Do not dump this stuff into the sewer, down the sink, or in the toilet!!
The auto parts store where you buy the replacement, your Mercedes dealer (if you bought it there), or a branch of your local government can either accept it, or direct you to a recycling center.
The base material of antifreeze is Ethylene Glycol, and is so toxic that it is rated as a poison. It is also sweet, so animals are attracted to it, and will drink it if it is left out. They will soon die afterwards. Do not leave it out in the open, do not allow your own pets or kids anywhere near it, and do not take this matter lightly...
Here's a quote from a Popular Mechanics article on flushing your cooling system:
"If your car has a copper radiator or heater core, the coolant is contaminated with lead solder. Many municipalities have hazardous-waste disposal facilities that will take it. Also, in most of the United States it's illegal for professional mechanics to dispose of used coolant, so you may be able to take it to the local shop and ask if they'll handle it."
So, as you can see, there's more contaminants to worry about besides the EG, there's also lead.