More Energy, Less Biosolids
February 1, 2016
Paul Wood, P.E., Lockwood, Andrews & Newnam Inc.
Energy use can account for as much as 10 percent of a local government’s annual operating budget, according to the U.S. Department of Energy.¹ A significant amount of this municipal energy use comes from wastewater treatment facilities. According to estimates by the New York State Energy Research and Development Authority, electricity typically accounts for 25 to 40 percent of the operating budget for a wastewater utility.
Most plants treat wastewater by screening the flow, removing grit and removing settable solids in large quiescent basins known as primary clarifiers. The settable solids account for approximately 35 percent of the organics entering a plant. The other 65 percent of the organics must be treated further so that the water is suitable for discharge. This process is normally performed in a secondary treatment system with an aeration basin in which bacteria are grown. With the addition of oxygen from air that is bubbled into the water, the bacteria multiply by consuming the organics as their food source and give off carbon dioxide like all other non-plant life.