Where does the water go after it goes down the drain?
It depends. In most US cities, sewers are gathered in larger pipes, called collectors. These, eventually reach what is called a waste water processing plant. These facilities, usually operated by specialized municipal services, basically treat the water so that it may become as close to natural water flowing in the rivers as possible. Generally, waste water treatment comprises several so called steps: first, the so called mechanical step, includes large pools, were water settles and leaves mechanical impurities (mud, detritus, household wastes, etc.). The mud colected here is usually composted and sterilized and then it is generally used as landfil. The water collected from above it, goes to the second step, which is usually a biological step, containing of special bacterias or water plants (such as the water hyacinth, certain types of algae, etc.) are used to elliminate organic matters dissolved in the water as well as some metals such as cobalt, lead, copper, etc. The last phase is t
