Water is one of the world’s most precious resources, but relatively little of it is drinkable without treatment. Prior to treatment, it can contain sediment, pathogens, and chemicals that need to be removed before it is safe to drink. The process is surprisingly simple, and it relies on just a few broad steps.
The first step is the removal of sediment and other particles from the water. Most of them have a negative charge, so the treatment workers expose the water to chemicals with a positive charge. The two react and bind together, which turns the small particles into heavy clumps. They are heavy enough that they will settle at the bottom of the tank on their own, given just a little bit of time.
That process gets rid of most of the sediment, but there are other things in the water. Some particles will remain, and there will still be bacteria and other microbes in it. Filtration exists to solve that problem.
The water gets pumped through a series of filters, each of which has holes of various sizes. Water molecules are small, so they can pass through the holes, but most of the particles and pathogens will be too large to get through. They will get stuck on the filters, which can be cleaned or replaced to get all of the waste out of the system.
The last step of the standard treatment process purges the last remnants of bacteria from the water. Antimicrobial chemicals, usually a small amount of chlorine, are added to the water to get rid of any pathogens that made it through the filters. It will remain int he water to protect it from any bacteria or other microbes that are in the pipes that take it to homes.
This is also the stage where fluoride is added to the water. The chemical helps to prevent cavities and strengthen teeth. The effect is so large that it has become a standard water additive in order to help prevent oral disease.
Other methods, such as distillation, see occasional use. Desalination is another common option, which relies on similar techniques that are optimized to remove salt from the water. These methods are getting cheaper and demand for water is increasing, so it is likely that they will become more common in the future. Some groups are also looking into new ways to recycle water, which may have benefits beyond simply stretching the water supply in order to support more people. It is hard to say what the future holds, but it is highly likely that it will involve even more improvements to humanity’s water treatment systems.