National Study of Nutrient Removal and Secondary Technologies

EPA is examining efficient and cost-effective approaches for nutrient removal at publicly owned treatment works (POTW). As part of the national study, the agency conducted a survey of POTWs during 2019 to 2021.

Photo credit: Jane Thomas, Integration & Application Network,
University of Maryland Center for Environmental Science
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Study Goals

Some POTWs have added new treatment processes to remove nutrients, but these upgrades may not be affordable or necessary for all facilities. This study is helping EPA learn about other ways that POTWs are reducing their nutrient discharges, while optimizing operation and maintenance practices, and without incurring large capital expenses. The study has three main goals:

  1. Obtain nationwide data on nutrient removal.
  2. Encourage improved POTW performance with less expense.
  3. Provide a forum for stakeholders to share best practices.

Benefits to POTWs

The study will:
  • Help POTWs optimize nutrient removal by providing operation and performance information from similar types of POTWs that have already achieved successful, cost-effective approaches to nutrient removal.
  • Serve as a major new nationwide data resource on nutrient removal to help stakeholders evaluate and develop achievable nutrient reduction values.
  • Provide a rich database of nutrient removal performance for POTWs, states, academic researchers, and other interested parties.

POTWs have already seen the benefits of low-cost optimization. In 2012, the Montana Department of Environmental Quality began training POTW staff in the state on nutrient removal and optimization. POTWs whose staff fully engaged in the optimization process significantly reduced their nutrient discharges. Refer to the Fact Sheets.

Nutrient Removal Accomplished Nationwide

Initial results of the screener questionnaire help demonstrate an important aspect of the National Study: improved nutrient removal is attainable by all types of POTWs. Survey results to date show more than 1,000 POTWs with different biological treatment types (including both conventional and advanced treatment technologies) can achieve effluent total nitrogen of 8 mg/L and total phosphorus of 1 mg/L. The figure below includes those POTWs with a population served of at least 750 individuals and a design capacity flow of at least 1 million gallons per day.

Bar graph displaying initial results of POTW Nutrient Survey as of June 2020

Note: Survey respondents could select multiple biological treatment types.

Fact Sheets

Descriptions of low-cost adjustments to reduce nutrient pollutant discharges at sewage treatment plants.

Additional Resources

EPA Resources

EPA has developed many resources related to nutrient pollution, wastewater treatment, and nutrient removal in wastewater. Get started building your knowledge base with these educational websites, reports, and factsheets.

Nutrient Pollution

Wastewater Treatment

Nutrient Removal in Wastewater

Wastewater Optimization for Nutrient Removal

State and Other Government Agency Resources

Many states and other government agencies have archived helpful resources on their websites while also launching technical assistance programs for operators in their area. EPA has compiled these resources to help POTW operators across the country find information and support for plants like theirs.

  • 2011: Minnesota Pollution Control Agency (MPCA) has published an easy-to-understand comprehensive manual to Biological Nutrient Removal
  • The Tennessee Department of Environmental Conservation (TDEC) has supported many plants in improving energy efficiency and nutrient removal through the Tennessee Plant Optimization Program (TNPOP) and hosts a detailed website that provides training materials, case studies, and information on technical assistance and funding resources.
  • TDEC has also collaborated with the State of Alabama in the Advancing Energy Efficiency in Wastewater Facilities and Other Underserved Sectors in Tennessee and Alabama program and features several cases on plants in both states. Their additional resources also link to a webinar with Dr. Larry Moore, Professor of Civil Engineering at the University of Memphis, discussing his Bio-Tiger model for optimizing activated sludge wastewater treatment systems for improved energy efficiency in aeration control and reduced effluent nitrogen discharges.
  • The Ohio Environmental Protection Agency’s Compliance Assistance Unit (CAU) has compiled a brief index of technical resources related to improving nutrient removal at wastewater treatment plants.
  • The U.S. Department of Energy (DOE) has compiled the Wastewater Energy Management Toolkit, a collection of educational resources for POTW and water resource recovery facility (WRRF) operators to optimize their plant’s operations, derived from DOE's Better Buildings Sustainable Wastewater Infrastructure of the Future (SWIFt) Accelerator.

Industry Publications

Many independent wastewater organizations have developed valuable educational resources that help all wastewater operators assess and improve their plants. Read these articles to learn more about how to optimize all kinds of wastewater systems for improved nutrient removal.

Additional Information

For more information about the study, please contact Paul Shriner ([email protected]) or 202-566-1076.

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Last updated on October 7, 2024