Expanding Drinking Water Options

Technology_Assessment_MedallionProviding clean and fresh water is one of the most essential municipal services. Recent reports about lead-contaminated drinking water in Flint, Michigan and ongoing drought in several parts of the nation, highlight the importance of ensuring the public has a safe and abundant water supply.

Today’s WatchBlog shares the results of our latest technology assessment on what municipal utilities can do to address fresh water scarcity.

The water cycle

Fresh water resources renew themselves in a cyclical manner.

Figure 1 The Hydrologic Cycle(Excerpted from GAO-16-474)

But to meet the increasing demands of business and residents across the nation, we may need more water than nature can provide—and renew.

Using water more efficiently

To help reduce demand on existing water supplies, water utilities can make sure they’re making the most use of the water they have. We found 4 key ways that utilities can be more efficient.

  1. Detecting leaks. An estimated 2.5 trillion gallons—16%—of water withdrawn for municipal use is lost each year to distribution system leaks before reaching the tap. Unfortunately, most leaks go undetected because pipes are underground.However, utilities can use meters to detect hidden leaks. If installed at strategic points in a water distribution system, meters can measure the flow of water—and spot changes in flow that could mean there’s an unseen leak or other problem.
  2. Assessing the condition of water pipes. Old, corroded pipes can slow the flow of water, requiring more water pressure to pump through, which, in turn, can cause pipes to fail. EPA estimated that it would cost $384 billion over the next 20 years to replace all failing water infrastructure in the U.S. While there’s no one-size-fits all solution for this, especially given that pipes can be made from steel, concrete, cast iron, and other materials, utilities can prioritize and schedule inspections, repairs, and replacements.
  3. Managing water pressure. Sudden changes in water pressure or routinely high pressures can stress pipes and cause them to break. Some utilities use software programs to detect changes in pressure and traditional hardware is also available to measure and control pressure.
  4. Metering. Water meters aren’t just there to charge you for the amount of water you use. Meters also help detect breaks and leaks, and generate data that can help with water planning. New meters allow automated meter reading and can also alert central stations about any sudden changes.

Making water from waste

Some communities are also re-thinking the typical “once-through” municipal water cycle, in which water flows from its source once through the system, and any wastewater gets treated and released back in to the environment.

Figure 2 The municipal water cycle(Excerpted from GAO-16-474)

Instead, utilities can try to make more fresh water by either reusing treated wastewater or capturing storm water. Turning salty water fresh is also an option; however, desalinating water currently requires a lot of money and energy. The city of Los Angeles estimated that desalination could cost between $3,900 and more than $6,000 per million gallons, making it more expensive per gallon than conserving water or capturing storm water.

Cost is not the only factor limiting the use of these technologies. Nontraditional water source options aren’t very popular in the United States and few utilities are using them. This is in part due to the “ick” factor of drinking recycled water—even when it’s been treated and is safe to drink. However, many places in the U.S. are already practicing de facto reuse because the source of their drinking water is downstream from where another community discharges its wastewater.

Figure 6 Estimated percentage of utilities treating nontraditional water sources for municipal use, by EPA region(Excerpted from GAO-16-474)

We found that utilities serving large numbers of residential customers, or are in water-stressed areas, are more likely to use nontraditional water sources. Utilities that are already managing wastewater or storm water are also more likely to use nontraditional sources.

For details on the tech available to treat water, hurdles to nontraditional water use, and lots more facts and figures, check out the full tech assessment.

  • Questions on the content of this post? Contact our Chief Scientist, Dr. Tim Persons at personst@gao.gov.
  • Comments on GAO’s WatchBlog? Contact blog@gao.gov.
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