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Thoughts From Engineers: Water Two Times Around and More

Chris Maeder on September 1, 2023 - in Articles, Column

In a cooperative undertaking among Florida’s wastewater and drinking-water sectors, rulemaking is moving forward to develop regulations and standards for the safe operation of potable reuse systems. In a country that for decades has operated centralized water-treatment systems to treat water principally for one application and one-time use, this is a significant development.

More importantly, the policy-making underway in Florida isn’t an outlier, but rather part of a larger reuse movement within Florida and the broader United States to push the limits on the use of greywater and blackwater. To use water in a more sustainable fashion—in multiple ways and through multiple cycles—is part of a national movement commonly known as One Water (uswateralliance.org/one-water).

Taking the Next Steps

Water reuse has been around for years, but it has been limited to reuse for non-consumptive purposes—land application and similar uses. As the current trend demonstrates, in several parts of the country the number of acceptable uses is expanding to include more applications. The state of California, for example, is developing a framework for decentralized reuse systems where water recirculates throughout one building for a variety of non-potable purposes. In June 2023, the Texas Legislature passed legislation to permit onsite treatment and reuse of blackwater for non-potable reuse. Resilience planning is a major driver behind these projects; actual water shortages in specific parts of the United States is another. If the growing number of 501(c)(3) organizations advocating for water reuse, national conferences, introduced bills in state legislatures and academic research at prestigious institutions is any indication, water reuse is a definite “thing,” and the movement looks to accelerate.

This column focuses on what’s arguably the “edgier” trend in the movement: the small but growing number of utilities that use innovative technologies to clean wastewater to high-enough standards to produce drinkable water. A lot is riding on making these pioneering systems work, and, so far, they’re a success, producing water whose quality is in many cases superior to most tap and bottled water. I personally find the water-reuse mindset encouraging; and not just because it reminds me of times in history when people recycled just about everything and did a lot more with less. The movement is a positive one because it recognizes water’s value—long overdue in the United States—and protects a resource critical to our long-term wellbeing.

The Utilities That Have Come Full Circle

Well before any other community in the United States, one of the first partnerships to provide clean drinking water from recycled wastewater came from a cooperative effort between California’s Orange County Water and Sanitation Districts. The resulting Groundwater Replenishment System (GWRS) was launched 15 years ago with a capacity of roughly 70 million gallons a day (uswateralliance.org/one-water) and is, to date, the world’s largest wastewater recycling facility in operation. A recent $284 million investment for facility expansion resulted in a capacity increase to 130 million gallons a day with clean water delivery to roughly 1 million people per day.

The facility is a prime example of a treatment center that uses an “indirect potable use” process to clean water. Very simply, wastewater that has been treated at the Orange County Sanitation District undergoes further purification treatment through a multi-stage filtration process and reverse osmosis, at which point it moves to a groundwater aquifer for a holding period. The Hampton Roads Sanitation District in Virginia uses a similar methodology via the Sustainable Water Initiative for Tomorrow (SWIFT) by diverting treated wastewater to the SWIFT plant where it undergoes further disinfection until it’s of drinking-water quality (hrsd.com/swift). At this point, it’s injected into the Potomac Aquifer, where it’s later withdrawn for distribution. In addition to providing drinkable water to large urban areas, the GWRS and SWIFT projects also were designed to address issues of saltwater intrusion and land subsidence, long-term problems that appear to have been resolved for the time being.

The facility at Reno, Nev., as part of the OneWater Nevada initiative (onewaternevada.com), will treat wastewater with charcoal filtration and ozonation prior to irrigation and groundwater storage applications, part of a multi-year trial phase. A water-purification process currently in use in Altamonte Springs, Fla., is the prototype for a demonstration project in South Jordan, Utah, where it will run as part of a comprehensive educational program. Both municipalities are presently vested in demonstration projects—wise in view of the high risk for misinformation—to thoroughly inform the public prior to bringing operations online. And there are more reuse projects in various stages of development throughout the country.

The wastewater facility in El Paso, Texas, as a “direct potable reuse” facility (epwater.org), doesn’t move wastewater through an environmental buffer or groundwater aquifer prior to further treatment. Rather, the wastewater is treated by reverse osmosis and UV filtration, along with other purification measures in a highly rigorous sterilization process, prior to sending the water back into drinking water lines. Currently, it represents one of the only direct potable reuse facilities currently in operation, but it won’t stay that way for long as Arizona and other states consider code updates.

Decentralized Use and Reuse Initiatives

Decentralized reuse systems for non-potable purposes are the subject of several state bills; the aforementioned Texas legislation is an excellent example. However, a full-fledged decentralized system with potable reuse is still some years away. Clearly, the public’s interest in bulletproof safety measures—rigorous licensing protocols for operators and meticulous design standards for the facilities in question—is significant. But as we consider where we’re going with water reuse, it’s important to remember the success we’re observing now.

The excellent record of existing potable reuse projects is due to the innovative technologies and processes that are no longer simply experimental. These pioneering utilities are working hard to supply high-quality water to millions of people. Several factors—from pilot and operational projects to high-quality research to the work of advocates for sustainable and resilient policy—are driving this important effort. It’s an exciting time to work in the water industry. 

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About Chris Maeder

Chris Maeder, P.E., M.S., CFM, is engineering director at CivilGEO Inc.; email: [email protected].

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