I have a drain in the bottom of mine. I collect and use it on my citrus trees and other plants. I try to do it every day. If I let it go, I have a sump pump and again, pump it to the trees.

You might try to siphon the solids into a bucket...let it sit for awhile, then collect/ re-use the cleaner water from the top. The solids...If you don't have any veggies (in the ground) or fruit/citrus trees, maybe you can give/trade it to someone who could use it ?