In order to make sure that supplies of drinking water are clean water treatment plants are operated. In general, water supplied to our homes must be attractive looking ( colourless), odourless and safe to drink. In order to achieve this, there are a number of steps involved in the treatment of water.
- Screening:- The water passes through a wire mesh to remove any floating debris like twigs and plastic bags etc.
- Settling:- The water flows into large tanks called settling tanks or sedimentation tanks. In these tanks aluminium sulphate (commonly called "Alum") is added to the water. In other words, the aluminium sulphate takes the cloudiness out of the water and leaves the water clear.
- Filtration:- The water is passed through filtration beds. These consist of layers of sand and gravel. Filtration beds ensure that even the smallest particles of dirt are removed from the water.
- Chlorinating:- The next stage in the treatment of water is to kill germs which are left in it. Small quantities of chlorine are added to the water to kill bacteria. The chlorine is not present in large enough quantities to smell or taste it.