Santa Clara Waste Water Treatment

Santa Clara Waste Water Treatment

Every day, 365 days a year, the San José-Santa Clara Regional Wastewater Facility cleans Silicon Valley’s wastewater to very high national standards, protecting public health and the environment, and supporting the economy. Using a process that simulates the way nature cleans water, the Facility treats an average of 110 million gallons of wastewater per day (mgd), with a capacity of up to 167 mgd.

After wastewater enters the San José-Santa Clara Regional Wastewater Facility (Facility), it undergoes a three-step treatment process to remove solids, pollutants, and pathogenic bacteria. Machinery and gravity separate solids from the wastewater. Added bacteria clean the water pollutants before the flow enters the advanced filter process. The treatment process produces water that is 99% purified and is subsequently discharged into the Bay.

Pretreatment

Large bar screens remove rags, sticks, rocks, and other debris that could otherwise clog machinery. The debris is then transported to the landfill.

Primary Treatment

This 24-hour physical process removes about 50 percent of wastewater contaminants. In large tanks, the flow is slowed to allow gravity to separate large particles. This process mimics the natural processes of creeks and rivers, where sediments settle to the bottom. Fiberglass bars, or flights, move across the tank surface to skim off fats, oils, and grease. Flights gradually rotate from the top to the bottom and the settled solid particles are moved into the digesters.

Digesters: The pollutants and solid material removed during the three treatment steps are separated from the liquid flows in digester tanks. It takes 25 to 30 days for anaerobic bacteria to stabilize unwanted material and reduce the pathogens and other disease-causing organisms in the solids. Anaerobic bacteria operate best without oxygen and at about 98 degrees. Digesters produce methane gas, which meets 35% of the Facility's energy needs.

Secondary Treatment

Aeration:  Aeration is a biological process that produces 95% clean water by pumping air into the flow. The oxygen-rich (aerobic) environment nurtures the growth of naturally-occurring aerobic bacteria.

Clarifiers: After aeration, the flow is piped into clarifiers where the aerobic bacteria settle to the bottom. Treated water remains in the clarifiers for one to three hours. Mechanical arms move slowly around the tank to collect scum and bacteria for the digesters. Some bacteria are then sent back to the aeration tanks to repeat the process.

Tertiary Treatment

Tertiary treatment is the third and final process. During tertiary treatment, wastewater flows through several filter beds composed of gravel, sand and anthracite coal. This step is also known as "advanced" treatment because few communities undertake it. The three treatment plants located in South San Francisco Bay require tertiary treatment because their water discharges into shallow waters with little tidal action.

 The "advanced" treatment is needed to ensure that our water meets state and federal water quality regulations. Water is 99% pure after tertiary treatment. Following filtration, liquid hypochlorite solution is used to purify the water further. Before being discharged into the Bay, a second chemical is added to neutralize the chlorine, which could otherwise harm aquatic life.

After tertiary treatment, about 90% of the treated water is piped to the outfall channel. From here, it flows to Artesian Slough, through Coyote Creek, and eventually into the Bay. Many birds and fish are found at the outfall channel, including stripers, black bass, and salmon.

The remaining 10% of the treated water is sent to South Bay Water Recycling and used to irrigate food crops, parks, schools, golf courses, street medians, and business park landscaping.