The invention is directed to controlling wastewater treatment system operations in response to a demand associated with the influent conditions. Fluctuations or variations in flow and/or concentration characteristics of the liquid to be treated can create the reduce the operating demand and the treatment system can be operated to a reduced or standby operating mode by adjusting the operation of one or more unit operations or subsystems in response to such variations. The wastewater system can also be operated to treat an anticipated wastewater stream based on the historical characteristics of the stream.