Have you ever thought about where the water from the tap originates? Or where the wastewater that goes down the drain goes? The answer is that water comes from rivers, lakes, and underground supplies called aquifers. After providing the appropriate level of treatment and disinfection, the water is pumped, under pressure, through a series of water mains and pipes that deliver the water to our homes. Importantly, this same water supply provides the water required to provide fire protection for our communities. This dual use requires that the water be delivered at pressures that usually range from 40 to 60 psi. The pumps used to develop and maintain this pressure require electric energy to supply the motors and pumps with energy.

After we use the water, it flows by gravity through another series of pipelines. These pipes slope downward, using gravity to provide the energy needed by the water to flow. When the pipelines get deep enough, a lift station is needed to raise the water. Eventually the wastewater flows to a facility that removes the solids, organics, nutrients, and other material, so that clean water can be discharged to the local “surface” water. Large amounts of electric energy are used in the process of lifting and cleaning the water. 

Energy conservation is the most cost efficient method of improving the energy efficiency of a water or wastewater facility. Also important is the use of renewable sources of energy. Solar energy in particular, has been readily adopted by the water and wastewater community. There is renewed interest in the use of digester gas as a fuel to generate electricity and heat. Wind, geothermal, and hydroelectric all provide interesting options for some facilities. The use of biomass as an alternative source of heat for sludge drying may be a cost-efficient alternative. My prediction is that someday these facilities which are significant energy users will one day become net energy producers.

Pete Cavagnaro
Johnson Controls, Inc.