Distillation is probably the oldest method of water purification. Water is first heated to boiling. The water vapor rises to a condenser where cooling water lowers the temperature so the vapor is condensed, collected and stored. Most contaminants remain behind in the liquid phase vessel. However, there can sometimes be what is called carry-overs in the water that is distilled. Organics such as herbicides and pesticides, with boiling points lower than 100 °C cannot be removed efficiently and can actually become concentrated in the product water. Another disadvantage is cost. Distillation requires large amounts of energy and water.
Distilled water can also be very acidic, having a low pH, thus should be contained in glass. Since there is not much left, distilled water is often called “hungry” water. It lacks oxygen and minerals and has a flat taste, which is why it is mostly used in industrial processes.
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