Method for treating wastewater, in particular municipal wastewater, in which the wastewater is initially received in an equalization basin reactor for performing an infiltration and inflow equalization process. The equalization basin reactor has sufficient capacity for the increased inflow of wastewater received under wet weather conditions. However, the increased inflow is not merely stored in the equalization basin reactor for later processing, but the wastewater treatment process continues throughout the wet weather period with the first stage wastewater treatment being performed in the equalization basin reactor, which further provides a substantially constant outflow of partially treated wastewater for subsequent treatment stages.