Necessity being the mother of invention, as populations grow and climate patterns shift towards drought and deluge, one very basic need currently spawning a lot of invention is the need for water. While meeting the needs of thirsty people may be priority number one, thirsty power plants are spurring engineers to consider some unusual strategies to make sure that the lights stay on. More and more, those lights are depending on the water that’s pouring down drains and toilets.
Presumably wary of poop jokes, engineers and other technically-minded folk call this recycling of treated municipal wastewater “reclaimed water,” which is increasingly seen as a water source for uses ranging from golf course irrigation to cooling massive power plants (PDF).
Cooling for power plants and other industrial facilities is the largest use of reclaimed water, and the benefit of using this maligned but incredibly valuable water source is that it can reduce pressure on limited freshwater resources. Plus, it eliminates the need to suck in cooling water from rivers, lakes or estuaries, meaning that cooling a power plant no longer has to mean destroying aquatic life.
However, the process is not as simple as just laying a pipe between a treatment plant and a power plant and turning on the tap. If the wastewater isn’t treated properly, chemicals can corrode and damage equipment, and bacteria and other potentially harmful microorganisms can be released into the atmosphere through the plume of evaporated water rising out of a cooling tower.
There are no federal regulations specific to reclaimed water, and a 2004 EPA study – the most recent nationwide look into reclaimed water use – found that only nine states had regulations or requirements specific to the industrial reuse of wastewater. As one might expect, the regulations vary from state to state, but in general they require two things.
First, the reclaimed water has to receive tertiary treatment, which includes disinfection to kill bacteria and other pathogens. Where the reclaimed water is not already treated to meet those standards, power plants sometimes treat it onsite and other times plant owners simply pay the treatment facility to upgrade their equipment.
Second, power plants have to limit the exposure that the public might have to the cooling tower plume, either by requiring a certain distance between the plant and areas where people might be enjoying their day, or by requiring the plant to use particular technologies that keep the size of the plume to a minimum.
About 50 power plants across the United States use reclaimed water, and perhaps the poster child is the Palo Verde Nuclear Plant in Arizona, which draws in about 55 million gallons of wastewater per day from five nearby cities, far more than any other plant in the country. Not only does this keep the 3.7 gigawatt plant from tapping into already-stressed aquifers, but the cities will be paid $1 billion over the next 40 years by the plant’s owners for the privilege of using the cities' wastewater, turning a former burden into a bonanza.
As might be expected, reclaimed water use is common in arid southwestern states (Florida is also a big fan). But many states that would not usually be considered water-poor, like New Jersey, Massachusetts and Maryland, are wisely planning for the long term as evidenced by numerous power plants that are tapping into this recycled source not just for cooling but for water-dependent scrubbers that reduce emissions. Since the release of the 2004 EPA report, other states have jumped onto the reclaimed water bandwagon. New York, for example, passed a law in 2005 to establish reclaimed water regulations and standards. The rules haven’t been finished, but in a state with over 600 wastewater treatment plants, forward-thinking power plant owners are forging ahead anyway. A just-completed power plant near Albany uses water piped in from a nearby sewage treatment plant (PDF), and the Long Island Power Authority has discussed using reclaimed water in its recent ten-year electric resource plan.
And reclaimed water is not just used by fossil fuel and nuclear plants. The new Beacon Solar Energy Project in California, a massive utility-scale solar power plant, will pipe in 521 million gallons of reclaimed water per year from a neighboring community.
Is using reclaimed water a perfect solution? Maybe not. Water is still typically drawn from a source and transported to a different watershed, whether by pipeline or by evaporation. But in regions where water is scarce or growing demand is casting an ominous cloud over the future, power plant owners are exploring this time-tested option, and states are developing regulations to keep the process safe and sane – no one likes an airborne pathogen, after all. Necessity can be a persuasive mother when she wants to be, and the nation’s sometimes fragile water supply is demanding smarter choices, like taking the “waste” out of “wastewater.”