Prior Awards

Work previously funded by cooperative agreements with EPA Region 10.


Nitrogen - A Problem for Puget Sound

Sewage typically contains high levels of nitrogen. Even with new technologies, on-site sewage (septic) treatment systems generally have limited ability for removing nitrogen in wastewater. This can result in increased nitrate concentrations, or "nitrogen loading" in ground and surface water. And high nitrate levels in drinking water can affect human health.

Nitrogen loading is an environmental concern in the Lower Hood Canal and other regions of the Puget Sound. Excess nitrogen fuels the growth of algae. As algae dies and decays, it consumes oxygen. This process contributes to depleted dissolved oxygen conditions in Puget Sound and can harm aquatic life.

For more information see our fact sheet How Nitrogen from Septic Systems Can Harm Water Quality (PDF).

Nitrogen Removal Verification

An objective of the denitrification project was to expand reliable and affordable nitrogen removal options for septic treatment systems in Washington State. Our Wastewater Management Section partnered with the University of Washington's Department of Civil and Environmental Engineering to evaluate various septic treatment systems for their nitrogen removal abilities. See our project overview (PDF).

Three public domain, cost-effective septic treatment technologies were selected for testing. These technologies have been successful in other parts of the United States in removing high amounts of nitrogen from sewage. Because denitrification processes are temperature dependent, we didn't know if they would be effective in Washington's climate.

The three systems were built, tested, and evaluated over a one-year period using the EPA Environmental Technology Verification (ETV) protocol for nutrient reduction. A stakeholder advisory committee was formed to help in the evaluation process. We compiled ETV test results for each system and wrote final reports based on those results. The systems evaluated were:

Vegetated recirculating gravel filter (VGRF) that is comparable to a recirculating vertical flow constructed wetland.

Passive two stage nitrification and denitrification system that includes a recirculating gravel filter followed by a vegetated denitrifying woodchip bed (RGFW).

Enhanced recirculating gravel filter (ERGF) that is also designed to maximize nitrogen removal efficiencies.

Technology Standards Development

The environmental technology verification results show both the vegetated recirculating gravel filter and the recirculating gravel filter with the woodchip bed systems are reliable and effective in removing nitrogen from wastewater. We are developing standards and guidance for the use of these two treatment technologies as supported by their ETV results.

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Pathogens Prevention, Reduction, and Control – Lead Organization


The Department of Health's Office of Environmental Health and Safety managed a pathogen reduction cooperative agreement from 2010- 2017 in the Puget Sound region. The funds focused on preventing and reducing pathogen pollution in Puget Sound through management of human and animal wastes.

The EPA funded Pathogens Lead Organization work assisted in making gains towards  the Puget Sound Shellfish Beds vital sign—upgrading 10,800 acres of harvestable shellfish beds by 2020—by improving water quality. It worked to advance the goal of a “swimmable, diggable, fishable” Puget Sound and aligned with the Washington State Shellfish Initiative. This work helped to lay a foundation for the Shellfish Strategic Initiative in the years to come.


EPA provided over 15 million dollars to manage pathogen pollution for the following project types:

  • On-site Sewage System Management – Puget Sound health jurisdictions worked to document and inspect onsite sewage systemsand to fix failing on-site sewage systems.  Regional projects helped local communities establish sustainable funding for on-site sewage system management and septic repairs in some instances.
  • Pollution Identification and Correction (PIC) – Local communities monitored  water quality to identify pollution sources and providing outreach, technical assistance, incentives and enforcement to reduce pollution from onsite sewage systems and farms.
  • BEACH Program – Monitored and notified the public about bacterial pollution at recreational marine water beaches.
  • Livestock Management – Worked  with farmers to install fencing, feeding and watering facilities to keep manure out of streams. Conducted site visits and offered technical and financial assistance to reduce pollution from farms by using best management practices.
  • Vessel Sewage – Explored designation of Puget Sound as a No Discharge Zone which prohibit boats from dumping sewage.  Installed pump out facilities and promoted their use.
  • Research – Researched new technologies to reduce pollution and pathogens.
  • Data Management and Reporting – Improved our tracking of pathogens and notification of the public about shellfish closures and biotoxin threats through updates of our data management and reporting system.
  • Investment Strategy – Developed an investment strategy to ensure coordination with the Puget Sound Action Agenda.


Megan Schell,

On-site Sewage System Ultraviolet Disinfection Study

Effective on-site sewage treatment reduces the risk of disease transmission and human exposure to pathogens, which can occur through drinking water, surface water, and shellfish bed contamination. The ability of the soil to reduce pathogens in on-site sewage system effluent is impacted by a variety of factors such as soil texture and structure, depth and distance between point of discharge, and the nearest ground or surface water requiring protection. At some sites, the treatment capacity of soil or proximity of the soil dispersal component is insufficient. Disinfecting effluent before soil dispersal is a way to rectify this shortcoming.

Ultraviolet (UV) disinfection is the most commonly used disinfection method in Washington State and more than 6,000 UV disinfection (UVD) units are currently in use. Many members of the on-site wastewater industry and local health jurisdictions have expressed concerns that UVD units are ineffective and not functioning reliably under field conditions. Ongoing operational and installation problems and high maintenance costs associated with UVD units have been reported, raising questions about the need for their use, and whether costs outweigh the benefits of UV disinfection in the field.

Field Effectiveness of UVD Units in On-Site Sewage Treatment

The purpose of this study was to evaluate the effectiveness and reliability of UVD units in the field, and to determine if additional management measures are necessary to assure UVD unit performance on sites that are highly susceptible to microbial pollution. The evaluation work was carried out by staff within the Wastewater Management Section of the Washington State Department of Health in partnership with Tacoma-Pierce County Health Department, Thurston County Public Health and Social Services Department, and University of Washington.

Approximately one hundred on-site sewage systems with permitted UVD units were evaluated in Thurston and Pierce Counties for indicators of proper installation, maintenance, electrical, and physical status. Effluent samples from twenty-two UVD units were also collected and analyzed for microbial and physical quality in Thurston County. We compiled results from all of the systems evaluated and wrote a final report based on those results.

Final Report


Standard Operating Procedures


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Contact Meagan Jackson at to access the Master's Thesis.