The availability of clean and reliable sources of water is a critical issue across the United States and throughout the world. The Innovations for Existing Plants (IEP) Program’s Water-Energy Interface is focused on developing an understanding of the impacts of electricity production on water quantity and quality and on research, development, and demonstration of technologies to minimize any negative impacts.

“Thermoelectric Power Generation” is a broad category of power plants consisting of coal, nuclear, oil, natural gas, and the steam portion of gas-fired combined cycles. Thermoelectric generation represents the largest segment of U.S. electricity production, with coal-based power plants alone generating about half of the nation’s electric supply. Each kilowatt-hour (kWh) of thermoelectric generation requires the withdrawal of approximately 25 gallons of water (weighted-average for all thermoelectric power generation), which is primarily used for cooling purposes. Other power plant water uses include water for operation of pollution control devices such as flue gas desulfurization (FGD) technology as well as for ash handling, wastewater treatment, and wash water. According to United States Geological Survey (USGS) water use survey data, thermoelectric generation accounted for 39% (136 billion gallons per day (BGD)) of all freshwater withdrawals in the nation in 2000, which is second only to irrigation. The following figure illustrates the percentage of total U.S. freshwater withdrawals by source category for 2000.

Source: United States Geological Survey. Estimated Use of Water in the United States in 2000.

It is important to distinguish between water withdrawal and water consumption. Water withdrawal represents the total water taken from a source while water consumption represents the amount of that water withdrawal that is not returned to the source, generally lost to evaporation. USGS freshwater consumption data for the year 1995 (the most recent year for which this data is available) is presented in the figure below. Freshwater consumption for thermoelectric uses appears low when compared to other use categories. However, even at 3% consumption, over 3 BGD were consumed. It is expected that the quantity of freshwater consumed by thermoelectric generation is higher today than in 1995, with DOE/NETL estimates of 6.2 BGD consumed by thermoelectric plants in 2005.

Source: United States Geological Survey. Estimated Use of Water in the United States in 1995.

In addition to the significant amount of water needed for the generation of electricity, power plants may also impact water quality. Both the Clean Water Act (CWA) and the Safe Drinking Water Act (SDWA) regulate the discharge of pollutants from power plants to receiving waters as well as the intake of water for cooling and other power plant needs. For instance, the CWA contains Sections 316(a) and 316(b) which cover water thermal discharge and cooling water intake structures. Of additional concern is the deposition of trace quantities of air pollutants into water systems.

In response to the growing recognition of the inter-dependence between freshwater availability and quality and electricity production, the IEP Program is funding research directed at coal-fired power plant related water management issues with the overall goal of reducing the amount of freshwater needed for power plant operations and minimizing potential impacts on water quality. Research encompasses laboratory and bench-scale activities through pilot- and full-scale demonstrations and is performed in partnership and collaboration with industry, academia, technology developers, and other government organizations. The program is built around the following four specific areas of research. Please click on each research area for additional information.

Non-Traditional Sources of Process and Cooling Water
Research and analysis are being conducted to evaluate and develop cost-effective approaches to using non-traditional (aka alternative or impaired) sources of water to supplement or replace freshwater for cooling and other power plant needs. Examples of non-traditional waters include surface and underground mine pool water, geological carbon sequestration and coal-bed methane produced waters, and industrial and/or municipal wastewater.

Innovative Water Reuse and Recovery
Research is currently underway to develop advanced technologies to reuse power plant cooling water and associated waste heat and investigate methods to recover water from coal and power plant flue gas. Such advances have the potential to reduce fossil fuel power plant water withdrawal and consumption.

Advanced Cooling Technology
This component of the program is focused on research to develop technologies that improve performance and reduce costs associated with wet cooling, dry cooling, and hybrid cooling technologies. In addition, the research area covers innovative methods to control bio-fouling of cooling water intake structures as well as advances in intake structure systems.

Advanced Water Treatment and Detection Technology
Future controls on the emission of mercury and possibly other trace elements have raised concerns about the ultimate fate of these contaminants once they are removed from power plant combustion flue gas. Preventing these “air pollutants” from being transferred to surface or ground waters will be critical. In addition, ammonia from selective catalytic reduction systems used to control nitrogen oxide emissions can appear in a power plant’s wastewater streams. Research is needed for advanced technologies to detect and remove mercury, arsenic, selenium and other components from the aqueous streams of coal-based power plants should effluent standards be tightened in the future.