'If your city uses a sewage treatment facility for effluent, straight
down the drain is fine.'
If you do a little research, you will find no mention, anywhere, that
this practice is 'fine,' but you will find, just about everywhere you
look, just the opposite......do not dump antifreeze down the drain!
Funny that this comes up every so often.
This is just a little tidbit from the MSDS :
ECOTOXICITY
The toxicity of this material to aquatic organisms has not been
evaluated. Consequently, this material should be kept out of sewage
and drainage systems and all bodies of water.
Here is a sample MSDS :
http://www.havoline.com/images/products/pdfs/anti_exlife.pdf

Happy reading..........

Gracias,
                    Miguel