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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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Screw pumps draw wastewater into the grit room for the initial filtration.
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Internal grooves in the screw pump gather water and push it into the facility.
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The grit chamber provides the first level of filtration by passing the wastewater through a fine grate, which removes large debris and allows inorganic solids to settle at the bottom for extraction.
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The wastewater is then directed to the two million-gallon clarifier, where heavy solids sink and lighter contaminants float. Both are removed via a skimming arm.
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An empty clarifier.
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Twin primary digesters act like giant stomachs to break down solid waste into methane gas and sludge.
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The polishing digester further breaks down the sludge produced by the primary digesters and deposits the result into drying beds. The sludge dries and turns into fertilizer.
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Inside the digesters, the sludge is kept in a constant state of motion to avoid creating a toxic environment for the microorganisms.
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Pumps then transport the treated wastewater about 6 miles through underground pipes to the Jennings Secondary/Tertiary Plant.