YOU DON'T CREATE HAZARDOUS WASTE
The detergent and water solution should never require disposal:
(1) The floating oils cascade over an interior weir plate and into the side pocket.
(2) After the oils are removed, use the upper drain valve to capture and save all the water above the sludge line.
(3) With the sludge removed, pour the original water content back into the tank.
(4) Everyday you add fresh water equivalent to 20% of the tank volume as
needed to compensate for evaporation. This process constantly refreshes the solution.