Brine discharge can be pretty bad for the environment, so we do some tank exchange thing with Culligan. Every other week they install a new tank and remove the old one to be recharged. Working great so far.
It's about $50 a month. Nothing gets released at my house, which is nice. I'm a little out of my depth with the chemical reaction, but the idea is inside the tank are a bunch of resin beads impregnated with stuff calcium and magnesium ions will bind to. So as water flows through the tank the calcium and magnesium is removed and stored in the beads. So the beads store it, but can't store an infinite amount. The tank gets switched out every 2 weeks and culligan takes the old tank back and reverse the process. I'm sure this involves nasty stuff, but hopefully economy of scale and regulations make it a cleaner process than just dumping the salt in the ground.