" Will the ingredients used in winemaking, especially the sanitizer affect
the Septic system? Should I use a
different way of disposing of sanitizer water?"

Depends on volume. If it's a single 5-gallon carboy with some Iodophor OK.
But if you are filling 30 gallon trash cans with Chlorox solution to soak
off bottle labels this volume won't help your system. I don't put any
winemaking or beer making waters thru. the septic system...I pump to the
outside using a sump pump.

Bill Frazier
Olathe, Kansas USA