You can buy a holding tank that you can dump into and haul away fairly easily. You might want to invest in a Macerator with pump so you can pump up into it while it is in your truck bed, then just gravity drain to empty at the dump site. I think Camping World has the Macerator and holding tank that you can check out. This would be the easiest way, but I'm sure there might be cheaper ways others have come up with that work.
I like easy, reliable, and quick as there are enough honest headaches no matter what we do lol