Direct potable reuse (DPR) is a vital component in water management strategy, especially in drought-prone areas of the United States. Beyond helping create water supplies that are more resistant to droughts, DPR also provides environmental advantages. Most importantly, new regulations are being promulgated to guarantee that the water produced is not only safe but will be cleaner than many of our current sources of drinking water.
Below, Geosyntec’s Brian Petty, PE, (California), Ken Susilo, PE, CPSWQ (California), Kirk Craig, PE (Arizona), and Jason Kerstiens, PE (Colorado), address questions occasioned by California approving new DPR guidelines.
The Answer Team
Meet our answer team, who provided expertise to address the key early questions our clients are asking and collaborated on the following answers.
Brian Petty is a Senior Principal Engineer with more than 23 years of experience focused on chemical and civil engineering related to water management, conveyance and treatment, and replenishment programs.
Ken Susilo is a Senior Principal Water Resources Engineer with more than 25 years of experience focused on integrated urban stormwater management.
Kirk Craig is a Senior Principal Engineer with more than 28 years of experience focused on designing and constructing water treatment systems, addressing emerging and recalcitrant compounds such as PFAS, and conducting remediation at industrial and commercial properties.
Jason Kerstiens is a Principal Civil and Environmental Engineer with more than 20 years of experience focused on process engineering, regulatory compliance, water resource optimization, and strategic planning.
Q&A
What is direct potable reuse and why is it important for California and for many other parts of the United States?
Direct potable reuse (DPR), also referred to as advanced water purification (AWP), is the introduction of highly treated recycled water from municipal wastewater treatment plants directly into public drinking water systems. DPR can help diversify and enhance not only California’s water supply, but also the water supplies of many other southwestern and midwestern states, as these regions face ever-growing challenges from a variety of environmental and infrastructure issues, including the impacts of climate change and increasingly severe droughts.
How are DPR regulations developed and implemented in California and other states?
After several years of careful studies and community outreach, on August 6, 2024, California’s Office of Administrative Law approved the DPR regulations adopted by the State Water Resources Control Board on December 19, 2023. The State Water Board adopted DPR regulations after conducting a feasibility study, consulting with an expert panel and an advisory group, soliciting public comments, and undergoing a peer review.
The DPR regulations, which will be effective on October 1, 2024, establish criteria for the treatment, monitoring, and permitting of DPR projects. The criteria and implementation process described in the DPR regulations are extremely protective of public health. A number of other states including Colorado, Arizona, Florida, and Texas are also at working on developing DPR and AWP regulations. These states’ regulations are in various stages of development and implementation.
How is DPR different from indirect potable reuse?
Indirect potable reuse (IPR) is when recycled wastewater is used to replenish groundwater aquifers or water bodies that are sources of drinking water. IPR involves using an environmental buffer, like soil or groundwater, between the discharge point of treated recycled water and the intake to a drinking water treatment plant. The buffer provides additional reliability and protection for public health. DPR does not include requirements for an environmental buffer. Instead, the regulations require exceptionally robust treatment and monitoring.
How is the safety and quality of DPR water ensured?
The DPR regulations require that the recycled water meets all standards for drinking water and is of higher quality than many existing sources. The DPR regulations also specify certain tried-and-true treatment processes. These include advanced treatment processes in excess of those at most current wastewater or drinking water facilities, rigorous operational and performance requirements, and advanced water quality monitoring. They also include stringent response requirements if potential upsets are detected and detailed reporting and recordkeeping obligations.
The DPR regulations are based on the recommendations of independent expert panels, advisory groups, and community members that evaluated the scientific and technical aspects of DPR.
What expertise can Geosyntec offer regarding DPR initiatives?
Notably, the state of Arizona relied on Geosyntec experts to lead the development of the Advanced Water Purification Roadmap, a resource for stakeholders pursuing DPR and AWP initiatives. The Roadmap lays out standards, treatment performance requirements, design criteria, operations obligations, and monitoring and reporting.
In addition to the Roadmap, Geosyntec personnel recently helped Arizona develop a draft guidance manual that describes the process an AWP program applicant would follow to select specific treatment processes in an advanced water treatment facility. The manual includes chemical and pathogen treatment requirements, membrane-based unit process descriptions, final disinfection requirements, example treatment trains, system-planning criteria and considerations, pilot-testing guidance, design criteria for addressing failure-response time, and general engineering timelines and best practices.
How has Geosyntec already supported such projects? And what does that mean for future clients?
In California, we have supported water agencies’ IPR programs and industrial businesses’ water replenishment projects intended to beneficially reuse valuable treated wastewater. Because Geosyntec has decades of experience supporting industrial clients with water reuse and resource recovery, we bring a deep understanding of the composition and treatment options for complex domestic and industrial wastewater.
Our ability to bridge the gap between the domestic and industrial sewer dischargers and the downstream wastewater treatment infrastructure (and pending DPR-related modifications) has allowed our clients at public water agencies and industrial clients to proactively prepare for the changes occasioned by the DPR regulations. Clients benefit from our range of expertise, which uniquely equips us to help them pursue cost-effective and protective strategies built on holistic approaches.
More Information
To learn more about how Geosyntec can support your DPR and AWP projects, reach out to Brian at BPetty@Geosyntec.com, Ken at KSusilo@Geosyntec.com, Kirk at KCraig@Geosyntec.com, or Jason at JKerstiens@Geosyntec.com.
Learn more about Brian Petty.
Learn more about Ken Susilo.
Learn more about Kirk Craig.
Learn more about Jason Kerstiens.
