How Does Reuse Fit Into Your Water Management Strategy?

By The Water Online Editorial Team

Whether an area is urban or rural, large or small, its water and wastewater treatment utilities face pressures ranging from supply scarcity and increasing operational costs to more stringent regulatory guidelines. These pressures have combined in recent years to shift the conversation around potable water reuse from a potential option to an increasingly important water management strategy. However, regulations that vary by state, cost concerns, and/or lack of a collaborative, regional water management strategy can sometimes prevent utilities from exploring reuse opportunities.

The decision to pursue potable water reuse, and the strategy for implementing it, is site-specific, but numerous instances of success have created a roadmap for regulators and utilities to better assess their needs and see firsthand the potential benefits of water reuse within their systems. Although non-potable reuse (NPR) “purple pipe” systems are common throughout the U.S., indirect potable reuse (IPR) and direct potable reuse (DPR) systems are now increasingly on the radar of utilities seeking to meet rising water demand and comply with evolving regulations.

Potable Reuse Flourishing Despite Stubborn Challenges

Water reuse is primarily regulated at the state level, with states establishing reuse-specific requirements within the broader federal regulatory framework, often developed in response to local or regional need. Since water supply scarcity is a major driver for water reuse, it is unsurprising that states in the Southwest are at the forefront of developing regulations applicable to potable reuse. Some states simply have not been pressured to update their water management regulations, making the establishment of a potable reuse program more difficult in those areas.

For utilities, potable reuse drivers include discharge avoidance and wastewater effluent management: effluent has historically been viewed as something to be disposed of, into lakes, rivers, or oceans, which has resulted in de facto reuse in some areas. However, in many parts of the U.S., effluent discharge limits (e.g., nutrient levels and temperature) are becoming a more significant regulatory issue, forcing utilities to adapt. 

Reuse programs are also a source of uncertainty. All utilities devise a range of dollars-per-kilogallon for potable reuse projects, but that range depends heavily on how challenging their scenario is. Potable reuse program costs are impacted by wastewater treatment plant improvements necessary to supply compliant effluent to an advanced water purification facility (AWPF), the size of that plant, the location, and regional infrastructure. Although water reuse data is increasingly available due to the prevalence of full-scale projects underway, these local conditions significantly impact the feasibility and cost of a potable reuse project. For example, a coastal utility and an inland utility will make different decisions regarding technology, generate distinct residuals, and experience dissimilar materials availability.

Further, with stricter regulation of maximum contaminant levels (MCLs) related to per- and polyfluoroalkyl substances (PFAS) and other effluent contaminants expected in the future, the cost of compliance is increasing so much that power use starts becoming an attractive alternative, versus trying to satisfy those limits. Site-to-site differences in source water, varying levels of treatment necessary to meet the regulated contaminants and pathogens in effluent, and the potential need to provide redundant systems in the name of public safety also contribute to preclude the possibility of accurately predicting reuse program costs.

Limited Knowledge And Resources Necessitate Collaboration

Any water resource plan should be built upon a holistic understanding of the regional watershed and informed by all entities with a purview of that water. Large reuse projects typically require multiple partners and institutional arrangements. Chartering with all stakeholders in the urban hydrologic cycle at the start of a reuse project creates opportunities for mutual planning, cost sharing, and more wide-ranging benefits.

Although some water management initiatives can be undertaken by utilities independently, potable water reuse demands early and consistent coordination between a utility and the communities it serves, regulators, and neighboring utilities, particularly those drawing from the same water supply. This collaboration is vital to determining which water reuse strategy, if any, is most advantageous for a given site.

Regulators are the most critical partners on these projects but, like the utilities they govern, they are usually working with limited resources. States may lack sufficient funding for staff to process permit applications or may not yet have a regulatory framework to facilitate the process. As more projects go through the permitting process and both utilities and regulators better understand the challenges, that experience helps pave the way for the next program, helping streamline the process for subsequent projects.

Data is available from projects of varying scales and lifecycles across the country, so it is vital that utilities, regulators, and states build on each other's previous work instead of reinventing the wheel with each project. Additionally, research from academic and private institutions is demonstrating solutions to site-specific challenges.

Water management typically is structured in silos: operations, engineering, permitting, wastewater treatment, distribution system, etc. Potable reuse projects demand that these silos, including regulators, either coalesce or establish efficient cross-department communication. The larger the project, the more important it is to have a clear vision from leadership and a project champion who can navigate the technical and political challenges.

Investigating Potable Reuse Feasibility And Options

Initial considerations for a potable reuse program include the characteristics of the source water, including the wastewater treatment plant effluent that will feed the advanced treatment process. Utilities should take a holistic approach, evaluating challenges and opportunities as well as potential partners, supply sources, and end uses. Consider, too, that regulatory standards related to nutrients and emerging contaminants, for example, are already driving large-scale system transformation, including National Pollutant Discharge Elimination System (NPDES) permitting and guidelines for effluent disposal.

Ultimately, the same drivers prompting investments in wastewater treatment plant effluent can also support the case for reuse, because the site is already investing to improve effluent water quality. Co-locating an AWPF at those sites may therefore be a logical next step. For example, in Northern California, any dischargers into the San Francisco Bay are subject to stringent nutrient limits. So that wastewater treatment plant and that funding stream bear the related cost regardless, taking some of the bite out of AWPF costs. Conversely, a smaller utility may require wastewater treatment plant upgrades to raise effluent quality to a level conducive to potable reuse, burdening the utility with expenses beyond simply building and establishing an AWPF.

Utilities also must examine the pros and cons of reverse osmosis-based (RO) versus carbon-based treatment trains. RO-based treatment is essentially considered the default for potable use in the U.S., but the RO treatment train can produce a concentrate stream representing roughly 15% to 20% of the incoming flow. So, if 10 million gallons per day (MGD) undergo that process, up to 2 MGD emerge concentrated with salts and other constituents that must be disposed of. A coastal utility may be able to put that flow into the ocean, but where can an inland-located facility send it?

Those disposal challenges and costs make carbon-based treatment systems more attractive to some utilities. Carbon-based treatment trains usually involve ozone-biological activated carbon (O₃/BAC) and may also include granular activated carbon (GAC) to remove contaminants. Utilities can pilot test carbon-based treatment trains alongside RO-based treatment, generating parallel data that indicate the costs, challenges, and effectiveness of each treatment approach in achieving the utility’s water quality goals.

Since not all reuse operates or costs the same, utilities must explore all their options among NPR, IPR, and DPR to determine which approach best fits local resources, including public perception and acceptability of different water qualities. Public perception is an often-overlooked but critical element of implementing a potable reuse program and can become a significant barrier when it is not addressed early. Public opinion is shaped by project scope, local conditions, and the utility’s effectiveness in engaging the community.

Utilities addressing near-term water supply issues may need more immediate, targeted public engagement. Longer planning horizons can provide additional time to build partnerships with neighboring utilities, regulators, and other stakeholders. For example, in Florida, utilities have committed to protecting wetlands and other fragile ecosystems in their public messaging and water management strategies. Potable reuse can be aligned with wetland rehydration, combining advanced treatment with natural ecosystems that draw different native species of birds and plants, perhaps be supported by a visitor’s center for public education or a park. Such opportunities may not be accessible to an individual, smaller utility, but partnerships with neighboring utilities can open those doors.

Potable Reuse Is Closer Than You Think

Most utilities are exploring the feasibility of reuse and their options for a more local, reliable source as they envision what their recycled water future looks like. In practice, this means reaching out to collaborate with nearby utilities and partners, proactively researching technology options, and advocating for state-specific and site-specific regulations that make sense for their local conditions.

As wastewater effluent regulations become more stringent, utilities are essentially moving toward a potable reuse treatment train already as they implement measures to meet MCL standards. Combined with demand projections that show a need for reuse in the future, the time to start planning their potable reuse future is now. To learn more, contact the contributing experts and watch the Water Online Live event, Closing The Loop: How Reuse Is Reshaping Water Management.

About The Experts

Jacqueline Mutter is the National One Water Planning Lead at HDR.

Fred Gerringer is the National Water Reuse Practice Leader at Brown and Caldwell.

Pranjali Kumar is Associate Vice President and Southeast Reuse Lead at Carollo Engineers.