Predicting the performance of fixed-bed granular - Michigan ...
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PREDICTING THE PERFORMANCE OF<br />
FIXED-BED GRANULAR<br />
ACTIVATED CARBON ADSORBERS<br />
D. W. Hand, J. C. Crittenden, D. R. Hokanson, and J. L. Bulloch<br />
Dept. <strong>of</strong> Civil and Environmental Engineering<br />
<strong>Michigan</strong> Technological University<br />
Houghton, <strong>Michigan</strong> 49931<br />
USA<br />
Presented at First IAWQ Specialized Conference on Adsorption in Water<br />
Environment and Treatment Processes; Shirahama, Wakayama Japan<br />
November 1996<br />
Copyright © 1996-2002. <strong>Michigan</strong> Technological University. All Rights Reserved.<br />
1
OUTLINE<br />
Competitive Interactions<br />
Between Known Components<br />
• Correlation <strong>of</strong> Single Solute Adsorption Equilibria<br />
• Prediction <strong>of</strong> Multicomponent Equilibria <strong>of</strong> Known<br />
Components<br />
• Model Predictions Using <strong>the</strong> Equilibrium Column<br />
Model<br />
• Model Predictions Using <strong>the</strong> Pore Surface Diffusion<br />
Model<br />
2
OUTLINE (continued)<br />
Syn<strong>the</strong>tic Organic Compound (SOC) and Unknown<br />
Background Organic Matter (BOM) Interactions<br />
• Impact <strong>of</strong> BOM on Fixed Bed Adsorption Capacity <strong>of</strong><br />
SOCs<br />
– Influence <strong>of</strong> Exposure Time<br />
– Influence <strong>of</strong> Compound Type<br />
– Influence <strong>of</strong> Water Type<br />
• Impact <strong>of</strong> BOM on Adsorption Rate<br />
• Model Simulations for a Variety <strong>of</strong> Waters<br />
3
Volume Adsor<strong>bed</strong> (ml/g)<br />
1<br />
0.1<br />
0.01<br />
0.001<br />
0.0001<br />
ISOTHERM CORRELATION<br />
Data from 26 chemicals<br />
Correlation<br />
Adsorbent: Calgon F-400 GAC<br />
Data Source: Speth and Miltner (1990)<br />
Wi = Woexp[-β(ε i/Vi) σ ]<br />
Wo = 0.24 ml/g<br />
β = 0.0025 (ml/cal) σ<br />
σ = 1.51<br />
0 50 100 150 200 250<br />
Adsorption Potential / Intrinsic Molar Volume (cal/ml)<br />
4
Volume Adsor<strong>bed</strong> (ml/g)<br />
0.01<br />
0.001<br />
0.0001<br />
MTU DATA FOR SIX COMPONENTS<br />
10<br />
1<br />
0.1<br />
Naphthalene<br />
1,2,4-Trichlorobenzene<br />
Trichloroethylene<br />
Toluene<br />
m-Xylene<br />
Correlation<br />
Adsorbent: Calgon APA GAC<br />
Particle Size: 200 x 400 USTM<br />
Data Source: Bulloch et al. (1995)<br />
Wi = Woexp[-β(ε i/Vi) σ ]<br />
Wo = 1.03 ml/g<br />
β = 0.045 (ml/cal) σ<br />
σ = 1.00<br />
0 20 40 60 80 100 120 140 160<br />
Adsorption Potential / Intrinsic Molar Volume (cal/ml)<br />
5
IDEAL ADSORBED SOLUTION THEORY<br />
C<br />
i<br />
=<br />
g q<br />
i i<br />
N<br />
Â<br />
j=<br />
1<br />
• Wilson Activity Coefficients<br />
q<br />
j<br />
L<br />
M<br />
NM<br />
N<br />
Â<br />
j=<br />
1<br />
nq<br />
nK<br />
i i<br />
ln = 10 . -ln xA-<br />
g i j ij<br />
j=<br />
1<br />
n<br />
Â<br />
j j<br />
( 1-zi<br />
)<br />
i i<br />
g = a<br />
n<br />
Â<br />
k = 1<br />
O<br />
P<br />
QP<br />
L<br />
M<br />
NM<br />
n<br />
Â<br />
j=<br />
1<br />
x A<br />
k ki<br />
xA<br />
j kj<br />
• Empirical Activity Coefficients (less than 1.0)<br />
O<br />
P<br />
QP<br />
6
Solid Phase Concentration<br />
(mMol/g)<br />
10<br />
1<br />
0.1<br />
0.01<br />
IAST CALCULATIONS SHOWING<br />
IMPROVEMENT WITH γ<br />
Adsorbent: Calgon F-400 GAC<br />
Particle Size: 200 x 400 USTM<br />
Temperature: 13 o C<br />
Data Source: Arora (1989)<br />
0.00001 0.0001 0.001 0.01 0.1<br />
Liquid Phase Concentration (mMol/L)<br />
Multicomponent DBCM Data Original DBCM IAST Prediction<br />
DBCM IAST Fit DBCM Single Solute<br />
Multicomponent PCE Data Original PCE IAST Prediction<br />
PCE IAST Fit PCE Single Solute<br />
7
Solid PhaseConcentration<br />
(mMol/g)<br />
0.1<br />
0.01<br />
0.001<br />
IAST CALCULATIONS SHOWING NO<br />
IMPROVEMENT WITH γ<br />
1<br />
Adsorbent: Calgon F-400 GAC<br />
Particle Size: 200 x 400 USTM<br />
Temperature: 13 o C<br />
Data Source: Arora (1989)<br />
0.00001 0.0001 0.001 0.01 0.1<br />
Liquid Phase Concentration (mMol/L)<br />
Multicomponent Chlor<strong>of</strong>orm Data Original Chlor<strong>of</strong>orm IAST Prediction<br />
Chlor<strong>of</strong>orm IAST Fit Chlor<strong>of</strong>orm Single Solute<br />
Multicomponent TCE Data Original TCE IAST Prediction<br />
TCE IAST Fit TCE Single Solute<br />
8
Solid-phase Concentration, (mg/g)<br />
ADSORPTION EQUILIBRIUM ISOTHERM<br />
FOR TRICHLOROETHENE<br />
100<br />
10<br />
1<br />
TRICHLOROETHENE ISOTHERMS<br />
PRELOADING TIME IN WEEKS<br />
CALGON F-100 GAC (12x40 mesh)<br />
v = 10 m/hr<br />
Source: Zimmer et al. (1988)<br />
Single Solute (q=3.27 C 0.458 )<br />
34<br />
70<br />
100<br />
2<br />
7<br />
25<br />
50<br />
1 10 100 1000<br />
Liquid-Phase Concentration, (mg/m 3 )<br />
9
Relative Freundlich Parameter K %<br />
120<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
FREUNDLICH K REDUCTION<br />
FOR VARIOUS WATERS<br />
Houghton GW<br />
(F-400 GAC)<br />
Portage Lake<br />
(F-400 GAC)<br />
Rhine River<br />
(F-100 GAC)<br />
TRICHLOROETHENE<br />
Source: Zimmer et al. (1988)<br />
Hand et al. (1989)<br />
El- Behlil (1990)<br />
Wausau GW<br />
(F-400 GAC)<br />
Karlsruhe GW<br />
(F-100 GAC)<br />
0 10 20 30 40 50 60 70 80<br />
Preloading Time (weeks)<br />
10
C b<br />
Bulk<br />
Solution<br />
r<br />
C s<br />
Linear<br />
Driving<br />
Force<br />
Boundary<br />
Layer<br />
PSDM MECHANISMS<br />
C p,r<br />
Local Equilibrium<br />
Between Fluid Phase<br />
and Adsorbent Phase<br />
R<br />
Dr<br />
q r<br />
r+Dr<br />
Fluid Phase Adsorbent Phase<br />
Mass<br />
Flux<br />
= k fbCb -Csg<br />
Mass<br />
Flux<br />
q<br />
=-Dsra r<br />
-<br />
∂<br />
∂<br />
r<br />
τ p = 1<br />
De∂C t ∂r<br />
r l p<br />
p<br />
pr ,<br />
Pore<br />
Diffusion<br />
Surface<br />
Diffusion<br />
11
MASS TRANSFER COEFFICIENTS<br />
• External Mass Transfer Coefficient (Gnielinski, 1978)<br />
b g �<br />
k f = 1+1.5 1- e fD<br />
2R<br />
2+0.644 Re Sc<br />
1/ 2 1/ 3<br />
12
MASS TRANSFER COEFFICIENTS (continued)<br />
• Intraparticle Surface Diffusion Coefficient<br />
D = SPDFR<br />
s<br />
L<br />
M<br />
N<br />
D C<br />
�e<br />
p<br />
*<br />
0<br />
KC<br />
1/<br />
n<br />
t p 0<br />
r<br />
– Single Components:<br />
• SPDFR between 4 and 8 (mean = 6.58)<br />
– Multiple Components:<br />
• SPDFR = 16.27 EBCT(min) -0.843<br />
a<br />
O<br />
P<br />
Q<br />
13
MASS TRANSFER COEFFICIENTS (continued)<br />
• Intraparticle Pore Diffusion Coefficient<br />
D =<br />
p<br />
e<br />
p<br />
t<br />
D �<br />
– SOCs Alone (maximum pore diffusion flux):<br />
• τp = 1.0<br />
– SOCs in <strong>the</strong> Presence <strong>of</strong> BOM:<br />
• τp = 1.0 when Time < 70 days<br />
• τp = 0.334 + 6.61(10-6 ) * t when Time > 70 days<br />
p<br />
14
ADSORPTION DESIGN SOFTWARE<br />
(AdDesignS TM )<br />
• Gas and Liquid phase<br />
• Visual Basic Front-End with FORTRAN DLLs<br />
• Up To 6 Components (12 PDEs), Solved by<br />
Orthogonal Collocation (Up To 18 Axial and 6 Radial<br />
Points, Up To 126 ODEs for Each Component, 756<br />
ODEs total)<br />
• Structured Heuristics Based on Experience for Model<br />
Parameter Estimation<br />
• Data Base for Iso<strong>the</strong>rms and Adsorbents<br />
• SI and English Units<br />
• 15,000 lines <strong>of</strong> code<br />
15
Liquid Phase Concentration ( µg/L)<br />
2500<br />
2250<br />
2000<br />
1750<br />
1500<br />
1250<br />
1000<br />
750<br />
500<br />
250<br />
0<br />
CHLOROFORM: 6 Component ECM and<br />
PSDM Simulations for Organic Free Water<br />
EBCT =<br />
2.4 min.<br />
EBCT =<br />
9.56 min.<br />
EBCT =<br />
4.9 min.<br />
ECM<br />
EFFLUENT : EBCT = 2.4 min.<br />
EFFLUENT : EBCT = 4.9 min.<br />
EFFLUENT : EBCT = 9.56 min.<br />
INFLUENT : PILOT SCALE<br />
PSDM : EBCT = 2.4 min.<br />
PSDM : EBCT = 4.90 min.<br />
PSDM : EBCT = 9.56 min.<br />
CHLOROFORM F-400 GAC (12 x 40 mesh)<br />
C0,AVG. = 1020.9 mg/L v = 5.12 m/hr T = 13 o C<br />
Data Source: Arora (1989)<br />
0 5 10 15 20 25 30 35 40 45 50<br />
Liters <strong>of</strong> Water Treated Per Gram <strong>of</strong> GAC<br />
16
Liquid Phase Concentration ( µg/L)<br />
5000<br />
4500<br />
4000<br />
3500<br />
3000<br />
2500<br />
2000<br />
1500<br />
1000<br />
500<br />
1,2-DBE RESULT: 6 Component ECM and<br />
PSDM Simulations for Organic Free Water<br />
0<br />
ECM CALCULATION<br />
EFFLUENT : EBCT = 2.4 min.<br />
EFFLUENT : EBCT = 4.9 min.<br />
EFFLUENT : EBCT = 9.56 min.<br />
INFLUENT : PILOT SCALE<br />
PSDM : EBCT = 2.40 min.<br />
PSDM : EBCT = 4.90 min.<br />
PSDM : EBCT = 9.56 min.<br />
EBCT =<br />
2.4 min.<br />
EBCT =<br />
4.9 min.<br />
1,2-DIBROMOETHANE<br />
F-400 GAC (12 x 40 mesh)<br />
C0,AVG. = 1576.8 µg/L<br />
v = 5.12 m/hr<br />
T = 13 o C<br />
Data Source: Arora (1989)<br />
EBCT =<br />
9.56 min.<br />
0 5 10 15 20 25 30 35 40 45 50<br />
Liters <strong>of</strong> Water Treated Per Gram <strong>of</strong> GAC<br />
17
Liquid Phase Concentration ( µg/L)<br />
TCE RESULT: 6 Component ECM and PSDM<br />
Simulations for Organic Free Water<br />
1500<br />
1350<br />
1200<br />
1050<br />
900<br />
750<br />
600<br />
450<br />
300<br />
150<br />
0<br />
EBCT =<br />
9.56 min.<br />
EBCT =<br />
4.9 min.<br />
EBCT =<br />
2.4 min.<br />
ECM CALCULATION<br />
EFFLUENT : EBCT = 2.4 min.<br />
EFFLUENT : EBCT = 4.9 min.<br />
EFFLUENT : EBCT = 9.56 min.<br />
INFLUENT : PILOT SCALE<br />
PSDM : EBCT = 2.40 min.<br />
PSDM : EBCT = 4.90 min.<br />
PSDM : EBCT = 9.56 min.<br />
TRICHLOROETHENE F-400 GAC (12 x 40 mesh)<br />
C0,AVG. = 1062.6 µg/L v = 5.12 m/hr T = 13 o C<br />
Data Source: Arora (1989)<br />
0 20 40 60 80 100 120 140 160<br />
Liters <strong>of</strong> Water Treated Per Gram <strong>of</strong> GAC<br />
18
MODEL VERIFICATION EFFORT<br />
• 11 Case Studies<br />
•<br />
– 9 Pilot Plant Experiments<br />
– 2 Full-Scale Plants<br />
11 Water Sources (USA, Germany, Ne<strong>the</strong>rlands)<br />
– 8 Groundwaters<br />
– 3 Surface Waters<br />
• 4 Adsorbents<br />
• 50 Empty Bed Contact Times<br />
• 15 Syn<strong>the</strong>tic Organic Chemicals<br />
19
Liquid-Phase Concentration ( µg/L)<br />
TCE: PSDM PREDICTION - KARLSRUHE<br />
TAP WATER CORRELATIONS<br />
200<br />
180<br />
160<br />
140<br />
120<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
GROUNDWATER : MANNHEIM, GERMANY<br />
TRICHLOROETHENE (C0 = 90 µg/L)<br />
SURROGATE GROUNDWATER : KARLSRUHE, GERMANY<br />
EBCT : 15.6 min. v = 10 m/hr CALGON F-100 GAC<br />
DATA SOURCE: ZIMMER (1988)<br />
Influent Data<br />
Effluent Data<br />
PDM Model Prediction<br />
0 10 20 30 40 50 60 70 80 90<br />
Liters <strong>of</strong> Water Treated Per Gram <strong>of</strong> GAC<br />
20
Liquid-Phase Concentration ( µg/L)<br />
275<br />
250<br />
225<br />
200<br />
175<br />
150<br />
125<br />
100<br />
75<br />
50<br />
25<br />
0<br />
TCE: PSDM PREDICTION - RHINE<br />
RIVER WATER CORRELATIONS<br />
SURFACE WATER : HUDSON RIVER (WATERFORD, NY)<br />
TRICHLOROETHENE (C0 = 121 µg/L)<br />
SURROGATE SURFACE WATER : RHINE RIVER (GERMANY)<br />
EBCT : 16 min. v = 4 m/hr CALGON F-300 GAC<br />
DATA SOURCE: ALBEN ET AL. (1992)<br />
0 10 20 30 40 50 60 70 80 90 100 110<br />
Liters <strong>of</strong> Water Treated Per Gram <strong>of</strong> GAC<br />
Influent Data<br />
Effluent Data<br />
PDM Model Prediction<br />
21
1,2-DCP: PSDM PREDICTION - KARLSRUHE<br />
TAP WATER CORRELATIONS<br />
Liquid-Phase Concentration ( µg/L)<br />
1.5<br />
1.35<br />
1.2<br />
1.05<br />
0.9<br />
0.75<br />
0.6<br />
0.45<br />
0.3<br />
0.15<br />
0<br />
GROUNDWATER : NETHERLANDS<br />
1,2-DICHLOROPROPANE (C0 = 0.5 µg/L)<br />
SURROGATE GROUNDWATER : KARLSRUHE, GERMANY<br />
EBCT : 14.3 min. v = 7.23 m/hr CALGON F-400 GAC<br />
DATA SOURCE: KRUITHOFF ET AL. (1989)<br />
Influent Data<br />
Effluent Data<br />
PDM Model Prediction<br />
0 10 20 30 40 50 60 70 80 90 100<br />
Liters <strong>of</strong> Water Treated Per Gram <strong>of</strong> GAC<br />
22
BENTAZONE: PSDM PREDICTION - KARLSRUHE<br />
TAP WATER CORRELATIONS<br />
Liquid-Phase Concentration ( µg/L)<br />
2<br />
1.8<br />
1.6<br />
1.4<br />
1.2<br />
1<br />
0.8<br />
0.6<br />
0.4<br />
0.2<br />
0<br />
GROUNDWATER : NETHERLANDS<br />
BENTAZONE (C0 = 0.9 µg/L)<br />
SURROGATE GROUNDWATER : KARLSRUHE, GERMANY<br />
EBCT : 10.2 min. v = 9.0 m/hr CALGON F-400 GAC<br />
DATA SOURCE: KRUITHOFF ET AL. (1992)<br />
0 10 20 30 40 50 60 70 80 90 100<br />
Liters <strong>of</strong> Water Treated Per Gram <strong>of</strong> GAC<br />
Influent Data<br />
Effluent Data<br />
PDM Model Prediction<br />
23
ATRAZINE: PSDM PREDICTION - KARLSRUHE<br />
TAP WATER CORRELATIONS<br />
Liquid-Phase Concentration ( µg/L)<br />
22<br />
20<br />
18<br />
16<br />
14<br />
12<br />
10<br />
8<br />
6<br />
4<br />
2<br />
0<br />
SURFACE WATER : HUDSON RIVER (WATERFORD, NY)<br />
ATRAZINE (C0 = 8.4 µg/L)<br />
SURROGATE SURFACE WATER : RHINE RIVER (GERMANY)<br />
EBCT : 16 min. v = 4 m/hr CALGON F-300 GAC<br />
DATA SOURCE: ALBEN ET AL. (1992)<br />
0 5 10 15 20 25 30 35 40 45 50 55 60<br />
Liters <strong>of</strong> Water Treated Per Gram <strong>of</strong> GAC<br />
Influent Data<br />
Effluent Data<br />
PDM Model Prediction<br />
24
CHLOROFORM: PSDM PREDICTION USING THE<br />
RHINE RIVER WATER FOULING CORRELATION<br />
Liquid Phase Concentration ( µg/L)<br />
2000<br />
1750<br />
1500<br />
1250<br />
1000<br />
750<br />
500<br />
250<br />
0<br />
CHLOROFORM<br />
Portage Lake Water, Houghton, MI USA<br />
F-400 GAC (12 x 40 mesh) Co,AVG. = 1021 µg/L<br />
EBCT = 9.78 min. v = 5.18 m/hr T = 16 o C<br />
Data Source: Arora (1989)<br />
PSDM PREDICTION<br />
INFLUENT DATA<br />
EFFLUENT DATA<br />
0 1 2 3 4 5 6 7 8 9 10 11<br />
Liters <strong>of</strong> Water Treated per Gram <strong>of</strong> GAC<br />
25
Liquid Phase Concentration ( µg/L)<br />
TCE: PSDM PREDICTION USING THE RHINE<br />
RIVER WATER FOULING CORRELATION<br />
2000<br />
1750<br />
1500<br />
1250<br />
1000<br />
750<br />
500<br />
250<br />
0<br />
TRICHLOROETHENE<br />
Portage Lake Water, Houghton, MI USA<br />
F-400 GAC (12 x 40 mesh) Co,AVG. = 881 µg/L<br />
EBCT = 9.78 min. v = 5.18 m/hr T = 16 o C<br />
Data Source: Arora (1989)<br />
PSDM PREDICTION<br />
INFLUENT DATA<br />
EFFLUENT DATA<br />
0 5 10 15 20 25 30<br />
Liters <strong>of</strong> Water Treated per Gram <strong>of</strong> GAC<br />
26
CONCLUSIONS<br />
• AdDesignSTM interfaces several <strong>fixed</strong> <strong>bed</strong> adsorption<br />
models, model parameter estimation methods, and<br />
iso<strong>the</strong>rm and adsorbent data bases.<br />
• AdDesignSTM allows <strong>the</strong> user to make adsorber<br />
•<br />
<strong>performance</strong> predictions with greater ease and<br />
archive <strong>the</strong> results.<br />
The heuristics for determining <strong>the</strong> most appropriate<br />
models and parameters should be considered work in<br />
progress and <strong>the</strong> Adsorption Design S<strong>of</strong>tware can be<br />
greatly improved as more information is ga<strong>the</strong>red on<br />
<strong>the</strong> practical application <strong>of</strong> <strong>the</strong> models.<br />
27
CONCLUSIONS (continued)<br />
• Single component iso<strong>the</strong>rm data can be correlated<br />
using <strong>the</strong> intrinsic molar volume and <strong>the</strong> Polanyi<br />
Potential Theory<br />
• Multicomponent equilibria can be predicted from<br />
single solute iso<strong>the</strong>rms using IAST for similar sized<br />
molecules<br />
• The Equilibrium Column Model can predict <strong>the</strong><br />
longest <strong>bed</strong> life and <strong>the</strong> highest overshoot<br />
concentrations for multicomponent mixtures <strong>of</strong> known<br />
components.<br />
28
CONCLUSIONS (continued)<br />
• The PSDM can predict <strong>the</strong> effluent concentration<br />
history pr<strong>of</strong>iles for multicomponent mixtures <strong>of</strong> known<br />
components.<br />
• The PSDM can simulate <strong>the</strong> effluent concentration<br />
history pr<strong>of</strong>iles for SOCs in <strong>the</strong> presence <strong>of</strong> BOM.<br />
– Reductions in capacity and diffusivities which<br />
were estimated from a ground water and surface<br />
water span <strong>the</strong> range <strong>of</strong> <strong>fixed</strong> <strong>bed</strong> data from 11<br />
different studies.<br />
– Additional comparisons are needed to develop<br />
more general guidelines.<br />
29
FURTHER READING<br />
Crittenden, J.C., N.J. Hutzler, D.G. Geyer, J.L. Oravitz, and G. Friedman, "Transport <strong>of</strong><br />
Organic Compounds with Saturated Groundwater Flow: Model Development and<br />
Parameter Sensitivity," Water Resources Research, 22 (3), 271-284 (1986).<br />
Crittenden, J.C., T.F. Speth, D.W. Hand, P.J. Luft, and B. Lykins, "Evaluating Multicomponent<br />
Competition in Fixed Beds," Journal <strong>of</strong> Environmental Engineering, 113 (6),<br />
1363-1375 (1987a).<br />
Crittenden, J.C., D.W. Hand, H. Arora, and B.W. Lykins Jr., "Design Considerations for<br />
GAC Treatment <strong>of</strong> Organic Chemicals," Jour. <strong>of</strong> AWWA, 79 (1), 74-82 (1987b).<br />
Crittenden, J.C., R.D. Cortright, B. Rick, S.R. Tang, and D. Perram, "Using Granular<br />
Activated Carbon to Remove Volatile Organic Chemicals from Air Stripping Off-Gas,"<br />
Jour. <strong>of</strong> AWWA, 80 (5), 73-84 (1988).<br />
Hand, D. W., J. C. Crittenden, and W. E. Thacker, "Simplified Models for Design <strong>of</strong> Fixed-<br />
Bed Adsorbers," Jour. <strong>of</strong> Env. Eng. Div., Proceedings <strong>of</strong> ASCE, 110 (EE2), 1984.<br />
Hand, D. W., J. C. Crittenden, H. Arora, J. Miller, and B.W.Lykins Jr., "Design <strong>of</strong> Fixed-<br />
Beds to Remove Multi-component Mixtures <strong>of</strong> Volatile and Syn<strong>the</strong>tic Organic<br />
Chemicals," Jour. <strong>of</strong> AWWA, 81(1) 1989.<br />
Hand, D. W., J.C. Crittenden, D.R. Hokanson, and J.L. Bulloch, “<strong>Predicting</strong> <strong>the</strong> <strong>performance</strong><br />
<strong>of</strong> <strong>fixed</strong>-<strong>bed</strong> <strong>granular</strong> activated carbon adsorbers,” Water Science and Technology,<br />
35(7), 235-241 (1997).<br />
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<strong>of</strong> Germany (1988).<br />
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ACKNOWLEDGMENTS<br />
• National Center for Clean Industrial and Treatment<br />
Technologies (CenCITT)<br />
• U.S. Environmental Protection Agency<br />
• National Science Foundation (No. ECE 8603615)<br />
• Environmental Engineering Center (MTU)<br />
• Some laboratory and field data were analyzed and<br />
provided by G. Baldauf, Gerhard Zimmer, and <strong>the</strong><br />
late Pr<strong>of</strong>essor Heinrich Son<strong>the</strong>imer at Engler-Bunte-<br />
Institut, University <strong>of</strong> Karlsruhe<br />
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