You should NEVER put Bentonite down ANY pipes that lead to a septic tank - Bentonite will ruin a septic tank.
Even if you don't have a septic tank, I wouldn't recommend putting 10k down the tub OR the toilet - it's one thing to allow a cup or two mixed into a full bathtub of water 'down the drain' and then follow that with the water from all the daily bathing and showering...but you're talking enough Bentonite to totally clog a system.
I'd dispose of it any way but through the plumbing & pipes...and that's absolutely the case if you have a septic tank.