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Environmental Services

working for clean rivers

Phone: 503-823-7740

Fax: 503-823-6995

1120 SW 5th Avenue, Room 1000, Portland, OR 97204

More Contact Info

Design Criteria and Capacities of Processes

Abbreviations and Terms

  • mgd = million gallons per day (flow)
  • mg = million gallons (volume)
  • ppd = pounds per day
  • gsfd = gallons per square foot per day
  • rpm = revolutions per minute
  • phm = pound per hour per meter
  • hp = horsepower
  • RAS = return activated sludge
  • mg/L = milligrams per liter
  • mL/g = milliliters per gram
  • BOD5 = biochemical oxygen demand in 5 day test
  • SVI = sludge volume index

 

Parameter

Value

Service Population 587,865
Number of Employees 153
Annual Operating Cost 13,900,000

Flow

 
     Dry Weather Flow 100 to 130 mgd
     Wet Weather Capacity 380 to 450 mgd

Design BOD5 load

 
     Average dry weather month 159,294 ppd
     Maximum dry weather month 241,860 ppd

Design effluent requirements

 
     Maximum monthly average total suspended solids 30 mg/L 
     Maximum monthly average BOD5 30 mg/L

Influent pumps (WWIPS)

 
     Capacity 150 mgd
     Number 9
     Type 6 submersible and 3 dry pit submersible
     Speed 6 variable speed drive and 3 constant speed
     Capacity

3 at 10 mgd

3 at 16 mgd

3 at 25 mgd

     hp 

3 at 90

3 at 150

3 at 215

Influent pumps (headworks pumps)

 
     Capacity 300 mgd
     Number 6
     Type centrifugal
     Speed variable
     Capacity

2 at 40 mdg

4 at 75 mgd

     hp

2 at 250

4 at 450

Preliminary treatment

 
Headworks  
     Capacity 300 mgd
     Debris Screening Type Screen and Rake
          Number 5
          Spacing clearance 5/8 inch
     Grit basins  
          Number 6
          Type mechanically-induced vortex
          Size 24-foot diameter
          Efficiency 85 percent of 100 mesh at 130 mgd
Wet Weather Screening Facility  
     Capacity 150 mgd
     Debris Screening Type Rotating Filter Screen
          Number 4
          Spacing clearance 6mm (1/4") perforated panels w/tines

Primary treatment

 
     Primary clarifiers (dry weather)  
     Capacity 160 mgd (40 MGD per clarifier)
          Number 4
          Size 250 feet long by 60 feet wide by 10 to 14 feet deep
          Overflow rate 2,666 gsfd at 120 mgd
     Primary clarifiers (wet weather)  
     Capacity 330 mgd
          Number 8
          Size 225 feet long by 58 feet wide by 10 feet deep
          Overflow rates (one unit out of service)

3,284 gsfd at peak flow

2,880 gsfd at 300 mgd

Secondary Treatment

 
Aeration basins  
     Capacity 100 to 130 mgd
     Number 8
     Size 381 feet long by 40 feet wide by 17 feet deep
     Volume, each 1.8225 MG
     Capacity, each 20.0 mgd at a SVI of 80 mL/g
     Design organic loadings  
          Instantaneous peak 120,000 BOD5 and 17,800 ppd ammonia
          Diurnal peak 90,000 BOD5 and 13,350 ppd ammonia 
          Minimum 20,000 BOD5 and 3,000 ppd ammonia
     Detention time 3.5 hours at 100 mgd and 60 percent RAS
Aeration equipment type fine-bubble diffusers
Mixer type (anoxic zone) floating mechanical mixers

Secondary clarifiers

 
     Capacity 120 mgd
     Number 8
     Type square, peripheral-feed  
     Size 125 feet square
     Sidewater depth 12.5 feet
     Surface overlow rate 800 gsfd at 100 mgd
          Solids loading rate 32.4 ppd per square foot
          Detention time 2.79 hours at 100 mgd
          Sludge removal revolving suction arm

Sludge recirculaton

 
     Number of pumps, each clarifier 2
     Type Variable speeds
     Combined capacity 62.5 mgd

Disinfection

 
     Capacity  450 mgd total
     Type sodium hypochlorite
     Control residually paced, flow-paced or compound loop
     Storage 75,000 gallons
     Metering pumps 4 dry weather and 4 wet weather
     Reactor chlorine contact pipes
     Rated capacity, each 90 mgd

Water Reuse

 
     Supply pumps 2 @ 4 mgd each
     Microscreens 2 (11 micron screen media opening)
          Capacity, each 3 mgd
     Discharge pumps 2 @ 4 mgd each

Gravity belt thickening of secondary sludge for digestion (TWAS)

 
     Number 3
     Width, each, meters 3
     Feed flow rate, each, gpm 900

Anaerobic digesters

 
     Number 10
     Diameter, feet

4 AT 90

4 at 105

2 at 104

     Sidewater depth, feet

4 at 25.3

4 at 37

2 at 40

     Effective volume, each, cubic feet

4 at 160,000

4 at 320,000

2 at 340,000

Triangle Lake sludge lagoon

 
     Area, acres 36
     Dredge capacity, gpm 800

Mechanical dewatering

 
     Belt Filter Press  
          Number 4
          Belt width, meters 2
          Solids loading rate, phm 750 to 1,000

Cogeneration

 
     Number 2
     Type 850-kW engine generators