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Wastewater Division - Treatment Plant 3

Treatment Plant 3

Treatment Plant 3 Photos:

Wastewater Treatment Plant 3
Septage and Grease Receiving Station: The septage hauled to the plant is first processed by the septage processing units, and then transferred to a storage tank from where the septage is pumped to the headworks through the plant drain system. The septage pumping system is designed to deliver the septage at a controlled rate to avoid shock loading (momentary overloading) to the plants wastewater treatment process. Grease that is delivered to the treatment plant is collected into an aboveground fiberglass storage tank. From this tank, the grease is pumped to the anaerobic sludge digesters via the plant’s sludge and scum piping system. The purpose of adding grease to the digesters is to augment the production of digester gas.
Wastewater Treatment Plant 3
Headworks: Raw wastewater (called influent) from the sewer system enters the treatment plant at the headworks. Here, the wastewater passes through three mechanical bar screens that remove large debris, rags, sticks or other objects that may damage equipment used in the treatment process. Wastewater is then pumped to the aerated grit chamber which removes sand, gravel and metallic objects. The removals of solids improve treatment efficiency and help protect the equipment against excessive wear.
Wastewater Treatment Plant 3
Primary Clarifiers: The wastewater, after screening and grit removal, is distributed to eight primary clarifiers. The purpose of the primary clarification is to separate settleable solids from the wastewater by gravity as solids heavier than the liquid settle down (primary sludge) and are collected at the bottom of the clarifiers. Also, the materials lighter than the liquid will float on the surface (scum) and will be skimmed off. The effluent from these clarifiers is collected into Flow Junction Box and delivered to the plants secondary process. The sludge scraped from the clarifier floor is conveyed to a sludge hopper located at the center of each clarifier. The primary sludge is pumped to anaerobic digesters for further breakdown and digestion.
Wastewater Treatment Plant 3
Activated Sludge Process (Aeration Basins): The flow from primary clarifiers effluent is conveyed to the flow junction box and from there to the aeration basins. The purpose of the aeration basins is to support biological activities responsible for removing BOD (Biochemical Oxygen Demand) and nitrogen contents of the wastewater, and, also, producing flocs that settle well within the secondary clarifiers, thus removing suspended solids and BOD.
Wastewater Treatment Plant 3
Secondary Clarifiers: The purpose of the secondary clarifiers it to separate the solids from the liquid by gravity as the solids heavier than the liquid settle down (sludge) and are collected at the bottom of the clarifiers. Also, the materials lighter than the liquid will float on the surface (scum) and will be skimmed off. Thus, clear water leaves the secondary clarifiers. Secondary clarifiers operate similar to primary clarifiers, the major difference being the lower density of the secondary sludge compared to that of the primary sludge.
Wastewater Treatment Plant 3
Percolation Ponds: The plant has ponds for the disposal of treated secondary effluent and for the purpose of temporary storage.
Wastewater Treatment Plant 3
Tertiary Treatment Process: Filtration is a tertiary treatment process typically adopted to remove organic and inorganic colloidal and suspended solids. The filtered wastewater is disinfected through a chlorination system to reduce the concentration of the total coliform bacteria in the plant effluent. Filtered wastewater is sent to a mixing chamber where sodium hypochlorite solution is injected and then conveyed to two storage tanks. Disinfected water flows out of the chlorine contact tanks into the wet well of the recycled water pump station.
Wastewater Treatment Plant 3
Recycled Water Storage & Distribution System: A portion of the recycled water is used as seal water for various pumps within the treatment plant, and for irrigation within the plant boundary. In addition, it will be used to irrigate our new soccer park (Sports Village) south of the plant. Recycled water is the result of the tertiary treatment and is stored in our storage reservoir.
Wastewater Treatment Plant 3
Dissolved Air Flotation (DAF) Sludge Thickeners:  Solids separation using dissolved air flotation method is based on variation of the solubility of air in the water .The objective of flotation thickening is to separate solids from the liquid phase in an upward direction by attaching air bubbles to particles of suspended solids. Floatable solids are collected in the float box and settled solids are raked from the bottom of the tank and are combined and transferred to a valve box were its thickened and distributed to the digesters.
Wastewater Treatment Plant 3
Anaerobic Digesters: Collected sludge is pumped into heated tanks (Digesters). Anaerobic  (absence of oxygen) bacteria thrive in the digesters, and convert raw sewage sludge to an inert material (Digested sludge), methane gas and carbon dioxide. The anaerobic digestion process produces gas (methane) as a byproduct which we use for heating digesters and generation of electrical power for in-the plant use.
Wastewater Treatment Plant 3
Sludge Dewatering: The digested sludge from the digesters is transferred to the centrifuges in the dewatering building by the centrifuge feed pumps. The centrifuges separate the digested sludge solids (cake) from the liquid (centrate). Sludge cake is discharged to a system of collection screw conveyers for transfer to sludge hauling trucks. The sludge cake is then hauled away for off-site disposal.
Wastewater Treatment Plant 3
Digester Gas Treatment & Power (Cogeneration): The cogeneration system is used to recover the energy available from the digester gas for plant use. Recovery of the energy from the digester gas is accomplished by feeding the gas to two engine-generators for electrical power production and generation of hot water for digester heating through recovery of a portion of the waste heat from the power generation equipment.
Wastewater Treatment Plant 3
Odor Control: As part of our odor control biofilters are utilized which have naturally occurring microorganisms to oxidize the odorous compounds from the foul air being treated before releasing it to the atmosphere.
Wastewater Treatment Plant 3

Electrical Power System Description: Electricity is required on all process areas in the plant for power, lighting, electrical instrumentation, and control. PG&E is providing one 12KV primary power service that connects to the Main 12KV Switchgear M. This switchgear consists of the main power circuit breaker and feeder circuit breakers, the utility revenue metering section potential and current transformers for protective devices/relays and control transformer for the 120 VAC load requirements. The main switchgear is equipped with substation batteries and charger for the operation and control of all the power circuit breakers and protective relays.

Wastewater Treatment Plant 3
Supervisory Control Data Acquisition: The Supervisory Control and Data Acquisition (SCADA) system monitors and controls the Wastewater Treatment Plant.
Wastewater Treatment Plant 3
Solar Panels: The solar panel energy field is has 1 mw of power and 2 cogen engines 848 kw each to support the plant through peak electrical demand and to help reduce our utility bill.