Samuel Chiltern answered
There are two ways in which the sun can be used to purify water. One method uses evaporation and condensation to remove polluting chemicals, and the other approach uses ultraviolet (UV) rays to kill bacteria, viruses and parasites.
Solar Stills, and Using Evaporation to Purify Water
Solar stills have been used to clean water using the sun's energy since at least the 19th Century.
The basic principle relies upon using the sun's energy to evaporate the water, thereby turning it into vapour. This vapour is then trapped and encouraged to re-condense, at which point it is collected as purified water.
The beauty of this approach is that, by evaporating water, all the pollutants in the water (such as salt or acids) are left behind when the water turns to vapour. When that vapour re-condenses, the water that is collected in a separate container is now clean.
This technology has no carbon cost, since it relies entirely upon the heat energy from the sun to work. Being able to build a solar still is an important survival skill, and the technology also comes in handy in areas where there is no running water.
Using The Sun's UV Rays to Kill Bacteria
Sunlight is a powerful source of UV light. With enough exposure, UV light is dangerous to all living creatures, because it damages cells. This is why you shouldn't spend too long out in the sun without having applied sun protection.
Smaller, simpler organisms such as bacteria are much more easily damaged by UV rays, because they don't have many cells, so sustaining damage to just a few of those can be fatal. The light energy disrupts the chemical bonds between the atoms of DNA in the organism.
If the exposure is sufficient, the damage will kill all the micro-organisms in the water, sanitising it in the process.
Solar Stills, and Using Evaporation to Purify Water
Solar stills have been used to clean water using the sun's energy since at least the 19th Century.
The basic principle relies upon using the sun's energy to evaporate the water, thereby turning it into vapour. This vapour is then trapped and encouraged to re-condense, at which point it is collected as purified water.
The beauty of this approach is that, by evaporating water, all the pollutants in the water (such as salt or acids) are left behind when the water turns to vapour. When that vapour re-condenses, the water that is collected in a separate container is now clean.
This technology has no carbon cost, since it relies entirely upon the heat energy from the sun to work. Being able to build a solar still is an important survival skill, and the technology also comes in handy in areas where there is no running water.
Using The Sun's UV Rays to Kill Bacteria
Sunlight is a powerful source of UV light. With enough exposure, UV light is dangerous to all living creatures, because it damages cells. This is why you shouldn't spend too long out in the sun without having applied sun protection.
Smaller, simpler organisms such as bacteria are much more easily damaged by UV rays, because they don't have many cells, so sustaining damage to just a few of those can be fatal. The light energy disrupts the chemical bonds between the atoms of DNA in the organism.
If the exposure is sufficient, the damage will kill all the micro-organisms in the water, sanitising it in the process.
