How It Works

Raw sewage from the south and north mainlines enter the WWTP headwork’s and flows through a ¼ inch opening automatic bar screen provided by Headworks, and grit removal system from Smith and Loveless, which discharges into the influent pump station wetwell.

Wastewater is then pumped to the WWTP biological treatment tank provided by Aero-Mod Inc. At the biological treatment tank, the wastewater splits into two treatment trains at the selector tank; each train provides two-stage aeration and biological denitrification. There are two secondary clarifiers where the activated sludge biomass is separated from the secondary effluent. Secondary effluent is chlorinated then passes through the chlorine contact basin prior to dechlorination before either discharge to the Eel River (October-May) or the flood irrigation fields (May- October).

Aerial photo of wastewater facility

The solids removed from the wastewater are stored and thickened in two aerated digesters and subsequently dewatered with an Aero-Mod Tritan belt filter press.

Wastewater machinery

Wastewater machinery

The dewatered bio solids are processed through an indirect sludge dryer made by Therma-Flite, which produces a Class A bio solids that the City is able to give away to residents as a soil amendment.  If any residents would like to pick up any of the bio solids to use for their yards or gardens please call the treatment plant at 707-764-5754 to arrange a time.


Pile of dewatered bio solids