How long would you allow an activated sludge process to react and stabilize after a change?

1 week

Explanation:

Only one process change should be conducted each time to provide the system enough time to react to the change and stabilize before making another change. One week is the usual amount of time the plant should have to react and stabilize after a process change has been done. Although experience may provide enough knowledge to ascertain the results of a process change within a few days, waiting a whole week is recommendable at first.