When it comes to running a water utility, saving water and saving energy mean pretty much the same thing. When water is wasted, so is the energy it took to pull the water from the source, treat it, and pump it up the water tower.
Other sectors — industrial, commercial, residential — are coming to that realization. And they’re seeing that it works the other way, too: Saving energy saves water. It’s a concept called the energy-water nexus. Sandia National Laboratories, on its Web site, says it this way:
“Energy production requires a reliable, abundant, and predictable source of water, a resource that is already in short supply throughout much of the U.S. and the world. The electricity industry is second only to agriculture as the largest user of water in the United States. Electricity production from fossil fuels and nuclear energy requires 190,000 million gallons of water per day, accounting for 39 percent of all freshwater withdrawals in the nation, with 71 percent of that going to fossil-fuel electricity generation alone.
“Coal, the most abundant fossil fuel, currently accounts for 52 percent of U.S. electricity generation, and each kWh generated from coal requires withdrawal of 25 gallons of water. That means U.S. citizens may indirectly depend upon as much water turning on the lights and running appliances as they directly use taking showers and watering lawns.”
Saving resources
Seeing the connection between water and energy automatically makes it more important to conserve both. We literally can’t have one without the other. Our nation has been serious for some time about conserving energy, and rising prices in recent years have added a sense of urgency.
On the other hand, many of us — especially in water-rich areas like the Great Lakes region where I live — have tended to think of water as cheap and abundant. Increasingly, it is neither. It’s one thing to read about water shortages in the Southwest and, more recently, the Southeast. It’s another to see, as I did a few years ago, the Rio Grande River reduced to a water-filled ditch from all the withdrawals along its course.
The need to conserve water has not escaped notice. That’s why we see all sorts of innovations in water reclamation, especially in drier areas of the nation. But the connection between water and energy is a newer realization, and it applies very directly to water and its treatment and distribution.
Maximum utility
The Water and Energy Technology Team (WETT) at Lawrence Berkeley National Laboratory says it clearly. “When water is used only once, then treated and discharged to the environment, for instance, through an ocean outfall as is still the practice in most coastal cities worldwide, the result is minimal resource utility, minimal resource recovery, and maximum compounded energy use.
“When water is reclaimed through advanced wastewater treatment and is then reused to offset the use of potable water for non-potable purposes such as irrigation and fire protection, water’s utility is increased. Moreover, the per-unit volume energy intensity associated with water collection, potable treatment, and distribution followed by wastewater collection, treatment, and reuse is decreased.
“In short, water reclamation and recycling save water and energy, while single-pass water use wastes water and energy. Matching water quality with its intended use achieves the greatest water and energy utility and efficiency, thereby minimizing depletion of these scarce resources. By offsetting the demand for new water resources, water reclamation and recycling reduce water consumption and the energy used in providing potable water.”
Fixing the pipes
The WETT might have added that the connection between water and energy makes it all the more important to fix the underground infrastructure that carries water and wastewater.
What is more wasteful, after all, than treating and pumping water, only to have it trickle out of the pipes and into the ground? What could be more wasteful than letting clear stormwater flow into sewer pipes, get dirty, and require treatment?
The energy-water nexus should give even more impetus to the need to invest money, equipment, and staff ingenuity in improving the underground infrastructure. In every facet of the water and wastewater sectors, we need to treat water and energy like the invaluable treasures they are. Here are the folks at Sandia National Labs again: “Electricity and water are at the heart of the U.S. economy and way of life. National defense, food production, human health, manufacturing, recreation, tourism, and the daily functioning of households all rely on a clean and affordable supply of one or both of them. Understanding the complex relationship between water and electricity and developing technologies to keep that relationship healthy is an important key to a sustainable and secure future for the United States.”
Comments on this column or about any article in this publication may be directed to editor Ted J. Rulseh, 800/257-7222 or editor@mswmag.com.
