An environmental organization announced plans Tuesday to build a large freshwater hatchery at Bartram’s Garden in Philadelphia capable of producing 500,000 mussels a year as part of an effort to help filter and purify water in the Delaware, Schuylkill, and Susquehanna Rivers.

The Partnership for the Delaware Estuary says it has signed a $7.9 million funding agreement with the Pennsylvania Infrastructure Investment Authority (PENNVEST) to plan, design, and begin building the hatchery and mussel program starting in 2020. The goal is to begin producing mussels at the Southwest Philadelphia location by 2023.

The Partnership for the Delaware Estuary said the facility “may be the first of its kind in the world — a large-scale freshwater mussel hatchery ultimately designed for the promotion of clean water.”

Native mussels have been in decline for years in the waterways. Mussels function as mini-wastewater treatment plants, with one capable of filtering fine pollutants from 10 gallons of water a day.

“The hatchery will allow us to really see what mussels can do to make our rivers and streams healthier,” Jennifer Adkins, executive director of the Partnership for the Delaware Estuary, said in a statement. “PENNVEST’s willingness to invest in such an innovative new approach to improving water quality is outstanding.”

The Partnership for the Delaware Estuary is a nonprofit group that collaborates with other organizations to help protect the Delaware Estuary, where fresh water from the Delaware River mixes with salt water from the Atlantic Ocean. A clean Delaware River is essential to its mission.

PENNVEST is a state agency that funds sewer, storm water, and drinking water projects.

The baby mussels produced in the hatchery will be reared in nursery ponds and then moved to either the rivers or their tributaries.

The hatchery itself will cost between $5 million and $6 million, and should be built and operating within the first five years of what’s expected to be an eight-year project. The remainder of the money will be used to build offsite facilities to rear mussels after they come out of the hatchery.

“A healthy and robust bed of freshwater mussels is something to behold, and we’re now beginning to understand that natural mussel beds provide important benefits to ecosystems, fisheries, and people — similar to the highly touted benefits that oyster reefs play in saltwater bays,” said Danielle Kreeger, the partnership’s science director.

Kreeger said that although her group’s focus is the Delaware, she felt it was important to be able to supply mussels to the Susquehanna, a source of pollution of the Chesapeake Bay.

Bartram’s Garden and the Philadelphia Water Department will also help with the project.

“In addition to the impact on our watershed, this is a wonderful opportunity to inspire the thousands of students who visit Bartram’s Garden each year,” said the garden’s executive director, Maitreyi Roy. “Connecting our local youth with the daily work of scientific research and watershed health will allow them to imagine their own connection to the river and its future.”

The new hatchery will build on the work being done at an existing hatchery exhibit at the Fairmount Water Works. Both facilities will work to advance goals of the Aquatic Research and Restoration Center, a collaboration among the Water Department, Philadelphia Department of Parks and Recreation, Drexel University College of Arts and Sciences, the Academy of Natural Sciences of Drexel University, the Independence Seaport Museum, and Bartram’s Garden.

The hatchery at the Water Works produces 15,000 to 20,000 mussels for the Delaware River.