Encyclopedia of Environmental Science and Engineering, Volume I and II

URBAN RUNOFF 1199

TABLE 25

DAF design parameters

Overflow Rate (gal/ft^2 /min)

Low rate 1.3–4.0

High rate 4.0–10.0

Horizontal Velocity (ft/min) 1.3–3.8

Detention Time (min)

Flotation cell range 10–60

Floating cell average 25

Saturation tank 1–3

Mixing chamber 1

Pressurized Flow (% of total flow)

Split-flow pressurization 20–30

Effluent recycle pressurization 25–45

Air to Pressurized Flow Ratio

(standard ft^3 /100 gal)

1.0

Air to Solids Ratio 0.05–0.35

Pressure in Saturation Tank (lb/in.^2 ) 40–70

Float

Volume (% of total flow) 0.75–1.4

Solids concentration (% dry weight basis) 1–2

lb/in.^2  0.0703 
 kg/m^2.

(EPA-600/8-77-014).

100

100

1 000

1 000

10 000

10 000

100 000

NOTE: 11^2 = 0.0626-m^3

Mgal/s = 0.0438-m^3 /s

DISSOLVED AIR FLOTATION TANK SURFACE AREA, ft^2

CONSTRUCTION COSTS, $ 1 000

ESTIMATED 90 Mgal/d PLANT.

MAINTANENCE VISC [b]

MACINE WIRE FACILITIES

INCLUDE PRETREATMENT [d]

DERIVED FROM

COST CURVE [c]

SAN FRANCISCO, CA [a]

FIGURE 14 DAF construction costs: ENR 
 2,000 (EPA/600/8-77-014).

TABLE 23

Percent removals achieved with screening/DAF (Milwaukee, WI)

Without chemical

flocculant addition

With chemical

flocculant addition

BOD 5 35  8 60  11

COD 41  8 57  11

SS 43  7 71  9

Volatile SS 48  11 71  9

Nitrogen 29  14 24  9

(EPA-600-77-069a).

TABLE 24

Percent removals achieved with screening/DAF (Racine)

Percent Removal

Site I Site II

BOD 5 57.5 65.4

TOC 51.2 64.7

SS 62.2 73.3

Volatile SS 66.8 70.9

Total Phosphorus 49.3 70.0

(EPA-600/2-79-106a).

C021_002_r03.indd 1199C021_002_r03.indd 1199 11/23/2005 9:45:48 AM11/23/2005 9: