fundamentals of engineering supplied-reference handbook - Ventech!
fundamentals of engineering supplied-reference handbook - Ventech!
fundamentals of engineering supplied-reference handbook - Ventech!
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where<br />
R<br />
Cin<br />
= stripping factor H′(QA / QW),<br />
= concentration in the influent water (kmol/m 3 ),<br />
and<br />
Cout = concentration in the effluent water (kmol/m 3 ).<br />
HTU = Height <strong>of</strong> Transfer Units =<br />
M<br />
L<br />
K<br />
,<br />
a<br />
where<br />
L = liquid molar loading rate [kmol/(s•m 2 )],<br />
MW<br />
= molar density <strong>of</strong> water (55.6 kmol/m 3 ) = 3.47<br />
lbmol/ft 3 , and<br />
KLa = overall transfer rate constant (s –1 ).<br />
Clarifier<br />
Overflow rate = Hydraulic loading rate = V o = Q/Asurface<br />
Weir overflow rate = WOR = Q/Weir Length<br />
Horizontal velocity = Approach velocity = V h<br />
= Q/Across-section = Q/Ax<br />
Hydraulic residence time = Vol/Q = θ<br />
where<br />
Q = flow rate,<br />
Ax = cross-sectional area,<br />
A = surface area, plan view, and<br />
Vol = tank volume.<br />
Design Criteria for Sedimentation Basins<br />
W<br />
L<br />
162<br />
ENVIRONMENTAL ENGINEERING (continued)<br />
Typical Primary Clarifier Efficiency Percent Removal<br />
Suspended<br />
Solids<br />
Overflow rates<br />
1,200 1,000 800 600<br />
(gpd/ft 2 ) (gpd/ft 2 ) (gpd/ft 2 ) (gpd/ft 2 )<br />
48.9 40.7 32.6 24.4<br />
(m/d) (m/d) (m/d) (m/d)<br />
54% 58% 64% 68%<br />
BOD5 30% 32% 34% 36%<br />
Design Data for Clarifiers for Activated-Sludge Systems<br />
Overflow rate,<br />
m 3 /m 2 ⋅d<br />
Loading<br />
kg/m 2 ⋅h<br />
Type <strong>of</strong> Treatment Average Peak Average Peak<br />
Depth<br />
(m)<br />
Settling following<br />
air-activated sludge<br />
(excluding extended<br />
aeration) 16−32 40−48 3.0−6.0 9.0 3.5−5<br />
Settling following<br />
extended aeration 8−16 24−32 1.0−5.0 7.0 3.5−5<br />
Adapted from Metcalf & Eddy, Inc. [5−36]<br />
Type <strong>of</strong> Basin Overflow Rate (gpd/ft 2 ) Hydraulic Residence Time (hr)<br />
Water Treatment<br />
Presedimentation 300−500 3−4<br />
Clarification following coagulation and flocculation<br />
1. Alum coagulation 350−550 4−8<br />
2. Ferric coagulation 550−700 4−8<br />
3. Upflow clarifiers<br />
a. Ground water 1,500−2,200 1<br />
b. Surface water 1,000−1,500 4<br />
Clarification following lime-soda s<strong>of</strong>tening<br />
1. Conventional 550−1,000 2–4<br />
2. Upflow clarifiers<br />
a. Ground water 1,000−2,500 1<br />
b. Surface water 1,000−1,800 4<br />
Wastewater Treatment<br />
Primary clarifiers 600−1,200 2<br />
Fixed film reactors<br />
1. Intermediate and final clarifiers 400−800 2<br />
Activated sludge 800−1,200 2<br />
Chemical precipitation 800−1,200 2
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