How does sewage become natural water, and how does domestic sewage become tap water?

Precipitation first: Alum can be added (activated carbon seems to work as well, but I feel that the water is getting dirtier and dirtier when I look at it) to speed up - dispose of the relatively large water-insoluble particles.

Refiltration: Use filter paper or other filtration devices to dispose of the small insoluble particles that have not been disposed of, and generally do it several times.

Final distillation: Dispose of the few remaining water-insoluble particles and water-soluble substances (usually water-soluble inorganic salts).

But if the impurity is liquid, you have to check its boiling point: if it is lower than water, you should control the temperature near its boiling point, do not reach the boiling point of water, and evaporate this substance first (for example, alcohol, you control the temperature at 80 degrees, and see that there is no obvious steam coming out, you can increase the temperature to boil water); If its boiling point is higher than that of water, then control the temperature around 100 degrees and do not reach the boiling point of that substance, so that the water is collected. (If this happens, you just need to put the jar with the sewage in a pot of boiling water - you are not afraid to heat it, but the bottom of the jar should not touch the bottom of the pot - so that the temperature can be kept at 100 degrees and will not change, unless the water in the pot is dry or the bottom of the jar touches the bottom of the pot).

To deal with liquid impurities, it is generally treated by chemical methods, generally by adding a substance to form a water-insoluble solid with impurities.

Be more careful when encountering toxic liquid vapors (especially most organic solvents); Substances that pollute the atmosphere (or anything else) must be collected and disposed of with appropriate chemical methods.

You can also distill directly, and the distilled water should be very clean, except for some microorganisms that are not killed during the heating process, there should be no impurities.

Therefore, the water plant should also add sterilization agents.

Have you ever seen those water dispenser filters?

With a strainer, stone, charcoal, sponge. and other materials are stacked into several filter layers.

I guess it's like this. Filter.

Stone. Sponge.

Charcoal. Sponge. Stone. Sponge.

Charcoal. The water that comes out should be the same as the clear water...

It should be filtration, and now it seems that there is a kind of machine that turns sewage into drinkability.

Even if domestic sewage is treated, it can only be called "reclaimed water" and cannot be used as drinking water.

The water cycle processes in nature are:

It rains on the ground and seeps into the soil, forming groundwater; It flows on the surface of the earth and forms an above-ground river;

Groundwater rises to the sky through the evaporation of plants to form water vapor, and then falls back to the ground in the form of rain and snow when it is cold.

The water of the rivers eventually flows into the sea, where it evaporates to form clouds, and when it rains, the water in the clouds returns to the ground.

The reservoir is just a man-made reservoir, but it's bigger.

"Tap water" is compared to the need to dig wells to lift water. The tap water comes from the "waterworks". The water from the waterworks comes from the surface water of rivers and reservoirs or the extracted groundwater, which is precipitated and disinfected and then piped to thousands of households to become clean drinking water.

After use, the reclaimed water must also be discharged by the river or purified by the soil, and finally purified according to the above process, and re-added to the water cycle for people's use.