how is any cities water safe it comes from a river or lake and then the used water, sewerage goes back there?

Question

when water is in a river, lake or water source a city gets there water from is cleaned it goes through all of the processes and then in to homes used water goes through pipes to a cleaning plant then back into the river so how is it clean

if you add the fact about water getting evaporated then it rains back down how can you say that water isnt contaminated.

chlorine cant get rid of 100% of everything that is in water, but question what gets rid of the chlorine

im not talking about drinking water, im talking about using the water to cook, wash,etc.

Answer 1

First you must define your terms: By contaminants do you mean ALL contaminants or only harmful ones? All processed drinking water comes from sources that contain both kinds of contaminants; harmful and benign. Drinking water is filtered using a column type system with progressively smaller layers of sand and rock. It is then treated with anti-bacterial chemicals and fluorine, and sent to its subscribers. Is this water still contaminated? To be sure it is, but those remaining contaminates are, for the most part, benign. The fact the people aren't flooding hospitals with cholera and dysentery should be proof of that. And all government operated water processing plants check their water several times daily for harmful contaminants, including too much chlorine and fluorine.

Even the water people are paying 1 or 2 bucks a bottle for contains contaminants.

The only chemically pure water is that which has, as a minimum, been double distilled and double deionized, or has been processed through a reverse osmosis filter, and further distilled.

If you're really concerned about drinking only pure water, you could buy yourself a reverse osmosis system and a deionizing column and process your own water. it shouldn't cost more than 6 or 7 thousand dollars.

Answer 2

"Free-range" water may contain any number of things floating or dissolved in it ("You drink that?! Do you know what fish are doing in that all the time?! Stick to whiskey.") That's why cities routinely run the water from wherever they get it through water-cleaning plants which both filter and (hopefully) sterilize it; usually by using chlorine. After the water is used, it is generally (and hopefully) run through a water-cleaning plant again to clear out the worst of the contaminants before it's released back into the wild. It obviously doesn't always work that way, which is why typhus and cholera can be significant problems.

Answer 3

"goes through pipes to a cleaning plant" I think you answered your own question on that point - the cleaning plant removes the contaminants. Furthermore, travel through the soil as ground water also can clean it.

As for evaporation - when it evaporates only the water becomes airborn, and subsequently forms clouds and rain. Existing contaminants are left behind. Of course, new contaminants can be picked up from the atmosphere but that is another issue.