The Importance of Reusing Water in Arizona Is Growing As Other Sources Become More Scarce

By John D. Burnside, Fred Breedlove, John Habib, and L. William Staudenmaier

It seems that not a day goes by without another news story bringing Arizona to the forefront of a national dialogue about water security in a time of drought, changing climate, and growing population. This article is Part 6 of Snell & Wilmer's series providing context for that dialogue as it applies to Arizona's diverse and resilient water supplies. Following an introduction, prior articles have discussed groundwater, in-state surface water, Colorado River water, and long-term storage credits. This article turns to reclaimed water — another important source of water in Arizona. The importance of reclaimed water will increase in coming years alongside advances in technology, an updated regulatory framework, public acceptance of reclaimed water as a component of municipal supply, and greater demand and scarcity in Arizona's other water supplies.

What is reclaimed water?

Arizona law defines reclaimed water as water that has been treated or processed by a wastewater treatment plant. See A.R.S. § 49-201(41). In practical terms, reclaimed water — sometimes referred to as "treated wastewater" or "effluent" — is water that is used, treated, and used again. According to the Arizona Department of Water Resources, reclaimed water makes up 5% of Arizona's water supply. While this percentage is small relative to other sources, it is nevertheless important, and this importance will grow.

At the present time, almost all reclaimed water in Arizona is treated to a quality suitable for non-potable uses only. Reclaimed water is typically used for agriculture, golf courses, parks, industrial cooling, maintenance of wildlife areas, or is stored underground to earn long-term storage credits (as described in Part 5 of this series). It is important to note that many of the golf courses and other turf areas that draw recreation-seekers to this state are not watered with precious potable water, but instead receive reclaimed water. Scottsdale, for example, operates a water campus capable of delivering 20 million gallons of non-potable water each day for turf irrigation. Scottsdale's system provides reclaimed water to 23 golf courses, including the Tournament Players Club in North Scottsdale, where the Phoenix Open is played each year. For another example, the City of Tucson has over 173 miles of pipes that serve over 1,000 customers, including schools, parks, and golf courses, with over 30 million gallons of reclaimed water per day during the summer. If you have ever visited and admired the mall area at the University of Arizona campus, you have seen the beneficial use of reclaimed water.

The Legal Framework

Prior articles in this series discussed the legal frameworks allocating the right to use groundwater, in-state surface water, and Colorado River water among the state's many agricultural, municipal, commercial, and industrial users. Thanks to a 1989 decision of the Arizona Supreme Court, reclaimed water is subject to its own legal framework, rather than the law governing the right to use the original source of water — such as groundwater or surface water — from which reclaimed water is derived. See Arizona Public Service v. Long, 160 Ariz. 429 (1989). The decision in Long held that entities generating reclaimed water have the legal right to use and sell the reclaimed water for any legal purpose and opened the door to the modern system of reclaimed water.

Long addressed a contract whereby several Arizona cities agreed to provide wastewater from a municipal treatment plant to utilities for the cooling of electric generator stations. Users of surface water downstream of the treatment plant sued the cities and utilities alleging that their arrangement violated the prior appropriation doctrine. Previously, the cities had discharged their municipal wastewater into surface water channels, where downstream users appropriated it for agricultural use. The municipal wastewater was derived in part from source water provided to each city by the Salt River Project (SRP), which acquired the source water and delivered it to each city by exercising groundwater and surface water rights (as described in Part 3 of this series). The plaintiffs that challenged this contract asserted that the portion of the wastewater derived from surface water remained surface water and was subject to the prior appropriation doctrine, and that the portion derived from groundwater remained groundwater and was subject to the Arizona Groundwater Code. The court rejected these arguments and upheld the contract, ruling that the reclaimed water was legally separate and distinct from either surface water or groundwater, that it would remain distinct until it was mixed with either surface water or groundwater, and that the cities could put the water to any use they saw fit, including selling it to the utilities.

By clearing the way for the cities to use their municipal wastewater free of the prior appropriation doctrine, the Long decision provided justification for investment in treatment technology and infrastructure to facilitate the distribution and beneficial use of reclaimed water, such as the Scottsdale and Tucson projects described above.

Regulation of Reclaimed Water

The use of reclaimed water is subject to regulation by the Arizona Department of Environmental Quality (ADEQ) to ensure that its use is protective of public health and the environment. Arizona Administrative Code R18-11-301 divides reclaimed water into several classes depending on the level of processing it has undergone, the level of pollutants and chemicals it contains, and the frequency with which it is tested.

Reclaimed water may also be used for an unlisted type of direct reuse, such as power plant cooling (as in the Long case) provided the person seeking to reuse the reclaimed water makes an application to the ADEQ. The Department will consider a variety of factors in determining whether and how to allow and to condition the proposed new reuse.

Direct Potable Reuse

As Arizona's demands on existing water sources increase, expect to see an increase in the number of ways that reclaimed water is put to use. The above discussion has focused on the use of reclaimed water for non-potable purposes. The next frontier for reclaimed water is "direct potable reuse," in which recycled water is treated with advanced technology making it safe for human consumption. This technology, sometimes referred to as "toilet to tap," will likely gain acceptance in Arizona and other areas with scarce water supplies in years ahead.

ADEQ is currently developing a regulatory framework for large-scale direct potable reuse. ADEQ commenced the rulemaking process in June 2022 and is currently wrapping up its engagement with a technical advisory group. Although potable reuse is already allowed under ADEQ's rules in Arizona Administrative Code Title 18, Chapter 9, Article 7, ADEQ plans to increase regulatory specificity and allow expansion of potable reuse for facilities subject to the federal Safe Drinking Water Act, including municipal service providers. ADEQ has set a target of December 31, 2023 to issue a notice of proposed rulemaking. Further, multiple Arizona cities are already exploring a collaborative effort to develop an advanced water purification facility for direct potable reuse that could produce enough drinking water for 200,000 people. Ultimately, it may take a large-scale education effort to convince a wary public that a "toilet to tap" water supply will be consistently safe. Once established, however, the benefits of large-scale direct potable reuse will be substantial in offering a drought-proof, reliable water supply that grows along with the population served.

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