By Vanessa M. Leiby
Providing safe drinking water and reliable wastewater services is a highly energy-intensive activity in North America with estimates of $4 billion spent annually in the U.S. for energy in the water sector. The Environmental Protection Agency (EPA) reports that 3 percent of U.S. national energy consumption, equivalent to approximately 56 billion kilowatt hours (kWh), is used for drinking water and wastewater services. This is the equivalent of approximately 44.8 million tons of greenhouse gas released to the atmosphere each year. Further, drinking water and wastewater services consume 7 percent of the worldwide energy resources. In the U.S.:
- Water utility energy use varies widely from 0.25 to 3.5 kWh per 1,000 gallons of drinking water produced and delivered.
- The median 50 percent of water utilities serving populations >10,000 had electricity use between 1.0 and 2.5 kWh per 1,000 gallons.
- Eighty to 90 percent of water treatment plant energy consumption goes to pumping - raw water, high service, backwash, and distribution system boosters.
- Drinking water and wastewater treatment consume 30 to 60 percent of energy used by municipalities.
These energy costs are increasing as a result of: (1) utilities installing new technologies to meet more stringent and increasing drinking water standards; (2) drought and climate change impacts necessitating treatment of water from lower quality sources and using more energy-consuming technologies like membranes and desalination; (3) aging infrastructure that adds to increased energy consumption through water losses and inefficient mechanical systems such as pumps and motors; (4) growth and system expansion that have dictated utilities transport water to greater distances and greater system elevations; and (5) installation of new generating plants and transmission lines and demands for high-quality power.
This has led some utilities to develop aggressive energy management strategies to improve energy efficiency and reduce energy consumption and costs. Energy efficiency is the use of less energy to provide the same level of service and water quality. The California Energy Commission (CEC) estimates that water system energy savings of 15 to 30 percent are "readily achievable." These savings can be realized through utilizing new, energy-efficient technologies; incorporating energy-efficient practices; and taking advantage of incentives and rebates.
Through application of energy management strategies and practices, energy costs can be controlled. There are substantial opportunities and potential to reduce energy costs, some of which can be implemented easily with a limited investment cost, such as taking advantage of systems upgrades or expansion to incorporate efficient processes and technologies. Monetary benefits are commonly at the forefront of any system improvement. However, reducing energy consumption not only reduces energy costs and operating expenditures but has a direct impact on reducing greenhouse gas emissions. Additionally, the improvements lead to improved system efficiency and process control.
Utilities that are interested in learning more about energy efficiency for drinking water systems might want to obtain a copy of a Water Research Foundation report [Project #4223] co-funded by the New York State Energy Research and Development Authority (NYSERDA) titled Energy Efficiency Best Practices for North American Drinking Water Utilities that was published in late 2011. The report contains a number of resources for further information and a searchable database of best practices as well as a roadmap and case studies of energy-efficiency practices. The report can be accessed at http://www.waterrf.org/Pages/Projects.aspx?PID=4223.
About the Author: Vanessa M. Leiby is the executive director of the Water and Wastewater Equipment Manufacturers Association (WWEMA). She was also the principal investigator for Water Research Project #4223 mentioned above.
