The sequencing batch reactor (SBR) at Culver, Indiana, has two 440(sup 3) aeration basins that have received primary effluent on an alternating, fill-and-draw basis since May 1980. During normal SBR operation, liquid level variation and mixed liquor suspended solids (MLSS) concentrations are identical in both aeration basins. In a special study conducted during June and July 1984, both liquid and MLSS levels were changed in each aeration basin. Both basins were operated with control strategies that resulted in biological phosphorus removal. Sludge wasting and energy use was monitored closely for both loading conditions. When energy use was corrected to include only BOD(sub 5) that was fully oxidized and not removed with the waste sludge, energy use in the two systems was essentially the same.