The City of West Sacramento Wastewater Treatment Plant was first built in 1948. The Plant has gone through two expansions; one in 1977 and one in 1988 along with one major improvement project during the early 90's. The plant uses a secondary treatment activated sludge process with an anoxic selector. The average daily flow is 5.5 MGD (Million Gallons per Day). Below is a basic description of the treatment process. As you can see, as much energy as possible is recycled to power other areas of the treatment process.

Treatment Process

The initial step of the treatment process is to remove large, non-organic solids with a fine bar screen. The following process, called primary treatment, slows the sewage flow down to allow large, heavier solid material to settle out to the bottom of the tank. From this point, the flow goes into the aeration basins where soluble sewage is transferred into biological cell growth for further processing. The flow then enters into our secondary clarifiers where the biological cell growth settles to the bottom of the tank. The clear water, left on top, travels into the chlorine contact chambers where we add chlorine to kill any harmful bacteria.

The solids that are captured in the primaries are pumped into large round tanks called digesters. These tanks are heated and mixed, the by-product is a usable gas called methane. We capture this gas and burn it to use as a fuel source in one of our two 325hp engines. These engines turn large fan blowers that provide air for the aeration basins.

After treatment in the digesters, the "digested" sludge is pumped to one of two belt presses. The solids that are pumped to the presses average about 3 % solids. After we press the water out of the sludge, the formed solid, known as cake, averages about 17% solids. These solids are then trucked off site for land application in San Joaquin County.