From Water Utilities Set Their Sight on Energy Savings - link:
"Pumping and aeration systems are the highest energy users in a water treatment plant. Typically aeration systems are responsible for 50 to 60 percent of total wastewater treatment plant energy use. In some areas, pumping within a water distribution system can use as much as 80 percent of total energy for municipal water supply. As a result, systems not tuned or unable to reduce excess aeration blower or pump capacity can waste energy and money for decades. This waste can also result in greater greenhouse gas emissions over the life of the plant."