Stormwater is often thought of as a burden. Too much of it can overwhelm wastewater treatment facilities, flood communities, and lead to the pollution of lakes and rivers. There is debate on who’s in charge of it and how it should be managed. Several communities have invested millions, and some even billions, trying to control stormwater. Even chicken farmers have issues with stormwater.
But a group of electric utility researchers think stormwater may have more positive potential.
Bob Goldstein and his team at the Electric Power Research Institute (EPRI) are investigating the possibility of using stormwater runoff to the meet the large water demands of power plants.
“The pressure is on the electric power sector to reduce its use of freshwater,” said Goldstein, a senior technical executive of water and ecosystems at EPRI. “The power industry needs to create strategies and technologies that are effective in reducing water and still cost efficient.”
Production of electrical power is one of largest uses of water in the United States. Thermoelectric power withdrawals accounted for 49 percent of total water use, according to the U.S. Department of the Interior. Most of the water is used for cooling purposes.
Fortunately, power plants do reuse most of the water they remove from the environment. Because of this the total water consumption for power plants is only approximately 4 percent of total water withdraw in the U.S. But that smaller consumption requirement doesn’t mean power plants are immune to water scarcity.
“Although they are not consuming as much water, they need a lot of water up front in order to function,” explained Goldstein. “So if they are in an area where the water supply is restricted because of drought or other reasons, they need to have a strategy to conserve freshwater.”
EPRI conducted two studies on the potential for stormwater use at power plants. The first, Evaluation of Stormwater as a Resource for Power Plant Cooling, investigated the “potential to use stormwater runoff in lieu of withdrawals from a freshwater body to meet water needs of different power plant processes.” The second study “The Potential for Using Stormwater in Power Plants: Lessons Learned from Case Studies at Two Great River Energy Plants,” took a more focused approach, analyzing stormwater use at two power plants: Elk River Energy Recovery Station in Minnesota and Coal Creek Generating Station in North Dakota. It also considered generating stations with water demands similar to those of Coal Creek but placed in other climatic conditions (representing Upstate New York, Illinois, and Southern California).
Two sources of stormwater were discussed and evaluated in both studies — onsite and offsite. Onsite stormwater runoff, after being collected from the power plant’s property and placed in sediment basins, typically can be used without treatment in flue gas desulfurization systems (which remove sulfur from exhaust gases before releasing them), in ash systems and cooling towers in coal-fired plants, and in cooling towers in combined-cycle, oil/gas and nuclear plants.
Offsite stormwater, which usually is easier to procure in larger quantities, can provide a significant volume of water for power plants. There is potential for offsite stormwater to supply over half of the water requirements for some plants. However, the water must be evaluated carefully, because offsite stormwater is more likely to have come into contact with substances they make it unsuitable for use without some form of treatment. Transportation must also be considered when using offsite stormwater. If it has to be transported a great distance, the cost could outweigh the benefit, said Goldstein.
Ownership is also an issue. “There is always this legal question about who owns the stormwater, especially when it’s not on your property.” Goldstein explained. “Is it there for anyone to harvest? That is an open-ended question that has never been answered.”
Despite these potential issues, stormwater is still a viable option for reducing freshwater use at power plants, Goldstein said.
“Stormwater use at power plants is something really worth considering,” he said. “As population continues to grow, I think the demand for alternative water resources will continue to increase. There is pressure across our entire society to manage water more carefully and reduce overall withdraw use. This could be a way to do it.”
Image credit: "Power Plant," © 2010 FromSandToGlass, used under an Attribution 2.0 Generic license: http://creativecommons.org/licenses/by/2.0/deed.en