Sonoma Valley Treatment Plant Detailed Virtual Tour

This website was created as part of the application for the 2001 CWEA plant of the year award. It is mainly comprised of this basic tour page and a detailed tour page. A dye testing page was also included since clarifier dye testing was performed on the day that the bulk of these pictures were taken (November 1, 2001). These pages may be slow to load due to the number of images.

Operations building (control room, lab, chemical storage)

The Operations building includes the control room, lab, and chemical storage and feed.

The Headworks is comprised of flow metering, screening of large debris from the sewage, screenings washing, and pumping of influent sewage.

A new Pista grit chamber removes heavy inorganic grit such as sand, rock, and eggshell.

Following preliminary treatment, the raw sewage is blended with Return Activated Sludge (RAS) and introduced into Complete Mix aeration basins. The blend of RAS and raw sewage is known as Mixed Liquor. The RAS is a concentrated microbial mass, which is mostly aerobic bacteria. Under aeration the bacteria consume the sewage pollutants, yielding more microbes and clean water.

Following aeration, the Mixed Liquor is introduced into circular secondary clarifiers. Within the clarifiers the micobial mass settles to the floor and is pumped back to aeration to consume more food (sewage) while the clean water continually overflows from the clarifier surface.

Following Clarification, chlorine solution is injected into the secondary effluent, which is then introduced into the Chlorine Contact Chambers. The contact chambers provide the time necessary for the chlorine to do a good job of disinfecting the water.

Sulfur dioxide solution is used to dechlorinate the final effluent, removing the remaining residual chlorine.

Final effluent is used to enhance wetland areas in the fall (above).

From May 1 to October 31 final effluent is used for dairy crop and vineyard irrigation.

From November 1 to April 31 final effluent is discharged to Schell Slough (a tidal tributary of San Pablo Bay).