Effective Nutrient Management for Indirect Potable Reuse Systems

Authors:

  • Richard Cisterna, P.E. - Hazen and Sawyer

Indirect potable reuse (IPR) programs are expanding in several parts of the world. Most notably California has lead the way in the United States and Australia has forged ahead aggressively overseas in attempts to solve their severe water supply problems. Florida is not far behind, with water supply problems emerging throughout the state. These challenges are driving many utilities to seriously evaluate, and in many cases implement, indirect potable reuse programs.

One of the main drivers behind IPR programs is the need for large scale recycled water applications to meet the growing demand for alternative sources of water. In particular, California, and to a lesser extent Florida, are in serious need of addressing their water supply challenges. Irrigation systems are one part of the solution, but large scale groundwater recharge projects are a growing piece of the puzzle, as they can utilize large amounts of reclaimed water in a single project.

As such, new issues such as nutrient management and environmental impacts are beginning to arise when large amounts of recycled water are introduced into the water cycle. California’s new recycled water policy will require new projects to complete a nutrient management plan to assess the impacts of nutrients to their respective receiving basins. Similarly, many IPR projects in Florida are experiencing very stringent nutrient limitations due to unique hydrogeologic conditions that provide a close interaction between groundwater and sensitive surface water bodies. In some cases, nitrogen limits are approaching 1ppm and phosphorous limits are being squeezed to non-detect. These extremely low nutrient limits are forcing utilities to explore new and innovative solutions to address these emerging requirements.

The purpose of this paper is to review the state of emerging drivers and requirements concerning nutrients for indirect potable reuse projects in California and Florida, including the new California Recycled Water Policy and emerging stringent requirements in Florida. The paper will outline effective nutrient management strategies being considered in both states and will provide specific case studies for support. In addition to traditional MF, RO UV-AOP processes, advanced systems such as ion exchange polishing will also be reviewed. Additionally, potentially more cost effective approaches such as optimized biological nutrient removal systems will be explored.

For a copy of the full paper, please contact the author at rcisterna@hazenandsawyer.com

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Horizons showcases significant water, wastewater, reuse, and stormwater projects and innovations that help our clients to achieve their goals, and can help you achieve yours. Articles are written by top engineers and process group leaders, demonstrating and explaining the beneficial application of a variety of technologies and tools.

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