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National Study of Nutrient Removal and Secondary Technologies

EPA is conducting a national study focused on nutrient removal and the technologies employed to achieve that removal at municipal wastewater treatment plants, also called publicly owned treatment worksHelppublicly owned treatment worksA waste-treatment works owned by a state, unit of local government, or a tribal entity, usually designed to treat domestic wastewaters. (POTWs).


""Nutrient pollution is one of America’s most widespread, costly and challenging environmental problems impacting water quality. Excessive nitrogen and phosphorus in our waters can lead to a variety of problems including eutrophication and harmful algal blooms, with impacts to drinking water, recreation and aquatic life. A wide range of human activities can contribute to nutrient pollution including stormwater runoff, agriculture, and wastewater discharges.

""Many POTWs have added treatment processes for extensive nutrient removal, but these upgrades are not affordable or necessary for all facilities. Some POTWs have reduced their nutrient discharges by optimizing operation and maintenance practices without incurring large capital expenses.

Improving Nutrient Removal at POTWs

Currently, there are no comprehensive nationwide data on nutrient discharges and removal at POTWs. EPA and POTWs can use the information gathered from this study to learn about low-cost, effective solutions for reducing nutrient discharges.

Study Goals

  1. Obtain nationwide data on nutrient removal to help set more realistic and achievable nutrient reduction targets.
  2. Encourage improved POTW performance with less expense.
  3. Provide a forum for stakeholders to share best practices.

Study Design

""The full study is designed with multiple phases over the course of four to five years, allowing for interactions with stakeholders and experts in each phase. Conventional secondary treatment plants are the technical focus of the National Study.

The first phase of the study is collecting basic information from all facilities nationwide using an interactive, online screening questionnaire. The screener will collect data on technology in place and typical operations challenges. The questionnaire is tailored to minimize the number of questions, and reduce burdens on facilities that have limited staff available to respond to the survey.

Following the screening questionnaire, EPA plans to select a sample of facilities for further study, through a more detailed questionnaire, and influent/effluent sampling.

The screener questionnaire

Incorporating stakeholder comments, EPA has designed the questionnaire to minimize burden and time required to complete.

Questions include those necessary to identify and stratify the universe of POTWs and, within that population, the secondary treatment POTWs not designed specifically to remove nitrogen and phosphorus. The survey makes use of multiple choice and “yes/no” questions, with drop-down menus and checkboxes from which respondents can choose the appropriate answer.

The questionnaire is designed to reduce burden by asking fewer questions for POTWs serving small populations and having no industrial inputs. EPA is not including open-ended questions in the questionnaire which would likely be unwieldy, due to the number and expected variation of responses.

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Benefits to POTWs

""The multi-phase 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.

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Additional Resources

Additional Information

For more information on the study, please send inquiries (

Photo credits:
Jane Thomas, Integration and Application Network, University of Maryland Center for Environmental Science.Exit

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