World Water Day is fast approaching (March 22nd) and this year's water celebration also serves as a kick-off to the UN's Year of Water Cooperation. While water cooperation might conjure thoughts of governments working together to protect freshwater resources amid myriad disputes and slights, I'd like to highlight the limited but growing cooperation between two unlikely allies: power plants and sewage.
Okay, so "sewage" is a nasty slur for "wastewater." What power plant owners are really interested in is treated wastewater - or wastewater cleaned to a greater or lesser extent - of which treatment plants have plenty.
With about 32 billion gallons of wastewater treated every day across the country, there's a lot of supply available. And, as luck would have it, there's also a lot of demand for that usable wastewater. Power plants account for nearly half of all water withdrawn in the US, an astounding 200 trillion gallons per day, to cool steam used in the process of generating electricity. The thirstiest of all power plants use once-through cooling systems Gwhich simply withdraw water, run it through the cooling system and then discharge it back into the river, lake or estuary from which it was drawn.
About 43 percent of the nation's power plants still rely on this outdated cooling technology, but concerns about droughts, impacts on aquatic life and federal rules requiring decidedly less water-reliant closed-cycle cooling #GL_2082 at new power plants are eliminating once-through cooling technology as an option.
While closed-cycle cooling requires 93 to 98 percent less water than once-through systems, power plants still need lots of cooling water. Wastewater treatment plants are already filling that need in some areas.
San Antonio, Texas has been a pioneer of wastewater reuse (also called reclaimed water). Since the 1960s the city's wastewater treatment plant has been providing water to the city's energy utility. Today the San Antonio Water System provides up to 16 billion gallons per year for cooling at CPS Energy's power plants.
The poster child of wastewater reuse at power plants is the Palo Verde Nuclear Generating Station in Arizona. The onsite wastewater treatment center at the largest nuclear power plant in the US can process up to 90 million gallons of pre-treated wastewater every day from five nearby cities, providing 100 percentof the plant's cooling needs.
Despite these and other successful examples of cooperation between water and energy utilities, only 60 of the 5,400 power plants in the US get their cooling water from treated municipal wastewater sources. Most of those power plants are located in the thirsty states of Florida, California, Texas and Arizona, with a few found in Massachusetts, Mississippi, New York and Wisconsin.
So why such paltry cooperation between two utilities that could help each other out? Experts from electric utilities, municipal wastewater treatment facilities and research organizations met at a workshop in 2012 to discuss just that. They found four common barriers that are making it difficult to work together:
- Regulations: Conflicting regulations enforced by different regulatory agencies can make it difficult for projects to get underway.
- Poor Communication: Despite successful examples of wastewater reuse projects at electric utilities, there are few opportunities to share lessons learned and best practices have yet to be established to provide guidance.
- Risk Aversion: Electric utilities tend to be conservative in nature, so because the cost to switch to reclaimed water can be high, and familiarity with wastewater reuse is low, a strong business case must be made to overcome risk aversion.
- Culture Clash: Because many electric utilities are for-profit businesses and wastewater treatment plants are often owned by municipalities or state authorities, there can be misunderstandings between the two different cultures.
The 2012 report presents six steps to encourage more cooperation between treatment plants and power plants. Underlying all six is the need for more integrated water and energy planning, a big part of what we like to call the nexus approach.
If these barriers are overcome and municipal wastewater and electric utilities collaborate and coordinate their efforts, what's the potential? A 2009 study found that 50 percent of existing power plants can obtain all of their cooling water from wastewater treatment plants within a 10 mile radius, and that jumps to 76 percent if the radius is extended to 25 miles.
That should be music to the ears of power plant operators who could see their freshwater consumption for cooling increase by 336 percent in Florida, 207 percent in New York and 93 percent in New England. As I've written before, using recycled wastewater is not a perfect solution. Water is still transported to a different watershed, whether by pipeline or by evaporation, and reclaimed water doesn't reduce emissions or public health impacts from fossil fuel and nuclear power plants. But until we rely more on energy efficiency and renewable sources than on conventional power plants, this unlikely alliance between water and energy utilities can at least curb power plants' thirst for freshwater.