fundamentals of engineering supplied-reference handbook - Ventech!

Bed Expansion
Monosized Multisized
Lo
( 1−
ηo
)
L fb =
L = ( 1−
η )∑
0.
22 fb Lo
o
⎛V
⎞
1−
⎜ B
⎟
⎝ Vt
⎠
0. 22
⎛ VB
⎞
η fb = ⎜ ⎟
⎜ V ⎟
, where
t
⎝
⎠
Lfb = depth of fluidized filter media (m),
VB = backwash velocity (m/s), Q/Aplan,
Vt = terminal setting velocity, and
ηfb = porosity of fluidized bed.
Lo = initial bed depth
ηo = initial bed porosity
Lime-Soda Softening Equations
50 mg/L as CaCO3 equivalent = 1 meq/L
1. Carbon dioxide removal
CO2 + Ca (OH)2 → CaCO3(s) + H2O
x
⎛
⎜
V
1−
⎜
⎝
Vt,
ij
B
i,
j
2. Calcium carbonate hardness removal
Ca (HCO3)2 + Ca (OH)2 → 2CaCO3(s) + 2H2O
3. Calcium non-carbonate hardness removal
CaSO4 + Na2CO3 → CaCO3(s) + 2Na + + SO4 –2
4. Magnesium carbonate hardness removal
Mg(HCO3)2 + 2Ca(OH)2 → 2CaCO3(s) +
Mg(OH)2(s) + 2H2O
5. Magnesium non-carbonate hardness removal
MgSO4 + Ca(OH)2 + Na2CO3 → CaCO3(s) +
Mg(OH)2(s) + 2Na + + SO4 2–
6. Destruction of excess alkalinity
⎞
⎟
⎠
0.
22
2HCO3 – + Ca(OH)2 → CaCO3(s) + CO3 2– + 2H2O
7. Recarbonation
Ca 2+ + 2OH – + CO2 → CaCO3(s) + H2O
164
Molecular
Formulas
CO3 2–
CO2
Ca(OH)2
CaCO3
Ca(HCO3)2
CaSO4
Ca 2+
H +
HCO3 –
Mg(HCO3)2
Mg(OH)2
MgSO4
Mg 2+
Na +
Na2CO3
OH –
SO4 2–
ENVIRONMENTAL ENGINEERING (continued)
Molecular
Weight
60.0
44.0
74.1
100.1
162.1
136.1
40.1
1.0
61.0
146.3
58.3
120.4
24.3
23.0
106.0
17.0
96.1
n
# Equiv per
mole
2
2
2
2
2
2
2
1
1
2
2
2
2
1
2
1
2
Rapid Mix and Flocculator Design
G =
P
=
µ Vol
γH
L
t µ
Equivalent
Weight
30.0
22.0
37.1
50.0
81.1
68.1
20.0
1.0
61.0
73.2
29.2
60.2
12.2
23.0
53.0
17.0
48.0
Gt = 10 4 − 10 5
where
G = mixing intensity = root mean square velocity
gradient,
P = power,
Vol = volume,
µ = bulk viscosity,
γ = specific weight of water,
HL = head loss in mixing zone, and
t = time in mixing zone.
Reel and Paddle
P =
C A ρ V
2
3
D P f p
,where
CD = drag coefficient = 1.8 for flat blade with a
L:W > 20:1,
Ap = area of blade (m 2 ) perpendicular to the direction of
travel through the water,
ρf = density of H2O (kg/m 3 ),
V p = relative velocity of paddle (m/sec), and
V mix = Vp • slip coefficient.
slip coefficient = 0.5 − 0.75.