Conventional Treatment
Initial treatment removes over 90% of most incoming pollutants and provides a high-quality effluent for subsequent advanced waste treatment polishing steps.
- Mechanically cleaned bar screens (0.5-inch openings)
- Vortex grit chambers, 24-ft diameter
- Circular center-feed primary clarifiers with primary scum collection, 125-ft diameter
- Archimedes screw primary effluent lift pumps
- Aerobic biological selectors
- Activated sludge aeration basins
- Most basins fine-bubble diffusers
- All basins operate in nitrifying mode with active D.O. control
- Four basins have modified Ludzack–Ettinger denitrification process, can achieve 6-10 mg/L nitrate
- Multistage centrifugal blowers; total of 5700 horsepower capacity (96,200 scfm)
- Circular center-feed secondary clarifiers with draft tubes, slot-valve draft control, and biofoam collection
- 125-ft diameter
- Continuous monitoring of secondary effluent TSS and Nitrate
Chemical Advanced Treatment
UOSA uses the high-lime process to reduce phosphorus to below 0.10 mg/L. This process also serves as a barrier to viruses, captures organics leaving secondary treatment, and precipitates heavy metals.
- Silos with total storage for 240 tons of calcium oxide as pebble quicklime
- Detention-type lime slakers with lime aging tanks
- Rapid mix basins for lime slurry addition with feedback control of pH to 11
- Declining-rate flocculation basins with anionic polymer addition
- Chemical clarifiers, 125-ft circular
- First stage recarbonation to lower pH to 10 and second stage to lower pH to 7. Both stages use coarse-bubble diffusers and introduce carbon dioxide from digester boiler, carbon furnace, and pelletizer exhaust gasses, as well as purchased CO2 as necessary.
- Recarbonation clarifiers between first and second stages to collect precipitated calcium carbonate
- Gravity thickeners to concentrate chemical and recarbonation sludge
- Recessed chamber plate and frame filter presses to dewater sludge
- On-site 2 million cubic yard captive landfill for dewatered lime solids
Physical Advanced Treatment
The UOSA permit requires TSS below 1 mg/L and COD below 10 mg/L. To meet these stringent levels, multimedia depth filtration and activated carbon are used.
UOSA has two process trains, one with pressure filtration and one with gravity. The gravity system (L/2) is as follows:
- Six 100-hp vertical turbine pumps transfer effluent to filters
- Alum and/or polymer as filter aid
- Ten multimedia filters with 36-in bed of anthracite, silica, and garnet
- Continuous online turbidity measurement
- High rate backwash with air scour
- Intermediate pump station with four 120-hp submersible pumps
- Eight upflow/downflow carbon contactors with 2 million pounds of activated carbon, 22 min contact time
- Transfer facilities and blow tanks
The pressure process train is similar:
- Twelve horizontal multimedia filters
- Thirty-two upflow carbon contactors
- Eight post-filters for carbon fine removal
Activated carbon is regenerated onsite with a multi-hearth furnace
Disinfection
The final barrier to pathogens is a chlorination and dechlorination process. UOSA uses sodium hypochlorite and sodium bisulfite, and is designed to use these chemicals for breakpoint chlorination as necessary.
- Storage for 36,000 gallons of sodium hypochlorite
- Three primary disinfection chlorination pumps and three backups (52 gph)
- Three primary breakpoint chlorination pumps and three backups (1086 gph)
- Two mix chambers and four 345,000 gallon covered labyrinth contact basins
- Continuous online measurement of Total and free residual chlorine at mix chamber and after 30-minute contact time
- Bulk storage of 20,000 gallons of sodium bisulfite and transfer pumps for day tanks
- Three bisulfite feed pumps (52 gph) and two breakpoint bisulfite feed pumps (250 gph)
- Continuous online measurement of pre-dechlorination total residual for bisulfite pacing
- Continuous online measurement of post-dechlorination total residual
- Outfall to 180 million gallon final effluent reservoir
Digestion and Sludge Handling
Primary sludge and waste activated sludge are screened, digested, blended, dewatered, and ultimately dried to produce fertilizer pellets.
- Parkson strain presses remove particulates greater than 5 mm from primary sludge and WAS
- Dissolved air floatation thickeners (300 ft2 each) thicken WAS to 4-5 percent
- Three one million gallon mesophilic anaerobic digesters with IDI gas cannon mix systems
- biogas is burned for digester heating, steam for carbon regeneration and facility heating
- exhaust gasses are captured and used as primary acid to adjust pH after high-lime process
- Blending and storage tanks (260,000 gallons) with mix and transfer pumps
- Sharples DS-406 high-solids centrifuges
- Berlie/Swiss Combi pelletizer system
- rotary drum dryer
- evaporates 7200 lbs water/hour
- produces 30 tons per day of ClassA/EQ marketable pellets
- internal gas recycle for autooxidation of exhaust gasses
- 800 tons of pellet storage
- RDP lime stabilization system as backup
- Two stage odor control system (caustic/acid) wet chemical scrubbers
