Page 768 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

Biological Reactors 723

TABLE 23.2
Some Diffused Air Activated-Sludge Plants in Operation in 1930 with Design Characteristics
Chicago, Houston,
Milwaukee Indianapolis North Side Decatur Manchester North Side Pasadena Toronto
Date of construction 1925 1924 1926 1927 1923 1917 1924 1929
Population served 575,000 360,000 800,000 50,000 18,000 67,000 120,000 50,000
Preliminary treatment
Grit chambers Yes Yes Yes Yes None Yes None Yes
Fine screens Yes Yes None None None None Yes None
Sedimentation (hours) None None 0.5 1.1 0.7 None None 1.6
Aeration tanks
Type Ridge=fur Spiral Spiral Spiral Spiral Ridge=fur Ridge=fur Spiral
Number 24 6 36 6 2 4 30 4
Length (m) 72 72.5 128 36.6 53.9 85.3 20.6 49.7
Width, one channel (m) 6.7 6.1 10.6 4.9 1.9 2.7 3.0 4.0
Depth (m) 4.6 4.6 4.6 4.4 2.1 3.0 4.6 3.2
Passes per tank 2 4 1 1 3 2 1 2
Aeration time (h) 6 4.7 6 2.5 7 2.3 4 4
3
Airflow (ft =gal) 1.5 1 0.8 1 0.9 1.4 1 1
Return sludge fraction 0.25 0.20 0.25 0.1 0.15 0.25 0.33 0.25
Area diffusers=area tank 1:4 1:13 1:9 1:9 1:17 1:7 1:6 1:10
Final sedimentation tanks
Type Dorr Hopper bot. Dorr Dorr Hopper bot. Hopper bot. Hardinge Fidler
Number 11 12 30 2 1 40 5 2
Dimensions (m) 29.9 dia 23.8 12.8 23.5 23.5 23.6 23.6 11.0 11.0 5.8 3.0 15.2 15.2 19.8 19.8
Depth (m) 4.6 4.6 4.9 4.2 6.4 6.7 4.9 4.5
Detention time (h) 1.7 1.6 2 2.6 2 1.5 2 2
2
Surf. loading (gal=ft =d) 850 1380 980 830 1,000 1,330 880 710
Re-aeration tanks
Number None None None None 1 4 5 None
Source: Adapted from Metcalf, L. and Eddy, H.P., Sewerage and Sewage Disposal, McGraw-Hill, New York, 1930.

TABLE 23.3
Performance of Activated-Sludge Plants

Houston, North Side Houston, South Side Indianapolis Milwaukee Pasadena San Marcos Sherman
Year 1923 1923 1927 1927 1928–1929 1920 1920
Period covered 1 year 1 year 1 year 1 year 6 months 10 days 11 days
Suspended solids (mg=L)
Influent 272 166 318 250–300 336 42 264
Effluent 34 9 27 25 15 3 73
Percent removal 87 94 92 90–92 96 92 72
BOD—5 day (mg=L)
Influent 120 236 200–250 207 57 165
Effluent 8 32 6 9 16 33
Percent removal 93 86 97 96 72 80
Ammonia (mg=L)
Influent 19 16 18 17 26
Effluent 7 5 8 3 23
Nitrates in effluent (mg=L) 4 11 0.7 4 4 9 1

Source: Metcalf, L. and Eddy, H.P., Sewerage and Sewage Disposal, McGraw-Hill, New York, 1930.