Sludge Processing Facilities

Sludge Processing Facilities 1995 2015
Primary Sludge (lb/d)
Average 28,400 38,300
Maximum-Month 44,000 58,200
Maximum 3-Day 62,100 83,500
Secondary Sludge (lb/d)
Average 15,700 21,800
Maximum-Month 28,700 38,500
Maximum 3-Day 36,700 48,600
Skimmings (lb/d) 1,600 1,800
Total Sludge & Skimmings (lb/d)
Average 45,700 61,900
Maximum-Month 74,300 98,500
Maximum 3-Day 100,400 133,900
Gravity Thickeners (Primary Sludge)
No. of Units 3 4
Diameter, ft 40 4.0
Sidewater depth, ft 10 10
Percent Feed Solids 0.2-1.0 0.2-1.0
Average 7.5 7.4
Maximum-Month 11.7 11.6
Maximum 3-Day 16.5 16.6
Hydraulic Loading Rate, gpd/sf 600 600
Thickened Solids % 5.0-6.0 5.0-6.0
Solids Capture % 90 90
Gravity Belt Thickeners(Secondary Sludge)
Number (including one standby) 4 4
Size of Units, meters 2 2
Percent Feed Solids 0.5 0.5
Solids Loading Rate, gpm/m 438 438
Hydraulic Loading Rate, gpm/m 175 175
No. of Units Operating 3 3
Operating Schedule:
Days/Week 7 7
Hours/Day
Average 6.0 8.2
Maximum-Month 11.0 14.7
Maximum 3-Day 14.0 18.5
Thickened Solids, % 5.0 5.0
Solids Capture, % 95 95
Polymer Usage, lb/dry ton 5.0-7.0 5.0-7.0
Sludge Blending/Storage Tanks
Number 6 6
Volume per tank (cu ft) 12,700 12,700
Available Storage (days)
Average 5.7 4.4
Maximum 3.5 2.6
Mixing Blowers
Type Rotary Positive Displacement
Number of Blowers 5 5
Capacity (cfm) 480 480
Horsepower 30 30
Centrifuges
No. of Units 4 4
Percent Feed Solids 5 5
Solids Loading Rate lb/hr/unit 3,000 3,000
Hydraulic Loading Rate, gpm per unit 120 120
Operating Schedule
Day/Week 5 5
Hours/Day
Average 6.5 9
Maximum-Month 11 14
Maximum 3-Day 14 19
Cake Solids, % 28-30 28-30
Solids Capture, % 95 95
Polymer Usage, lb/dry ton 8.5 8-15
Sludge Hauling
Dewatered Sludge Conc., % 28-30 28-30
Sludge Volume (5 days/wk)
Average (cu yd/d) 116 162
Maximum-Month (cu yd/d) 242 322
Hours of Operation (5 days/wk)
Average (hrs/day) 7 7
Maximum-Month (hrs/day) 7 7
Truck Round Trips per day, 5 days/wk (20 cy truck)
Average 6 8
Maximum-Month 12 16
  1. Includes solids processing sidestreams
  2. High groundwater season
  3. For Maximum-Month Loadings during high groundwater season

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