The paper discusses how current practices for aeration system design for domestic wastewater facilities that can lead to oversized blowers. Oversized aeration blowers limit operational flexibility and prevent the optimization of power use. The conservative assumptions made by design engineers, facility owners, and state agencies during the design process often result in blowers whose capacity far exceeds that needed for nearly all operating conditions over the lifespan of the blowers. Too much air, or lack of ability to control air, is one of the most common problems in biological nutrient removal (BNR) processes. Consistently providing too much process air not only wastes power and increases operating cost, but it can compromise performance by increasing effluent concentrations of phosphorus, nitrogen and suspended solids. Aeration of activated sludge accounts for 40 to 60% of a conventional wastewater plant's total power requirements. To minimize energy costs in their facilities, owners need blowers and aeration systems that are able to supply just as much air as needed by the biological treatment process.