By Karina Aslanyan
In Scottsdale, AZ, the city’s Advanced Wastewater Treatment Plant – otherwise known as the Water Campus – sewage water flows in and drinking-quality water flows out. Although the recycled water is not likely to flow through household taps anytime soon, the plant is now demonstrating a small but important answer to recycling water in drought-plagued Arizona.
“We are one of the most advanced indirect potable reuse facilities in the world,” said David Walby, Water Reclamation Services Director at the Treatment Plant.
Arizona is at the fulcrum of two important and clashing trends: it is both one of the fastest growing states in the country and it is at the center of a water crisis in the American Southwest that is having rippling effects nationwide.
In May, the federal government announced plans to keep more water in Lake Powell on the Arizona-Utah border, instead of releasing it to Lake Mead in Nevada—the first time the government has taken such action, which will lead to cuts in water people can use in Arizona and elsewhere. Officials say that both reservoirs are at their lowest points ever.
Amidst this crisis, recycled water has become a key part of the water-shortage solution for many cities. Every year, the Water Campus returns over 1.7 billion gallons of purified recycled water into regional aquifers, via the Advanced Wastewater Treatment Plant. AWT can treat up to 20 million gallons of water a day, making it one of the largest indirect potable water reuse facilities in the world. The AWT takes so-called tertiary effluent water, which has already been recycled for irrigation purposes, and further purifies it using membrane ultrafiltration, reverse osmosis, and ultraviolet photolysis.
To understand the problem that the AWT plant is trying to address, it’s important to understand where Arizona’s water supply comes from and why those sources are now endangered. Today, Arizona is in the midst of a 20-year megadrought, brought on by the decline of the Colorado River, the state’s main source of drinking water. Additionally, the river supplies water to seven other states and Mexico. Around 40 million people rely on the river as a primary source of water for both indoor and outdoor use. Produce like lettuce, vegetables, and fruit are all reliant on the Colorado River, which irrigates over 5 million acres of agriculture in Arizona, California, and Mexico alone.
In Arizona, water coming from the Colorado River, as well as ground water, follows a strict allocation system that gives priority to large cities – like Phoenix and surrounding Chandler and Scottsdale – as well as Native American tribes. The latter won their allocations via the 1908 Supreme Court decision in Winters v. United States. Despite this, many tribes still suffer from water scarcity due to issues such as lack of water infrastructure. As a result of a complicated history of agreements with the state government, farmers in Arizona are last in line for Colorado River water and bear the brunt of the drought.
“There’s a need to move away from relying on Colorado River supplies as the primary supply of water,” said Sarah Porter, Director of the Kyl Center for Water Policy at Morrison Institute of Arizona State University. “We have to somehow make an adjustment to having a lot less water from the Colorado River, and that’s tough.”
Outside of recycled water, Arizona has also turned to ground water, which is being rapidly depleted, leaving a grim impact on the environment. The extraction of ground water creates fissures and subsidence – land sinking when the water that was filling a void within the ground is removed. “We have some areas in the valley where we have subsidence of upwards of 15-16 feet,” noted Walby.
To prevent the depletion of groundwater, Arizona passed the Groundwater Management Act in 1980. The act limits the use of mining water and requires that water taken from the ground be replaced to prevent subsidence.
One of the treatment plant’s major objectives is to replenish the aquifer holding ground water. What may come as a surprise, however, is that their only other objective is supplying water to golf courses. Through what is a public-private partnership known as the Reclaimed Water Distribution System, the Water Campus delivers 20 million gallons of recycled water to 23 golf courses in northern Scottsdale.
Golf courses are the biggest water users in Scottsdale and many other cities throughout Arizona; thus, they represent the Water Campus’s greatest opportunity for helping the municipality conserve water, according to Walby. One standard 18-hole golf course requires approximately a million gallons of water per day.
While Scottsdale’s golf courses may be its biggest users of outside water, they are also a huge economic engine, bringing in an estimated $500 million a year through tourism. While some golf courses have looked at introducing synthetic turf as an alternative to the high-maintenance grass, turf is not suited to the Arizona climate because it absorbs heat much more than grass.
Cities throughout the state have created incentives to encourage residents to preserve water used in outdoor irrigation, which accounts for about two-thirds of Arizona’s water usage, such as tiered water rates. That, in turn, is intended to reduce the prevalence of grass lawns, which require immense amounts of water to survive Arizona’s desert heat, which can reach as high as 122°F in summer.
“It’s a built-in incentive to go ahead and use the water that you need for indoors, but after a certain volume the next level of water is much more expensive,” explained Porter.
Additionally, cities like Scottsdale have been pushing residents to turn to native gardening. The city has introduced tax rebates for residents that choose to remove grass lawns and replace them with native vegetation, synthetic turf, or gravel.
The one place where the Water Campus’s recycled water is unlikely to flow, however, is in residential taps. In 2018 the Arizona Department of Environmental Quality permitted recycled water for direct potable reuse, which is defined as “the treatment and distribution of water without an environmental buffer.” (By contrast, indirect potable reuse means using “an environmental buffer, such as a lake, river, or a groundwater aquifer, before the water is treated at a drinking water treatment plant,” according to the EPA.)
Eighteen months later, in September of 2019, Scottsdale’s Water Campus was issued the state’s first permit for direct potable reuse. However, for now, Scottsdale is choosing to focus on replenishing its outdoor water supplies, perhaps a more palatable recycling goal for local residents.