Sutter Primary Treatment Facility

The Sutter Treatment Facility was built in 1919 on 38 acres of land along the Tuolumne River on Sutter Avenue. The facility began treating the City's wastewater in order to safely discharge it back into the river. Now, an average 20 million gallons a day are treated at Sutter.

This plant removes inorganic and settleable organic wastes from wastewater by separating them from the water in a large clarifier. The inorganic solids are removed and sent to the landfill for disposal. The organic solids are broken down and converted into biosolids, where they are dried and then used as fertilizer.

The remaining water is blended with cannery segregation wastewater and sent through a fixed film reactor. Bacteria within the fixed film reactor consume the dissolved solids within the water. The water then sits in treatment ponds for 65 days until it is meets effluent standards. 

Advancements over the Years

  • Prior to 1910: The City's wastewater was discharged directly into the Tuolumne River.
  • 1919: The facility began as a giant septic tank. The tank's overflow was discharged into the Tuolumne River.
  • 1928: The City purchased more acres at the facility. Oxidation and percolation beds were constructed.
  • 1930: The City replaced the septic tank with a 62-foot clarifier to better separate waste materials in the water.
  • 1937-1955: Regulatory agencies became more stringent, so the City made a number of additional improvements.
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