Backflush system in operation at a plant in Canada. This video shows the backflush in an activated sludge tank for a pulp mill. The system is being flushed using the airlift principle, which involves reversing the flow from the digestor through the jet nozzles, and out at the top of the tank. A strainer can be used to collect these solids, if necessary.
We have an animation video of this process: https://youtu.be/z-wzZFixq4Q