Pritchett Water Reclamation Facility (WRF) Project

New Arbennie Pritchett WRF Treatment Process

The new WRF will will be designed to treat an influent average daily flow of 10 mgd and a peak hourly flow of 25 mgd. Provisions for future expansion to 15 mgd and 37.5 mgd respectively, also will be considered during the design. The new WRF will consist of four major process areas and the support facilities as described below:

• Pretreatment Process
• Biological Treatment Process
• Effluent Management
• Biosolids Management
• Support Facilities

Pretreatment Process

The pretreatment processes are intended to provide gross removal of large solids and grit to protect downstream equipment. Pretreatment process components consist influent flow monitoring, influent composite sampling, mechanical and manual screening, screenings washing and dewatering equipment, grit removal and handling equipment, odor control, and septage receiving equipment. The pretreatment facilities are designed to provide complete redundancy and have the hydraulic capacity to meet the future peak hourly flow of 37.5 mgd.

Biological treatment process

The biological treatment process is intended to remove or reduce organic constituents, nutrients, and suspended solids from the wastewater. Treatment include activated sludge bioreactors, secondary clarification, and return activated sludge and waste activated sludge (RAS/WAS) pumping. The activated sludge bioreactor system shall be furnished to provide necessary biological treatment of the wastewater to meet permit conditions, shall be designed to reduce carbonaceous biochemical oxygen demand (CBOD), ammonia, nitrite, and nitrate to the prescribed effluent treatment levels, when this process is followed by secondary clarification.

The biological treatment basins shall be configured with influent entering an anoxic zone to provide both anoxic selector and denitrification when combined with an internal mixed liquor suspended solids (MLSS) followed by an aerobic zone. The MLSS from the biological treatment basins shall flow to the secondary clarifiers. The design of secondary clarifiers shall take into account the biological process that precedes it and the RAS and WAS. A RAS pumping system shall be provided to return mixed liquor solids settled in the secondary clarifiers to the activated sludge biological treatment basins. The RAS shall be pumped back to the head of the aeration basins, before the first anoxic zone of the basins. The WAS pumping system shall remove the portion of activated sludge solids from the secondary clarifiers to be wasted from the process.

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Effluent Management

Effluent management includes ultraviolet disinfection and effluent pumping and an in-plant reclaimed water system for process operations and landscape irrigation. The effluent management structure includes the new Ultraviolet (UV) light disinfection system, as well as the pumping wetwell for the effluent and in-plant water pumps. The structure shall be designed to accommodate the future peak hourly flow of 37.5 mgd. The new UV disinfection system equipment shall be provided to accomplish disinfection of the clarifier effluent to limits prescribed in the permit. The UV system shall implement low pressure high intensity lamps arranged in open channels where the water shall flow by gravity continuously. Lamp arrangements within the channel will be vertically configured and shall have the capacity to treat a peak hourly flow of 25 mgd. The new effluent pumps shall consist of a triplex pumping arrangement with vertical turbine pumps designed to pump the peak hourly flow of 25 mgd to the new RIBs.

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Biosolids Management

Biosolids management facilities are intended to prepare the sludge for land disposal. The processes include sludge thickening, aerated sludge digestion, sludge dewatering, and dewatered sludge loading for offsite disposal. A rotary drum thickener and polymer addition system will be provided to thicken the waste sludge to a concentration of about 5 percent before it is discharged into the digester. Two pre-stressed concrete aerobic digester tanks shall be provided to treat the biosolids to meet the Class B standards for land application. The digested sludge shall be conveyed to a centrifuge for dewatering to a concentration of greater than 18 percent. Polymer shall be applied to enhance the dewatering process. The dewatered sludge shall be discharged from the centrifuge directly to the storage bins. The biosolids management unit processes are designed based on the average daily flow of 10 mgd and the assumption that the sludge dewatering units will operate seven hours per day, five days per week.

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Support Facilities

Support facilities include a new administration/laboratory building, maintenance building, and other ancillary electrical buildings and facilities, including standby diesel generators design to power the necessary plant operations during extended power outages.

» PDF of WRF Rendering

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