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Arcata’s Innovative Wastewater Treatment Facility Serves as a Wildlife Sanctuary


The City of Arcata’s Marsh & Wildlife Sanctuary, located on the northern edge of Humboldt Bay, is home to the city’s innovative wastewater facility and 307-acre sanctuary that provides homes and resting places for over 300 species of birds.

Like all other wastewater treatment plants, raw sewage enters the treatment system through a typical mechanical setup where it passes through bar screens, grit separators and digestors to remove solid materials and debris.

After the clarifiers separate the sludge from the wastewater, the innovation begins! The wastewater is then pumped to the first of a series of oxidation ponds covering nearly 55 acres, where algae grows, producing oxygen which is then used by bacteria that break down the organic compounds found in human  waste. Toward the bottom of the ponds where there is less oxygen anaerobic bacteria breaks down the settled material. The water then flows through treatment wetlands, where aquatic plants, slow the flow of water and help filter the nutrients, metals and organic compounds. It is here that the algae from the oxidation ponds is removed from the water column using plants to shade and filter the algae. In these marshes aerobic and anaerobic bacteria continue to provide treatment as well.

The water is then pumped to three larger treatment marshes which are part of the Wildlife Sanctuary, where organic matter is further reduced. The water is then pumped back to the primary treatment facility for chlorination and a de-chlorination process using gas sulfur dioxide before it flows into Humboldt Bay.

Mark Andre, Arcata’ s Environmental Services Director notes that, “By integrating conventional wastewater treatment with the natural processes of constructed wetlands, Arcata has succeeded in turning wastewater into a resource, and its facility into a tourist attraction. Arcata’s system has become an international example of appropriate wastewater reuse and wetlands restoration technology.” 

The Arcata Marsh Project initially grew from an aquaculture project originally proposed in 1963, which raised salmon and trout in a mixture of seawater and wastewater started by Humboldt State University professor, Dr. George Allen. The project was under way by 1971 and saw successful return of coho salmon in Jolly Giant Creek in 1977.

The Clean Water Act and California’s Bays and Estuaries Policy prohibited discharging wastewater into enclosed bays unless “enhancement” was proven. This is where the Wildlife Sanctuary portion of the Arcata Wastewater Treatment Plant came in. In 1979, the state authorized a two-year pilot project of a 10 cell marsh to treat 10 percent of Arcata’s wastewater with plants and sunlight, with the goal of demonstrating to regulatory agencies that this concept was viable.

The California Coastal Conservancy funded the original 75 acres of constructed wetlands which was completed in 1981, the beginning of the Arcata Marsh & Wildlife Sanctuary. By 1983, the State Water Resources Control Board permitted Arcata to upgrade its wastewater treatment plant, including wetland treatment marshes.

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