Wastewater System Operations
Mike Finnigan Utilities Manager
Following is a description of how wastewater is processed, treated and disposed of through the Wastewater Plant.
Influent Pump Station
- Raw wastewater (sewage) reaches the treatment facility through multiple pump stations and 72 miles of gravity sewer pipeline.
- Influent flows are first measured in a metering manhole and then flow by gravity to the influent pump station.
- The raw wastewater is then pumped to the preliminary treatment process.
- During the preliminary treatment process, macerators grind the larger particles into smaller pieces to enhance treatment and removal.
- Wastewater then flows to an aerated grit chamber where it is mixed with low pressure air to help settle out grit and other dense solids.
- The grit and solids are separated, partially dewatered, and ultimately disposed of in a landfill.
- After initial treatment, wastewater flows by gravity to the flow equalization system.
Flow Equalization System
- This system allows wastewater to be delivered to the secondary treatment process at a constant rate, which is set daily by plant operators.
- During daily peak flow periods or routine storms, wastewater is diverted to two steel equalization tanks where it is stored until it can be pumped to the secondary treatment process at a steady rate.
- During peak storms, flows are diverted further into three flow equalization ponds.
- After the storm event, the diverted water is sent back through the treatment system.
Extended Aeration Basins
- Wastewater from the flow equalization system enters the secondary treatment process in the extended aeration basins.
- Fine bubbles of air are injected through diffusers on the bottom of the tank and provide oxygen for living microorganisms that are produced and maintained as part of the activated sludge process.
- These organisms, known as "mixed liquor" break down and consume the organic material in the wastewater and build new cell mass. This cell mass is then settled in the secondary clarifiers.
- The mixed liquor created in the extended aeration basins flows into the secondary clarifiers where solids settle to the tank bottom.
- Some of this settled material is pumped back to the aeration basins as return activated sludge to maintain biological processes.
- The excess settled material is ?wasted? meaning it is pumped to aerobic digesters as waste activated sludge.
- Sludge digestion takes place in the outer chamber of two package treatment plants that previously provided all secondary treatment processes.
- Bacteria decomposes the sludge, leaving only an inert residual material.
- Decanted, digested sludge is periodically pumped to tanker trucks for land spreading in Kern County.
- The package treatment plants also serve as backup secondary treatment units when the clarifiers or aeration basins are being serviced or repaired.
- After secondary treatment, plant effluent is disinfected with sodium hypochlorite and flows to the effluent pump station.
- It is pumped to a reservoir or to four percolation basins located two miles north of the treatment plant along San Simeon Creek.
- The percolation basins create a saltwater barrier and lower the hydraulic gradient of our well field, allowing the District far greater access to upstream potable water for longer periods of time.
- In the blower building, blowers provide air for the plant's aeration and mixing for the biological processes.