Water and Wastewater Engineering
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28-34 WATER AND WASTEWATER ENGINEERING
3. Given a process flow sheet and raw wastewater characteristics, identify the
characteristics or upstream processes that point to the selection of each of the processes.
W ith the aid of this text, you should be able to do the following:
4 . Given a process flow sheet and raw wastewater characteristics, identify alternative pro-
cesses that may have or should have been considered.
5. Given raw wastewater characteristics and design criteria, perform a screening analysis to
select an initial set of processes for further evaluation.
6. Given a selec ted list of processes, organize them into a treatment train and draw and
label a process flow diagram.
28-6 PROBLEMS
28-1. Assume that The Colony (Case Study 28-1) decided to build a new clean water plant
at a new location where space is not limited but that effluent standards are more
stringent. The standards for CBOD, TSS, and NH
4
+
-N remained the same, but a total
phosphorus limit of 1.0 mg/L is added to the permit requirements. Select a treatment
train that can meet the new discharge standards. Class A biosolids are to be produced.
28-2. Assume that the PARCC Side Clean Water Plant shown in Figure 28-5 is concerned
with overloading the proposed 1 mm fine
screens. What alternative(s) in the process
flowsheet would you propose?
28-3. A proposed upscale residential development, Sunrise Estates, has been proposed.
The location is in a y ear-round warm weather climate. A new, on-site, clean water
plant must be built for the d evelopment. The assumed influent parameters and
state
standard for groundwater discharge are shown below. Select a treatment process
train that can meet the discharge standards. Class B biosolids are to be produced,
and 45 days of storage are to be provided before agricultural disposition.
Sunrise Estates Clean Water Plant data
Parameter Influent flow or concentration Effluent standard
Average day influent 2,000 m
3
/d
Peak day peaking factor 2.0
Peak hour peaking factor 2.5
CBOD 225 mg/L < 5 mg/L
TSS 240 mg/L < 5 mg/L
Total N 40 mg/L < 4 mg/L
Total P 7 mg/L < 2 mg/L
Fecal coliforms N/A nondetect
28-4. Recalculate the elevation top of the top of the chlorine contact wall in Figure P-28-4
if a vortex grit chamber is used in place of the aerated grit chamber.
CLEAN WATER PLANT PROCESS SELECTION AND INTEGRATION 28-35
26
24
Maximum w.s
El. 24.76
Weir
El. 23.95
Aerated
grit chamber
V-notch weir
El. 23.30
Top of wall
El. 24.64
Maximum w.s.
El. 23.35
Top of wall
El. 23.93
Top of wall
El. 23.17
Maximum w.s.
El. 22.59
Weir crest
El. 22.50
Chlorine
contact tanks
Top of wall
El. 22.71
Maximum w.s.
El. 22.13
V-notch weir
El. 22.07
Weir
El. 21.
56
Maximum w.s.
El.
21.64
El. 23.17
Top of wall
El. 23.32
42-year frequency w.s.
El. 23.01 (for primary
treatment only)
15-year frequency
w.s. El. 21.12 (for
full secondary
treatment)
Hydraulic grade line for a flow rate
of 45,000 m
3
/d
22
Elevation, m
20
18
16
Primary tanks Aeration tanks
Final setting tanks
FIGURE P-28-4
H ydraulic profiles for clean water plant. ( Note: WS water surface.)
28-5. Develop the hydraulic profile for the average flow for the portion of the clean water
plant shown in Figure P-28-5 . Use the following assumptions (Metcalf & Eddy,
1991):
Average fl ow rate 7,500 m
3
/ d plus 100% recycle
Two primary clarifi ers each with a diameter of 13.75 m
T w o secondary clarifi ers each with a diameter of 15 m
90 v-notch weirs with notches at 0.3 m intervals are used around the periphery
of the clarifi ers
520
El.
519.17
El. 518.00
El. 513.90
El.
516.00
El.
518.26
15 m
2–40 cm lines
38 m
Secondary
clarification
tanks
Aeration
tanks
Primary
clarification
tanks
2 tanks
13.75 m
1–50 cm line
46.50 m
519
518
517
Elevation, m
516
515
514
El.
519.10
El.
519.00
El.
519.50
FIGURE P-28-5
H ydraulic profile for clean water plant.
28-36 WATER AND WASTEWATER ENGINEERING
RAS is returned directly to the aeration tank
A Francis-type weir with two end contractions is used for the aeration tank
overfl ow weir
Ignore channel and pipe losses
28-6. Develop the hydraulic profile for the peak flow for the portion of the clean water
plant shown in Figure P-28-5 . Use a peak flow rate of 15,000 m
3
/ d and, with the
exception of the flow rate, the same assumptions as those in Problem 28-5.
28-7 REFERENCES
Coté, P., D. Brink, and A. Adnan (2007) “Prerequisite Pretreatment,” Water Environment and
Technology, vol. 19, no. 3, March, pp. 40–45.
Davis, M. L. and D. A. Cornwell (2008) Introduction to Environmental Engineering, 4th ed.,
McGraw-Hill, New York.
G ujer, W., M. Henze, T. Mino, and M. Loosdrecht (1999) “Activated Sludge Model No. 3,” Water
Science and Technology, vol. 39, no. 1, pp. 183–193.
Jackson, D. R., L. E. Ripley, T. Maurina, and S. Hubbell (2007) “Up to the Challenge,” Water
Environment and Technology, vol. 19, November, pp. 51–55.
Metcalf & E
ddy (1991) Wastewater Engineering: Treatment, Disposal and Reuse, 3rd ed., McGraw-Hill,
New York, pp. 166–191.
Metcalf & Eddy (2003) Wastewater Engineering: Treatment and Reuse, 4th ed., McGraw-Hill, Boston,
Massachusetts, pp. 429–430, 452–453, 563–886.
Shaw, A., H. M. Phillips, B. Sabherrwal, and C. DeBarbadillo (2007) “Succeding at Simulation, Water
Environment and Technology, vol. 19 April, pp. 54–58.
WEF (1998) Design of Municipal Wastewater Treatment Plants, 4th ed., Water Environment Federation
Manual of Practice 8, Alexandria, Virginia, pp. 3-1–3-52, 15-7 –15-8, 16-5–16-7, 20-113, 22-8–22-9.
WEF (2006a) Clarifier Design, 2nd ed., Water Environment Federation Manual of Practice No. FD-8,
Alexandria, Virginia.
WEF (2006b) Biological Nutrient Removal (BNR) Operation in Wastewater Treatment Plants, Water
Environment Federation, Water Environment Federation Manual of Practice 30, Alexandria,
Virginia, pp. 25, 105–226.
WEF (2006c) Membrane Systems for Wastewater Treatment, Water Environment Federation, Alexandria,
Virginia, pp. 61–62.
WPCF (1989) “Technology and Design Deficiencies at Publicly Owned Treatment Works,” Water
Environment and Technology, vol. 1, p. 515.
A-11
APPENDIX
A
PROPERTIES OF AIR, WATER,
AND SELECTED CHEMICALS
TABLE A-1
Physical properties of water at 1 atm
Temperature
(°C)
Density,
(kg/m
3
)
Specific weight,
(kN/m
3
)
Dynamic viscosity,
(mPa s)*
Kinematic viscosity,
(m
2
/s)*
0 999.842 9.805 1.787 1.787
3.98 1,000.000 9.807 1.567 1.567
5 999.967 9.807 1.519 1.519
10 999.703 9.804 1.307 1.307
12 999.500 9.802 1.235 1.236
15 999.103 9.798 1.139 1.140
17 998.778 9.795 1.081 1.082
18 998.599 9.793 1.053 1.054
19 998.408 9.791 1.027 1.029
20 998.207 9.789 1.002 1.004
21 997.996 9.787 0.998 1.000
22 997.774 9.785 0.955 0.957
23 997.542 9.783 0.932 0.934
24 997.300 9.781 0.911 0.913
25 997.048 9.778 0.890 0.893
26 996.787 9.775 0.870 0.873
27 996.516 9.773 0.851 0.854
28 996.236 9.770 0.833 0.836
29 995.948 9.767 0.815 0.818
30995.650 9.764 0.798 0.801
35 994.035 9.749 0.719 0.723
40 992.219 9.731 0.653 0.658
45 990.216 9.711 0.596 0.602
50 988.039 9.690 0.547 0.554
60 983.202 9.642 0.466 0.474
70 977.773 9.589 0.404 0.413
80 971.801 9.5300.355 0.365
90 965.323 9.467 0.315 0.326
100 958.366 9.399 0.282 0.294
*Pa s (mPa s) 10
3
*m
2
/s (m
2
/s) 10
6
A-2 WATER AND WASTEWATER ENGINEERING
TABLE A-2
Saturation values of dissolved oxygen in freshwater exposed to a saturated
atmosphere containing 20.9% oxygen under a pressure of 101.325 kPa
a
Temperature
(C)
Dissolved oxygen
(mg/L)
Saturated vapor
pressure (kPa)
0 14.62 0.6108
1 14.23 0.6566
213.84 0.7055
3 13.48 0.7575
413.13 0.8129
5 12.80 0.8719
6 12.48 0.9347
7 12.17 1.0013
8 11.87 1.0722
9 11.59 1.1474
10 11.33 1.2272
11 11.08 1.3119
12 10.83 1.4017
13 10.60 1.4969
14 10.371.5977
15 10.15 1.7044
16 9.95 1.8173
17 9.74 1.9367
18 9.54 2.0630
19 9.35 2.1964
20 9.17 2.33
73
21 8.99 2.4861
22 8.83 2.6430
23 8.68 2.8086
24 8.53 2.9831
25 8.38 3.1671
26 8.22 3.3608
27 8.07 3.5649
28 7.92 3.7796
29 7.77 4.0055
30 7.63 4.2430
317.51 4.4927
32 7.42 4.7551
33 7.28 5.0307
34 7.17 5.3200
35 7.07 5.6236
36 6.96 5.9422
37 6.86 6.2762
38 6.75 6.6264
a
For other barometric pressures, the solubilities vary approximately in proportion to the ratios
of these pressures to the standard pressures.
(Source: Calculated by G. C. Whipple and M. C. Whipple from measurements of C. J. J. Fox,
Journal of the American Chemical Society, vol. 33, p. 362,
1911.)
PROPERTIES OF AIR, WATER, AND SELECTED CHEMICALS A-3
Molecular weight
M
18.02
Gas constant
R
461.4 J/kg K
Specific heat
c
4,181 J/kg K
Prandtl number
Pr
6.395
Thermal conductivity
k
0.604 W/m K
TABLE A-3
Properties of saturated water at 298 K
Standard atmospheric pressure
P
atm
101.325 kPa
Standard gravitational acceleration
g
9.8067 m/s
2
Universal gas constant
R
u
8,314.3 J/kg mol K
Electrical permittivity constant
0
8.85 10
12
C/V m
Electron charge
q
e
1.60 10
19
C
Boltzmann’s constant
k
1.38 10
23
J/K
TABLE A-4
Frequently used constants
SubstanceEquilibrium equation
pK
a
Significance
Acetic acid CH
3
COOH H
CH
3
COO
4.75 Anaerobic digestion
Carbonic acid
H
2
CO
3
(CO
2
H
2
O) H
HCO
3
6.35 Corrosion, coagulation
H
10.33 softening, pH control
Hydrogen sulfideH
2
S H
HS
7.2 Aeration, odor control
HS
H
S
2
11.89 corrosion
Hypochlorous acid HOCl H
OCl
7.54Disinfection
Phosphoric acid H
3
PO
4
H
2.12 Phosphate removal,
H
2
PO
4
H
7.20 plant nutrient,
H
12.32 analytical
TABLE A-5
Selected weak acid dissociation constants at 25C
Davis and Cornwell, 2008
PO
4
3
H
PO
24
HPO
4
2
HPO
4
2
HCO
3
CO
3
2
A-4 WATER AND WASTEWATER ENGINEERING
TABLE A-6
Typical solubility product constants
(Sources: Linde, 2000; Sawyer, McCarty, and Parkin, 2003; Weast, 1983.)
Equilibrium equation
K
sp
at 25C
AgCl Ag
Cl
1.76 10
10
Al(OH)
3
Al
3
3OH
1.26 10
33
AlPO
4
Al
3
PO
4
3
9.84 10
21
BaSO
4
Ba
2
1.05 10
10
Cd(OH)
2
Cd
2
2OH
5.33 10
15
CdS Cd
2
S
2
1.40 10
29
CdCO
3
Ca
2
6.20 10
12
CaCO
3
Ca
2
CO
3
2
4.95 10
9
CaF
2
Ca
2
2F
3.45 10
11
Ca(OH)
2
Ca
2
2OH
7.88 10
6
Ca
3
(PO
4
)
2
3Ca
2
2.02 10
33
CaSO
4
Ca
2
SO
2
4
4.93 10
5
Cr(OH)
3
Cr
3
3OH
6.0 10
31
Cu(OH)
2
Cu
2
2OH
2.0 10
19
CuS Cu
2
S
2
1.0 10
36
Fe(OH)
3
Fe
3
3OH
2.67 10
39
FePO
4
Fe
3
PO
4
3
1.3 10
22
FeCO
3
Fe
2
CO
2
3
3.13 10
11
Fe(OH) Fe
2
2OH
4.79 10
17
FeS Fe
2
S
2
1.57 10
19
PbCO
3
Pb
2
CO
2
3
1.48 10
13
Pb(OH)
2
Pb
2
2OH
1.40 10
20
PbS Pb
2
S
2
8.81 10
29
Mg(OH)
2
Mg
2
2OH
5.66 10
12
MgCO
3
Mg
2
CO
3
2
1.15 10
5
MnCO
3
Mn
2
CO
3
2
2.23 10
11
Mn(OH)
2
Mn
2
2OH
2.04 10
13
NiCO
3
Ni
2
CO
3
2
1.45 10
7
Ni(OH)
2
Ni
2
2OH
5.54 10
16
NiS Ni
2
S
2
1.08 10
21
SrCO
3
Sr
2
CO
3
2
5.60 10
10
Zn(OH)
2
Zn
2
2OH
7.68 10
17
ZnS Zn
2
S
2
2.91 10
25
SO
4
2
2
4
PO
3
CO
3
2
PROPERTIES OF AIR, WATER, AND SELECTED CHEMICALS A-5
Molecular weight
M
28.97
Gas constant
R
287 J/kg K
Specific heat at constant pressure
c
p
1,005 J/kg K
Specific heat at constant volume
c
v
718 J/kg K
Density
1.185 kg/m
3
Dynamic viscosity
1.8515 10
5
Pa s
Kinematic viscosity
1.5624 10
5
m
2
/s
Thermal conductivity
k
0.0257 W/m K
Ratio of specific heats, c
p
/c
v
k
1.3997
Prandtl number
Pr
0.720
TABLE A-7
Properties of air at standard conditions
a
a
Measured at 101.325 kPa pressure and 298 K temperature.
TABLE A-8
Henry’s law constants at 20C
H*
(atm)
H
u
†
(dimensionless)
H
D
†
(atm L/mg)
H
m
†
(atm m
3
/mol)
Oxygen 4.3 10
4
3.21 10 2.42 10
2
7.73 10
1
Methane 3.8 10
4
2.84 10 9.71 10
2
6.38 10
1
Carbon dioxide1.51 10
2
1.13 10
1
6.17 10
5
2.72 10
3
Hydrogen sulfide 5.15 10
2
3.84 10
1
2.72 10
4
9.26 10
3
Vinyl chloride 3.55 10
5
2.65 10
2
1.02 10
1
6.38
Carbon tetrachloride 1.29 10
3
9.63 10
1
1.51 10
4
2.32 10
2
Trichloroethylene 5.5 10
2
4.1 10
1
7.46 10
5
9.89 10
3
Benzene 2.4 10
2
1.8 10
1
5.52 10
5
4.31 10
3
Chloroform 1.7 10
2
1.27 10
1
2.55 10
5
3.06 10
3
Bromoform 3.5 10 2.61 10
2
2.40 10
6
6.29 10
4
Ozone 5.0 10
3
3.71 1.87 10
3
8.99 10
2
*H values from Montgomery, 1985.
†H
u
, H
D
, and H
m
calculated via Eqs. A-1 to A-4
The dimensionless or unitless Henry’s law constant is:
p H
u
c (A-1)
Where p concentration units, e.g., kg/m
3
, mol/L, mg/L
H
u
unitless
c same concentration units used for p
A-6 WATER AND WASTEWATER ENGINEERING
At 1 atm pressure and 0C, 22.412 L of air is 1 mol of air. At other temperatures, 1 mol of air is 0.082T L
[where T temperature in kelvin (K)] of air. The following conversion between H and H
u
can be made:
HH
u
c
atm (mol gas/mol air)
mol gas/mol water
dda ba b
mol air
0.082 L air
L water
molT 55 6.
H
T
HH
u
4.56
or 7.49 10 at 20 C
4
(A-2)
Another method for reporting Henry’s constant is to use mixed units for p and c.
p
H
P
m
T
c
(A-3)
Where p mol gas/mol air (partial pressure)
c mol gas/m
3
water
H
m
atm m
3
water/mol gas
cdaH
atm (mol gas/mol air)
mol
g
as /mol water
mmwater
55,600 mol
3
b
H
55,600
Alternatively, milligram per liter units for c may be used:
p
H
P
D
T
c
(A-4)
Where p mol gas/mol air (partial pressure)
c mg/L
H
D
(atm)(L)/mg
H
HH
D
m
MW 55
,
600 MW
MW
molecular weight of gas of interest
The Henry’s law coefficient varies both with the temperature and the concentration of other dissolved
substances.
PROPERTIES OF AIR, WATER, AND SELECTED CHEMICALS A-7
Name Formula M.W.
Density,
g/mL
Vapor
pressure,
mm Hg
Henry’s law
constant
kPa m
3
/mol
Acetone CH
3
COCH
3
58.08 0.79 184 0.01
Benzene C
6
H
6
78.11 0.879 95 0.6
Bromodichloromethane CHBrCl
2
163.8 1.971 0.2
Bromoform CHBr
3
252.75 2.8899 5 0.06
Bromomethane CH
3
Br 94.94 1.6755 1,300 0.5
Carbon tetrachloride CCl
4
153.82 1.594 90 3
Chlorobenzene C
6
H
5
Cl 112.56 1.107 12 0.4
Chlorodibromomethane CHBr
2
Cl 208.29 2.451 50 0.09
Chloroethane C
2
H
5
Cl 64.52 0.8978 700 0.2
Chloroethylene C
2
H
3
Cl 62.5 0.912 2,5504
Chloroform CHCl
3
119.39 1.4892 190 0.4
Chloromethane CH
3
Cl 50.49 0.9159 3,750 1.0
1,2-Dibromoethane C
2
H
2
Br
2
187.87 2.18 10 0.06
1,2-Dichlorobenzene 1,2-Cl
2
-C
6
H
4
147.01 1.3048 1.5 0.2
1,3-Dichlorobenzene 1,3-Cl
2
-C
6
H
4
147.01 1.2884 2 0.4
1,4-Dichlorobenzene 1,4-Cl
2
-C
6
H
4
147.01 1.2475 0.7 0.2
1,1-Dichloroethylene
CH
2
PCCl
2
96.94 1.218 500 15
1,2-Dichloroethane ClCH
2
CH
2
Cl 98.96 1.2351 60 0.1
1,1-Dichloroethane CH
3
CHCl
2
98.96 1.1757 180 0.6
Trans-1,2-Dichloroethylene
CHClPCHCl
96.94 1.2565 300 0.6
Dichloromethane CH
2
Cl
2
84.93 1.327 3500.3
1,2-Dichloropropane CH
3
CHClCH
2
Cl 112.99 1.1560 50 0.4
Cis-1,3-Dichloropropylene
ClCH
2
CHPCHCl
110.97 1.217 40 0.2
Ethyl benzene C
6
H
5
CH
2
CH
3
106.17 0.8670 9 0.8
Formaldehyde HCHO 30.05 0.815
Hexachlorobenzene C
6
Cl
6
284.79 1.5691
Pentachlorophenol Cl
5
C
6
OH 266.34 1.978
Phenol C
6
H
5
OH 94.11 1.0576
1,1,2,2-Tetrachloroethane CHCl
2
CHCl
2
167.85 1.5953 5 0.05
Tetrachloroethylene
Cl
2
CPCCl
2
165.83 1.6227 15 3
Toluene C
6
H
5
CH
3
92.14 0.8669 28 0.7
1,1,1-Trichloroethane CH
3
CCl
3
133.41 1.3390 100 3.0
1,1,2-Trichloroethane CH
2
ClCHCl
2
133.41 1.4397 25 0.1
Trichloroethylene
ClHCPCCl
2
131.29 1.476 50 0.9
Vinyl chloride
H
2
CPCHCl
62.50 0.9106 2,200 50
o-Xylene
1,2-(CH
3
)
2
C
6
H
4
106.17 0.8802 6 0.5
m-Xylene
1,3-(CH
3
)
2
C
6
H
4
106.17 0.8642 8 0.7
p-Xylene
1,4-(CH
3
)
2
C
6
H
4
106.17 0.8611 8 0.7
TABLE A-9
Properties of selected organic compounds
Note: Ethene ethylene; ethyl chloride chloroethane; ethylene chloride 1,2-dichloroethane; ethylidene chloride
1,1-dichloroethane; methyl benzene toluene; methyl chloride chloromethane; methyl chloroform 1,1,1-trichloroethane;
methylene chloride dichloromethane; tetrachloromethane c
arbon tetrachloride; tribromomethane bromoform.