Hello All! Interesting question. I have been doing the country living thing for many years now, (going on 32 years actually). Way back when, my water softener installer asked if I wanted the brine solution emptied into my septic or into the yard. At first I was leaning towards the yard, however he produced some documents that indicated through studies that salt in the septic tank actually creates an environment that the bacteria thrive and bloom in. Being as a septic system works on bacteria, I chose to empty the brine directly into my septic tank. (Looking at the brine solution in my softener, it appears to be much more saline than marine aquarium water). I pump the septic tank out as a matter of routine maintenance every 7 years. I have never experienced significant sludge in either chamber, never had a plugged baffle and never had a weeping tile blockage. I am actually considered stretching my maintenance schedule out further, maybe every 10 years. Anyway, from my experience nothing detrimental has happened to my system from draining my softener salt into the septic tank. I am a fan of saltwater into the septic and would recommend it! My 2 cents for what ever it is worth!
Take care
Dave