Where does wastewater go?

When you pull the drain plug or flush the toilet, the wastewater goes down your home's drain pipes.
Those drains are connected to the City's sewer pipes.
Sewer pipes are buried underground, usually under the street.

The sewer pipes empty into larger sewer pipes, called "trunks".
(just like the trunk of a tree, with the smaller pipes being the "branches")
The trunks finally end at one of the City's six (6) wastewater treatment facilities.
Here, the wastewater is cleaned up.

Gravity does the hard work of moving the wastewater.
Sewer pipes are always built with a slope, never flat.

The reason:  water (wastewater, too) flows downhill.
So wastewater from your home flows through underground sewer pipes, all the way to a wastewater treatment facility.
It may have to travel quite a few miles to get there, downhill all the way.