I’ll drink to that
For generations, water and wastewater utilities have remained completely separate, but thanks to a changing climate and continued development, the divisions between those areas, like the water supply itself, are dwindling. Along with conservation and desalination of brackish water from wells or seawater, water reuse continues to be a leading solution to water supply challenges.
“The future of water supply for communities is reclaimed or recycled water,” says Craig Riley, water reclamation and reuse program lead at the Washington State Department of Health and vice-chair of the Alexandria, Va.-based Water Environment Federation’s Water Reuse Committee. “Climate change will drive a lot of the need. Regardless of perceptions, precipitation patterns are changing, and that means collecting and managing water from nature will be a bigger challenge. And, we know that groundwater is being withdrawn in developed areas much faster than it’s replenished. Reusing what has been withdrawn and used previously is the only high volume available — roughly 60 percent to 85 percent of the original withdrawal.”
While water reuse offers the greatest volume of usable water and continues to gain the acceptance of utility personnel and the public, communities across the country are finding ways to blend various solutions to meet the challenges they face.
The Everglades squeeze Miami-Dade
In Miami, public water historically has come exclusively from the Biscayne Aquifer, an abundant source of high-quality water that is part of the Everglades water system, says Douglas Yoder, deputy director of the Miami-Dade Water and Sewer Department. But, when the department applied to renew and expand its water use permits from the state in 2005, the state determined that additional withdrawals from the Biscayne would adversely affect the Everglades system.
To meet its 347 million-gallons-per-day requirement to serve its 2.3 million customers, the department developed a 20-year water supply plan that includes conservation, desalination of brackish water from a deeper aquifer and reclamation of wastewater. The goal of that reclamation project is “largely to replenish the Biscayne Aquifer so that we can withdraw a corresponding quantity of water to treat at a water treatment plant and distribute to our customers,” Yoder says. “Our 20-year water use permit contemplates that we will reclaim and reuse up to 170 million gallons per day of wastewater for this and other purposes.”
The city’s South District Water Reclamation Facility, currently in design, is the first phase of its reuse effort. The facility, estimated to cost $357 million, will process about 27 million gallons per day of tertiary treated wastewater through microfiltration, reverse osmosis, ultra-violet disinfection with the addition of hydrogen peroxide, and ion exchange to reduce ammonia levels. About 21 million gallons per day of the treated water will be pumped nine miles away to a series of injection wells.
The first of its kind in Florida, the system is expected to be operational by the end of 2014. “The water will travel and blend with the natural groundwater for about two years before it will be pumped from wells to a membrane softening water treatment plant that will produce about 18 million gallons per day of finished drinking water,” Yoder says. “While this is a relatively expensive source of water supply, it is ‘drought-proof’ in an area that experiences recurring drought cycles. The reclaimed water will meet all drinking water standards when it leaves the treatment facility, but the mixing with natural groundwater, the travel time to the drinking water wells, and the additional treatment at the drinking water plant will provide multiple barriers to any type of contamination problem.”
Anticipated population growth also is addressed in the plan, with the estimated extra 100 million gallons coming from water reclamation (70 percent), conservation (20 percent) and the desalination of the brackish Floridian aquifer (10 percent). The municipality also is planning to use Aquifer Storage and Recovery (ASR) to pump surplus water during the summer wet season into the Floridian aquifer and recover that water during the winter dry season to further relieve stress on the Everglades system.
Southeast Florida also is very sensitive to sea level rise because of the drainage system that carries stormwater into Biscayne Bay, Yoder says. “Sea level rise resulting from climate change could cause increased flooding and, due to the very direct hydraulic connection between the salt water and the fresh water, salt intrusion is a very real threat,” he says. “We are currently developing a surface water/groundwater model to evaluate salt intrusion and drainage issues that may occur as sea level rises.”
Early in the reuse game
Desert areas, like El Paso, Texas, have had to preserve their water supplies for decades. As early as 1963, the city was delivering reclaimed water to its community for industrial use and landscape irrigation. Today, El Paso Water Utilities (EPWU) supplies local golf courses, city parks, school grounds, apartment landscapes, and construction and industrial sites with more than 5.25 million gallons per day of reclaimed water. Reclaimed water also is used to operate treatment plants and to recharge the Hueco Bolson, a potable aquifer, through injection wells and infiltration basins.
In recent years, the water level in the Hueco Bolson has been decreasing, and brackish water has been interfering with the potable water, says Don Vandertulip, a consultant with Camp Dresser McKee (CDM), which has worked extensively with El Paso on water treatment projects. To combat the problem, EPWU has constructed the largest inland desalination plant in the United States, which intercepts the brackish groundwater and treats it with reverse osmosis. That treated brackish water then can be used to supplement the city’s potable water supply.
It is a perfect example of using technology to solve a specific issue in a unique community, Vandertulip says. “If El Paso had not put in the desalination plant, the potable water would not be useful anymore,” he says.
Austin, Texas, has had a reclaimed water program in place since 1974. “A lot of the early projects just made sense,” says Dan Pedersen, Austin’s manager of the reclaimed water. “We’d have a wastewater plant right next to a golf course, so it just made sense to use treated water for irrigation.”
But in 2000, the city made reclaimed water use part of its citywide water supply strategy. “It became apparent that we would need another potable water plant,” Pedersen says. “Reclaimed water was seen as a way to defer the construction of that, so we started building storage units and running pipelines.”
During the past 10 years, Austin has added a North Reuse system at Walnut Creek that includes a pump station and a clear well to store filtered effluent water, piping mains to Morris Williams Golf Course and the Mueller Redevelopment area, and the recently completed 51st Street Elevated Storage Tank. The system processes 75 million gallons per day, which provides for a variety of non-potable uses.
A new potable water plant is slated to come online by 2014, so Austin has no current plans to treat its reclaimed water to potable standards. “We’re fortunate because we have strong river rights, and we do have access to long-term water supplies,” Pedersen says. “But, we are trying to be good stewards of those resources, and using reclaimed water helps us to do that.”
Atlanta area water reached limits
Only a couple years ago, the Atlanta area suffered through a drought that highlighted the need for alternatives to its dependence on Lake Lanier. Recently, one of Atlanta’s metro counties, Gwinnett, built an advanced water reclamation facility that recycles 60 million gallons per day, with a goal of returning 40 million gallons per day to the lake.
“Since Lake Lanier is our raw water supply, we hoped to get credit for the return flows,” says Tyler Richards, deputy director of operations and environmental services at Gwinnett County Water Resources. Currently, approval for that credit is still in negotiations. In the meantime, several nearby golf courses and parks are using the reclaimed water from the Gwinnett facility. However, the utility has stopped accepting new reuse customers “since the goal is to return water back to the source rather than spray it on grassy areas,” Richards says.
As the “water wars” over raw water supplies continue between Alabama, Georgia and Florida, Gwinnett County’s future plans for water supply challenges are “in a state of flux,” Richards says. But, with the new water reclamation facility already online, Richards does not doubt that reclaimed water will continue to be part of the area’s solution.
Riley, too, believes that increasing numbers of municipalities will begin blending the management of water and wastewater to successfully meet water supply challenges. “The future will require a great deal of change regarding our concepts of municipal water supply and wastewater management,” he says. “Our current approach is to compartmentalize water, wastewater and stormwater into separate and very distinct utility operations. Reclaimed or recycled water is the hybrid utility. And, the future will show that joint, coordinated management of water and wastewater can result in lower overall capital costs, lower operations costs, more reliable water supplies and more certainty in responding to community growth.”
- Read the “Alternatives to water reuse” sidebar to learn more.
Nancy Jackson is a Huntsville, Ala.-based freelance writer.