POTABLE REUSE RESEARCH AND INNOVATION OVER THE LAST 50 YEARS AT WRF AND IN THE US

By Mrs. Julie Minton, Research Unit Leader at The Water Research Foundation

Water reuse is the practice of recycling wastewater for a beneficial purpose – whether for urban areas, agriculture, environment, industry, or drinking. This article is focused on potable reuse (purifying recycled water for the purpose of augmenting drinking supply (Figure 1) and its tremendous progress in the US over the last 50 years. Drivers vary, often dependent on local factors, e.g., water scarcity/abundance, population growth, groundwater subsidence/ prevention of saltwater intrusion, nutrient discharge restrictions, and a cultural shift in ensuring a circular economy through a One Water Approach (figure 2). There are no national regulations for reuse, however the US Environmental Protection Agency (EPA) released guidelines for water reuse in 1980; with updates issued in 1992, 2004, and 2012. In 2017, EPA issued a Potable Reuse Compendium providing a technical compilation of the current state of potable water reuse in the United States. With this guidance and the guardrails of the Clean Water Act (CWA) and The Safe Drinking Water Act (SDWA), states develop their own potable and non-potable reuse regulations. Each state has taken a different approach to reflect regional needs and drivers.

A number of states have successfully developed pathways for permitting potable reuse projects that are protective of public health. This success is a result of proven advanced treatment technologies, guidance from EPA, and research, including that of The Water Research Foundation (WRF). There are dozens of successful potable reuse projects across the US, and several are featured in Figure 3.

Research and innovation in advanced treatment technologies, robust monitoring and quality control measures, and communication on this purification process with both the public and key stakeholders has led to these successful projects and more to come. There is a wealth of experience and knowledge from decades of research and existing projects based on extensive work by federal agencies, WRF, utilities, and universities. Some of these seminal WRF research projects include:

-WRF 4765 Failsafe Potable Reuse at the Advanced Water Purification Demonstration Facility. In this 4-year study at San Diego’s 1MGD DPR demonstration facility, performance data were used in a quantitative microbial risk assessment to demonstrate that a full-scale DPR treatment train could reliably meet performance goals and produce a water that provides public health protection equivalent to, or greater than, conventional drinking water supplies. This study was co-funded by San Diego County Water Authority and paved the way for San Diego’s multi-phased Pure Water Program that will provide almost half of their water supply by 2035.

-WRF 1717 Potable Reuse Research

Compilation: Synthesis of Findings. This report summarizes key issues and findings from WRF’s $24M research portfolio of 34 projects that investigated the technical feasibility of implementing direct potable reuse projects, as well as the results of complementary research, to provide a clear understanding of the state-of-the-science on DPR and to identify unknowns that may require further research.

The report can serve as an accessible resource to communities and decision makers seeking more information on potable reuse, particularly DPR.

-WRF’s partnership with California State Water Resources Control Board (SWB). In 2018, WRF received a grant totaling $4.5M from the SWB to support non-potable and potable reuse research (leveraged to over $7M by MWD,

WRF, and other stakeholders). The first grant ($1.4M, D1705002) funds 5 projects which were recommended by the SWB Expert Panel in their report on the feasibility of developing criteria for DPR (Figure 4). The research findings are being used to develop regulations for DPR, driven by CA legislation SB 574 (2017), which established a deadline of 2023. The second grant (D1705003) uses the WRF Research Priority Program process to fund $3.1M for 20 projects on potable and non-potable reuse which are published or will be by early 2024.