The final phase of Westside Wastewater Treatment Plant's upgrade was completed in 2018. The 3-phase upgrade not only increased the permitted treatment capacity of the plant from 6.2 MGD to 8.2 MGD, but it also upgraded the plant from an Activated Sludge treatment Facility to a 5-Stage Biological Nutrient Removal (BNR) Facility.
The Treatment Process
The purpose of the preliminary treatment process is to remove large objects and grit thereby preventing possible damage to the downstream treatment units. The process consists of 1 mechanical coarse bar screen and 2 mechanical fine bar screens that remove objects such as rags, sticks, and other large items from eh raw wastewater. After the screening process, the wastewater goes through the grit removal facilities where 2 stirred vortex grit collectors remove sand and gravel.
Primary clarification includes 2 primary clarifiers which reduce grease, solids, and some organics from the influent wastewater by settling. The settled solids (sludge) are scraped to a hopper in the center of the clarifier by a rotating scraper mechanism and pumped to the sludge holding tanks where they e later treated by the Solids Handling Facility.
5-Stage Biological Nutrient Removal (BNR)
The 5-Stage BNR process relies on microorganisms the BNR tanks' mixed liquor solids for removal of organic material, phosphorus, and nitrogen from the primary effluent wastewater. The 5-stages consist of an anaerobic zone, anoxic zone 1, aeration zone, anoxic zone 2, and reaeration. Each zone supports certain microorganisms in the mixed liquor which enables the treatment of the wastewater from primary clarification. The BNR process requires careful operator control to ensure that satisfactory conditions are maintained for best treatment performance.
Final clarification consists of 3 final clarifiers, each with a sludge removal mechanism. Flow leaves the BNR tanks and enters the final clarifiers through a center feed well and flows out radially towards the periphery. Solids within the process settle and are then collected from the clarifier by rotating arms that are just above the clarifier floor. Three return sludge pumps, pump the solids back into the BNR process or it is wasted to the Solids Handling Facility by 2 waste sludge pumps. The effluent flow from the final clarifiers is routed through 5 filters to remove the small number of solids that remain.
Ultraviolet (UV) Disinfecting
The UV process consists of 2 channels each with 2 banks of 40 UV lamps. The effluent flow is disinfected by the UV lamps as it leaves the plant and is discharged into Rich Fork Creek in the Yadkin-Pee Dee River Basin.