This is anaerobic sludge being mixed in a circular tank, using an eddy jet mixer. Eddy mixers are typically used in sludge storage tanks and anaerobic digestors. Usually, eddy mixers are used in systems with liquid levels between 5 and 30 feet.
This aerobic digestor in Ohio is being mixed during start-up with clean water. Currently only the pump is in operation, showing the mixing action of the recirculation pump and the jet mixer with no aeration.