Area plant treats sewage to return it to water cycle
EDITOR’S NOTE: The Denton Record-Chronicle staff and graduate students from the University of North Texas School of Journalism under the direction of professor George Getschow worked more than a year interviewing people across Texas and researching the issue of how people are using water, the state of this necessary resource and how some are searching for solutions. The series launches an ongoing effort to keep readers informed about how the drought is affecting daily lives across the state and how some are seeking alternative measures to solve a growing issue as the drought continues and the state attracts more residents. Look for the “Water Woes” logo throughout the next week and coming weeks and months. And if you have any suggestions, ideas or stories of your own to share, please visit our special projects page on Facebook or send an email to firstname.lastname@example.org.
— Dawn Cobb, managing editor
ROANOKE — The wind is howling across the wastewater treatment plant here — a sprawling maze of storage tanks, sludge grinders, bar screens, pumps and other heavy-duty equipment designed to remove human waste, diapers, baby wipes, drugs, toilet paper, parasites, viruses, fungi and other foul contaminants flowing in from pipelines across North Texas each day, transforming the raw sewage into “reusable water.”
It’s 40 degrees outside. But the cold doesn’t seem to bother John Bennett, who is dressed in a comfy cowhide jacket, white shirt, khaki pants and brown boots studded with spikes. But as a weird odor brushes by Bennett’s nostrils, the mild-mannered plant manager suddenly becomes agitated. Trying to pinpoint the location of the smell, Bennett sniffs around the plant like a police dog inspecting luggage for drugs. He reaches into his jacket and pulls out a walkie-talkie.
“I’ll need a team at Lift Station No. 3 and Preliminary Treatment Unit No. 2 to take some samples,” says Bennett, scrambling around the plant, searching for the source of the strange odor.
“Roger that,” a staticky voice responds over the walkie-talkie.
Within minutes, a truck with two men in blue shirts and navy pants pull up to Lift Station No. 3 at the Denton Creek Regional Wastewater System to help hunt down the smell. Bennett’s workers will spend the next few weeks inspecting and taking samples from 27 miles of wastewater piped into the plant from Fort Worth, Haslett, Keller, Northlake, Argyle, Flower Mound, Southlake, Westlake, Roanoke and two municipal utility districts, trying to identify the source of the smell.
Eventually, Bennett and his team will identify the pollutant: ethylene glycol, a chemical used for deicing airport runways and as an antifreeze agent in cooling and heating systems. Bennett will call officials in Fort Worth, asking them to track down the polluter and clamp down on the discharges, complaining that the chemical is creating havoc with his wastewater treatment, forcing him to curtail operations.
Sebastian Fichera, Fort Worth’s assistant director for resource recovery, quickly dispatches his inspection team to investigate Bennett’s complaint. The inspectors discover that the glycol discharges are coming from a nearby treatment plant, and Fichera orders the plant to implement new waste disposal practices that will prevent future discharges. Bennett is pleased that the case of the mysterious pollutant fouling up his plant is finally solved.
Until recently, few people paid any attention to the Trinity River Authority’s Denton Creek Regional Wastewater System. The plant began operations in 1990 on 48 secluded acres on U.S. Highway 377 in Roanoke, in southern Denton County. A few years ago, however, an upscale neighborhood sprouted across the street and the plant’s new neighbors soon started complaining about the foul odor of “rotten eggs” emanating from the plant. “When the wind hits north, the smell gets discomforting,” says Lisa Greco, who recently moved into Briarwyck.
Today, however, Bennett is pleased that Denton Creek and the Trinity River Authority’s other wastewater treatment plants in Texas are in the public spotlight — not because they stink, but because the state is heavily counting on them to provide a clean and sustainable water supply for the region’s growing population and industry, now and in the future. With Texas facing one of the most severe droughts in history — one that’s rapidly depleting the state’s reservoirs and underground aquifers — more and more municipalities are studying the use of treated wastewater to replace shrinking supplies of fresh water.
“Water is not recreating itself,” says Bennett. “We’re draining our underground aquifers and reservoirs. It’s not a source that’s going to be around forever. If we don’t have innovative ways to reuse and replenish it, that’s really going to be a problem.”
The Texas Water Development Board is sounding the same alarm. In its most recent report examining supply and demand between now and 2060, the authors were blunt about the imperiled state’s water resources: “In serious drought conditions, Texas does not and will not have enough water to meet the needs of its people, its businesses, and its agricultural operations.”
State water planners have devised various strategies to make up for the shortfall, including new reservoir construction, reallocation of water resources from water-rich regions to water-starved regions of the state, and desalination of brackish groundwater. But it would cost billions to build new reservoirs, desalination plants and pipelines to transport fresh water from remote parts of the country to population centers in Texas.
And that’s why state water planners see significant advantages in using “reclaimed” water to make up for diminishing supplies of fresh water. Wastewater treatment plants, they say, offer an opportunity for growing urban centers to recycle an abundant supply of sewage into a reliable supply of water that’s safe enough for human consumption.
Today, water reclamation supplies about 800,000 acre-feet per year, or 4 percent of Texas’ annual total water consumption. But reclaimed water use is growing rapidly. By 2060, state planners are counting on reclaimed water to furnish about 10 percent of all new water supplies.
But some water-starved cities in Texas, plagued by chronic drought, have already made recycled sewage the centerpiece of their conservation efforts, spending millions over the last three decades constructing wastewater treatment plants to help replenish dwindling supplies from rivers, reservoirs and aquifers.
Twenty-four years ago, for example, San Antonio committed to building the nation’s largest “recycled water delivery system.” Today, the city boasts a 130-mile loop of purple-colored pipelines that furnish reclaimed sewage water for cooling power plants, irrigating golf courses and athletic fields and bolstering the flow of water moving down the San Antonio River. Recycled sewage water, in fact, constitutes most of the water flowing through San Antonio’s famed tourist attraction, the River Walk.
“San Antonio’s beautiful River Walk area is thriving because of its backbone, the sustainable recycled water that flows through it,” Nancy Stone, the Environmental Protection Agency’s assistant administrator for water, says during a press conference following a tour of the upper reach of the river. “Recycled water provides life to this area, even during the drought.”
At the same time San Antonio is pumping millions of gallons of reclaimed sewage into the San Antonio River to keep a fleet of gondolas afloat along the River Walk, El Paso is pumping millions of gallons of it into its aquifer to prevent it from drying up altogether.
Fearing the Hueco Bolson Aquifer, the city’s principal source of fresh water, would be tapped out by 2015, El Paso built the Fred Harvey Reclamation Plant to feed recycled water to the exhausted aquifer through a series of injection wells and infiltration basins. The aquifer recharging project, begun in 1985, has given the Hueco Bolson a new lease on life and residents a more reliable source of water.
Though few of its residents realize it, the Dallas-Fort Worth region is also a major supplier and user of reclaimed sewage water. In 2010, recycled water supplied more than 48 billion gallons of water a day for some 6.5 million residents. And as the area’s population continues to grow, so will its reliance on recycled wastewater.
The Denton Creek Regional Wastewater System, operated by the Trinity River Authority, serves one of the fastest-growing areas of the state. Since the wastewater treatment plant opened in 1990, its capacity expanded from 0.75 million gallons of sewage daily to 11.5 million today — an increase of more than 1,400 percent. And another major expansion to 16.5 million gallons a day is on the drawing board.
Converting all that sewage into a clean, “reusable” water supply suitable for human consumption requires a level of physical, chemical and biological treatment that makes Louis Pasteur’s process to prevent bacterial contamination in food look like child’s play.
At the “headworks,” where 5.4 million gallons of raw sewage flows into the plant each day, giant screens and sludge grinders remove diapers, baby wipes, bandages, hygiene products, tires, empty chemical containers, plastic packaging, rusty paint cans, broken glass, plastic toys, tools, cables, spindles, syringes and a smelly array of other human and industrial wastes. “Anything you flush down the toilet or whatever waste is dumped in the sewage by industries, we’ll see,” says Bennett.
From the headworks station, the wastewater passes through a system of giant aeration basins, sedimentation tanks, rotating discs, clarifiers, centrifuges and other filtration equipment that removes dissolved and suspended organic matter, including dirt, grit and other fine particles. The next step in the treatment process is called “bionutrient removal.” This is where “the magic happens,” says Bennett.
During bionutrient removal, billions of bacteria found in the human stomach feed on organic material — a biological mass wastewater experts call “mixed liquor” — as well as ammonia, phosphorous, nitrogen and other contaminants. Bennett’s team keeps close vigil over the mixed liquor, watching to make sure it forms a bubbly, brown-colored brew — proof that billions of bacteria are digesting the “bad bacteria” and other contaminants.
Sounds simple, but it takes a trained eye, a sensitive nose and a well-balanced blend of nutrients to make sure the plant’s digestive system doesn’t develop a stomachache. “I’m cultivating the proper amount of food with the proper amount of air and the proper amount of bacteria to keep the younger and healthier bacteria active,” says Bennett. “Too much food, they [healthy bacteria] start dying off. Cut back too much air, they start dying off. If I have too much bacteria and not enough food and air for them, they start dying off. So it’s a juggling act to maintain the process.”
During race week at the Texas Motor Speedway, when 250,000 people pour into the Roanoke area three times a year, Bennett’s juggling act turns into a high-wire trapeze with no net. The plant doesn’t have the capacity to store the huge surge in sewage coming into the plant. So Bennett and his treatment team shift into high gear, scrambling round the clock to process the overflow of raw sewage.
Describing his method of handling a wave of ammonia, E. coli and other contaminants pouring into the plant during race week, Bennett sounds like a mad scientist. The week before the race, he says, he increases the plant’s healthy bacteria as high as he can, then cuts their food supply off. “So when the big wave of ammonia hits, my healthy bacteria are starving and they attack it,” he says. “And that way I can ensure the ammonia is removed.”
If E. coli or other “bad bacteria” escape Bennett’s battalion of healthy but starving “bugs,” nearly all of them will get electrocuted during the last stage of treatment by ultraviolet, high-intensity lights. The ultraviolet light “cooks it from the inside out,” says Bennett. “It’s very effective.”
Seven days a week, 365 days a year, 5.4 million gallons of reclaimed water, scrubbed of every contaminant except a few heavy metals, is released into Cade Branch, a tributary of Denton Creek that flows into Grapevine Lake. But only a fraction of that treated wastewater will be consumed locally. Most of it will join the flow of reclaimed water discharged from other wastewater treatment plants in the Dallas-Fort Worth area and travel 259 miles down the Trinity River to Lake Livingston, the principal water source for the 6.2 million residents of the Houston metropolitan area.
“You can’t work in this field and not look at the clean water leaving the plant and take some pride in that,” says Bennett. “What we do for the society and Mother Earth every day is just phenomenal, but nobody knows about it and we are OK with that.”
Well, some people know about it. Residents of Briarwyck, the plant’s neighbors directly across the street, haven’t stopped complaining about the smell of rotten eggs wafting over their $250,000 homes, their community pool and their children’s playground.
The plant has implemented a number of “odor-control measures” to pacify their neighbors. It’s planted a border of tall cedar trees between the plant and the neighborhood, attempting to block “adverse smells” from wafting over their fence. It’s installed three portable misters that emit a “perfume spray” to mask the pungent aromas of sewage. It’s injecting magnesium hydroxide, a chemical that stifles the smell of hydrogen sulfide — the gas that smells like rotten eggs — at various locations within and outside the plant. And it’s begun offering their neighbors tours of the plant to alleviate the anxieties over the foul smell hovering over their community.
Bennett and other tour guides explain that the “strong, unpleasant odor” coming from the plant is nothing to worry about. It’s just a natural byproduct of the digestion process. Beyond that, Bennett says there’s not much more he can do about the plant’s odor problem.
“At the end of the day,” he says, “I hope everyone understands that we are a wastewater treatment plant.”