process, the amount of the alum that is needed is smaller compared to that in the conventional purification process.

The reason for this difference is while the conventional purification process requires the settling down of the sediment for easy removal, the membrane purification process is able to filter them.

4. Immersed ultra filtration
In this process, water is being sucked out through a semi-permeable membrane (i.e. many tiny holes on the surface of membrane).

Clean water will be sucked into the membrane, leaving behind the impurities. This clean water is then pumped out from the membrane.

In the filtration process, not all the water is subjected to the further purification, as 5% of the water is rejected.

This process is done in membrane tanks. Chestnut Avenue Waterworks in Singapore has 16 membrane tanks, each of them has 5 cassettes, and each cassette consists of 64 modules. Each one of the modules consists of more than 2000 membranes. Therefore each tank will have 640000 membranes. So cool!

This is the picture of the cassette:

5. Re-lift pumping station
In this process the water is pumped to the next station, which is the chlorine contact tank.

6. Chlorine contact tank
Same as the conventional purification process, fluorine and chlorine are added to the water,when it is broght to the chlorine contact tank.

Chlorine plays important role in the purification of water as it acts as disinfectant and it also helps to take care of the water's colour.

7. Clear water tank
Lime is added to the water in the process of going to the clear water tank.

Lime plays a role in the adjustment of pH of the water.

8. To supply network
Ammonia is added also to the water fr the same aim that is mentioned in conventional purification process above.

This purification , unlike the conventional purification, does not require that much space.

It is also able to purify water from lower quality, and thus this purification act as a preparation for the opening of Marina Bay Barrage, which is located at an urban area, and predicted to contain more polluted water.

Moreover, using membrane technology makes Singapore stays advanced in its water purification technology and keeps up with world's development.

However, membranes have shorter lifespan compared to the machines in the conventional purification process, for example the sand in the filter needs to be replenished every ten years, while the membranes have seven years of lifespan.

This purification also need more electricity and the maintenance fee is also higher as it needs more regular maintenance than the conventional way. Thus it has higher operating cost, reaching 30% more than that of conventional purification.