Energy conservation opportunities in municipal water and wastewater systems

Municipal water and wastewater systems are heavy users of energy, not only directly through the use of electricity, natural gas, and other fuels but indirectly through the use of large quantities of chemicals produced by energy-intensive manufacturing processes. A recent study by the US Office of Water Research and Technology showed water and wastewater systems to be the largest single component of energy consumption by local units of government, averaging about 25 percent of the total municipal energy use.1 Moreover, recent utility rate studies have shown that the direct energy costs of water and wastewater systems account for fully 20 percent of their total operating budgets.2 In 1979 the energy administration of the Michigan Department of Commerce sponsored a study to identify ways in which energy could be conserved in existing water and wastewater facilities. The objective of the study was to identify cost-effective energy conservation measures that could be implemented statewide at Michigan's 1100 municipal plants. These systems account for 2 percent of all electricity and 0.5 percent of all natural gas consumed in the state.3 The consulting firm of Ayres, Lewis, Norris & May, Inc., of Ann Arbor, Mich., was retained to perform this study. The study methodology consisted of three phases: energy audits to identify energy conservation opportunities (ECOs) at four study sites; analysis of the ECOs for cost-effectiveness; and extrapolation of the results to identify the potential for statewide energy savings in water and wastewater facilities.