Quite a fancy set up!
I usually put a plastic chair in the shade surrounded by three plastic
garbage cans of water plus a 5 gallon bucket with a cup of Clorox. Use
one garbage can for the first rinse, next one for second rinse, then a
brief Clorox dip, then a final rinse in the 3rd garbage can, and spread
them out on old window screens in the shade to dry.
I haven't had a lot of donations to give to our club sales recently -
mostly just growing seedlings - but back in the day, that was usually
washing to get a few hundred rhizomes quite clean.
Fortunately, my soil is organic gravelly loam, so other than bits of
sand or small rocks and a fine layer of soil, most soil just shakes off
and a quick swish thru a bucket of water gets them pretty clean. Water
that sloshes on the ground disappears fast on my gravelly creek soil. &
it's usually hot enough at digging time that the spring water feels good
to play in.
Wouldn't work for clay.