Yeah, this seems like an pretty easy issue to me. Just have the output clamped to the side of your sump, so the level of the hose is well above the water level. It can't back-siphpon out of the sump if it isn't in the water. It is just a tiny bit more noisy this way because the water splashes down into the sump, but my return pump masks that pretty well.

I've been running mine this way since I got it with no problem.