Correct Answer - Option 3 : Only c and d
Explanation:
Conventional methods of water treatment ( Sedimentation, filtration ) don't materially change the mineral content of water. So, various methods are used to reduce the salinity of the water.
1) Freezing :
- Water is transposed from saline water to the solid phase as ice. The ice crystals formed constitute essentially pure water.
2) Reverse osmosis :
- A membrane permeation process for separating relatively pure water from a less pure solution.
- For this saline water is passed through a semi-permeable membrane under pressure
3) Electrolysis :
- Unaided osmosis is a slow process hence it is combined with electrolysis.
- Application of an external electromotive force can draw the ions away from the salt solution and towards the electrodes to remove the salt of the solution.
Note: Alum coagulation, flocculation comes under sedimentation and carbon filtration is a technique used for filtration of water, and as discussed above, sedimentation and filtration are not enough for removing salts from the water.
