Acknowledgments
Graduate Students:
AECOM:
Evoqua:
Bryce Harada
Yanling Li,
Colin Nguyen,
Krishna Lamichhane,
Gloria Cheong,
Leonardo Postacchini
Lambert Yamashita
Seungdon Joo
Fan Feng
Marta Riendeau
Adam Redding
Problem Statement
Hawaii’s groundwater is contaminated with 1,2,3 –
Trichloropropane (TCP) and DBCP and EDB and a
method of removal is necessary.
 1,2,3 – Trichloropropane (TCP) - Contaminant
 Soil fumigant on pineapple fields
 Potential human carcinogen
 Introduced to Hawaii in 1948 / Banned in 1977
 Contamination still persist today
 Granular Activated Carbon (GAC) - Treatment medium
 Effective, efficient method for TCP removal
 Currently used (~120 contactors, 1 MGD ea)
 Technological advancement; New GAC prototypes designed
3
Objective
The objective was to determine:
 Most effective GAC for TCP removal from Oahu’s groundwater
 Analytical method able to detect TCP concentration = 1 ppt
 GACs meet new potential Hawaii MCL = 5 ppt
Selected GACs
GAC ID
GAC Name
Calgon coconut shell carbon OLC 12x40
Jacobi direct-activated coal based carbon 8x30 (currently used by BWS)
Siemens enhanced coconut shell carbon CX12x30
Siemens coconut shell carbon C12x30
Calgon carbon coal based carbon F400 12x40
Jacobi coconut shell carbon 12x40
Selected Water Well Sites
1. Kunia Wells I GAC Water Treatment Facility
2. Mililani Wells I GAC Water Treatment Facility
3. Waipahu Wells III GAC Water Treatment Facility
Mililani I
Waipahu III
Kunia I
1,2,3 - Trichloropropane
Regulations
 No Federal Maximum Contaminant Level (MCL)
 State of Hawaii MCL = 600 ppt
 California Notification Level = 5 ppt
 Considering to lower Hawaii’s MCL to 5 ppt
Granular Activated Carbon (GAC)
What is GAC?
 Made of:




Coal
Coconut Shells
Lignite
Wood
Full – Scale GAC
Small – Scale GAC
 High surface area to pore volume ratio
 Ideal for contaminant adsorption
Granular Activated Carbon (GAC)
C/Co
Time in Operation or Bed – Volumes
Rapid Small – Scale Column Test
(RSSCT)
 Developed by J.C. Crittenden
 Predicts full – sized GAC adsorption from small,
bench – scale GAC units
 Main advantages of RSSCT
1. Less time compared to pilot studies
2. No isotherm and kinetic studies as in mathematical
prediction models
3. Low amount of water volume
4. Cost efficient
Rapid Small – Scale Column Test
(RSSCT)
Scaling Equations (constant diffusivity assumption)
𝐸𝐵𝐶𝑇𝑠𝑐
𝑅𝑠𝑐
=
𝐸𝐵𝐶𝑇𝑙𝑐
𝑅𝑙𝑐
2
𝑡𝑠𝑐
=
𝑡𝑙𝑐
𝑉𝑠𝑐 𝑅𝑙𝑐
=
𝑉𝑙𝑐 𝑅𝑠𝑐
EBCT = empty bed contact time (min), R = avg particle diameter (mm),
t = test time (hr), V = hydraulic loading rate (mm/min)
Methods/Procedures
Steps
 Water collection from well site
 Transport water to lab for RSSCT
 RSSCT water sample collection every 8 hours (~ 10,000 BV)
 TCP extraction
 TCP analysis
GAC Properties
GAC ID
A/B, F, G
Mesh Size
US Sieve No.
12x40
(1.68 mm x
0.42 mm)
GAC Avg. Particle
Size
1.00 mm
Full - Scale
D, E
C
A/B, F, G
Small - Scale
D, E
12x30
(1.68 mm x
0.595 mm)
8x30
(2.38 mm x
0.595 mm)
170x200
(0.088 mm x
0.075 mm)
170x200
(0.088 mm x
0.075 mm)
170x200
(0.088 mm x
0.075 mm)
1.14 mm
1.49 mm
0.082 mm
0.082 mm
0.082 mm
C
Flow Rate v5
3785 m3/d
5.10 mL/min
6.63 mL/min
11.32 mL/min
Flow Rate v3
3785 m3/d
4.35 mL/min
5.66 mL/min
9.67 mL/min
Column Diameter
3.66 m
4.76 mm
Column Depth
2.59 m
2.00 cm
Column Volume
27.2 m3
0.355 mL
EBCT
Fill Weight
10.355 min
30000 lbs
0.070 min
0.054 min
0.178 g
0.031 min
RSSCT Test Apparatus
GAC Column
Water Sampling
Water Pump
RSSCT Components
GAC Column
Water Pumping Meter
TCP Contaminated Water
RSSCT Components
Water sample effluent – 300 mL BOD bottle
2 mL vials
TCP Extraction Set – Up
Analytical (modified EPA Method 504.1)
 Extraction:
 200ml sample, separatory funnel, 35 g NaCl, 2.0 ml Hexane
 Shake 2 min, let separate, drain water
 Drain hexane layer through sodium sulfate pipette into 2-ml
autosampler vial
 GC:





Restek Rtx-CL Pesticides, 30m, 0.32mmID, 0.25mm
Injection, splitless, 200C, 18psi, He carrier gas, 5ml/min
Electron capture detector (ECD), 300C, N2 makeup
40C/2min – 145C@30c/min – 300C@70C/min, hold 6.3 min (14)
RT = 4.2 min, DL = 1 ppt
Results
 Breakthrough curves
 1%, 5%, and 10% breakthrough points
 Bedvolumes treated
 TCP adsorbed per GAC mass
Influent TCP Concentrations and
Breakthrough Limits
Run #
Water Source
Influent
Concentration (ppb)
1% Breakthrough
(ppb)
5% Breakthrough
(ppb)
10% Breakthrough
(ppb)
2
3
4
5
6
7
8
9
10
11
Kunia I
Kunia I
Waipahu III
Waipahu III
Mililani I
Mililani I
Kunia I
Waipahu III
Waipahu III
Waipahu III
0.818
0.794
0.554
0.554
2.146
2.298
0.803
0.634
0.634
0.506
0.0082
0.0079
0.0064
0.0055
0.0215
0.0230
0.0080
0.0063
0.0063
0.0051
0.0409
0.0397
0.0321
0.0277
0.1073
0.1149
0.0401
0.0317
0.0317
0.0253
0.0818
0.0794
0.0641
0.0554
0.2146
0.2298
0.0803
0.0634
0.0634
0.0506
Water Source
Average Influent
Concentration (ppb)
Kunia I
Mililani I
Waipahu III
~ 0.8
~ 2.2
~ 0.6
GAC A/B Results
TCP Breakthrough Curve - GAC A/B
0.110
Relative Concentration, C/Co
0.100
0.090
0.080
0.070
0.060
0.050
Kunia I - v5
0.040
Waipahu III - v5
0.030
Mililani I - v5
0.020
0.010
0.000
0
50000
100000
150000
200000
250000
300000
350000
Bed – Volumes
Breakthrough Limit
1%
5%
10%
Bed – Volumes Treated
140,670
187,400
217,190
GAC C Results
TCP Breakthrough Curve - GAC C
0.110
Relative Concentration, C/Co
0.100
0.090
0.080
0.070
0.060
Kunia I - v5
0.050
Waipahu III - v5
0.040
0.030
Mililani I - v5
0.020
0.010
0.000
0
50000
100000
150000
200000
250000
300000
350000
Bed – Volumes
Breakthrough Limit
1%
5%
10%
Bed – Volumes Treated
37,612
78,899
102,969
GAC D Results
TCP Breakthrough Curve - GAC D
0.110
Relative Concentration, C/Co
0.100
0.090
0.080
0.070
Kunia I - v5 (run 3)
0.060
Kunia I - v5 (run 8)
0.050
0.040
Waipahu III - v5
0.030
Mililani I - v5 (Outlier)
0.020
0.010
0.000
0
50000
100000
150000
200000
250000
300000
350000
Bed – Volumes
Breakthrough Limit
1%
5%
10%
Bed – Volumes Treated
152,793
203,849
236,359
GAC E Results
TCP Breakthrough Curve - GAC E
0.110
Relative Concentration, C/Co
0.100
0.090
0.080
0.070
0.060
Kunia I - v5
0.050
Waipahu III - v5
0.040
0.030
Mililani I - v5
0.020
0.010
0.000
0
50000
100000
150000
200000
250000
300000
350000
Bed – Volumes
Breakthrough Limit
1%
5%
10%
Bed – Volumes Treated
82,858
131,738
161,128
GAC F Results
TCP Breakthrough Curve - GAC F
0.110
Relative Concentration. C/Co
0.100
0.090
0.080
0.070
Kunia I - v5
0.060
0.050
Waipahu III - v5
0.040
0.030
Mililani I - v5
0.020
0.010
0.000
0
50000
100000
150000
200000
250000
300000
350000
Bed – Volumes
Breakthrough Limit
1%
5%
10%
Bed – Volumes Treated
113,114
164,223
195,610
GAC G Results
TCP Breakthrough Curve - GAC G
0.110
Relative Concentration. C/Co
0.100
0.090
0.080
0.070
Kunia I - v5
0.060
Waipahu III - v5
0.050
0.040
Mililani I - v5
0.030
0.020
0.010
0.000
0
50000
100000
150000
200000
250000
300000
350000
Bed – Volumes
Breakthrough Limit
1%
5%
10%
Bed – Volumes Treated
142,729
200,430
236,312
Kunia I Results
TCP Breakthrough Curve - Kunia I
TCP Concentration (ppb)
0.1
0.08
GAC A/B - v5
GAC C - v5
0.06
GAC D - v5 (run 3)
GAC D - v5 (run 8)
0.04
GAC E - v5
GAC F - v5
0.02
GAC G - v5
0
0
50000
100000
150000
200000
250000
300000
Bed – Volumes
Effectiveness
Best
Worst
GAC Type
A/B and D
C
350000
Waipahu III Results
TCP Breakthrough Curve - Waipahu III - v5
0.080
0.070
TCP Concentration (ppb)
0.060
GAC A/B - v5
0.050
GAC C - v5
0.040
GAC D - v5
0.030
GAC E - v5
GAC F - v5
0.020
GAC G - v5
0.010
0.000
0
50000
100000
150000
200000
250000
300000
Bed – Volumes
Effectiveness
Best
Worst
GAC Type
D and E
C
350000
Mililani I Results
TCP Breakthrough Curve - Mililani I
0.220
0.200
TCP Concentration (ppb)
0.180
0.160
0.140
GAC A/B - v5
0.120
GAC C - v5
0.100
GAC D - v5 (Outlier)
0.080
GAC E - v5
0.060
GAC F - v5
0.040
GAC G - v5
0.020
0.000
0
50000
100000
150000
200000
250000
300000
Bed – Volumes
Effectiveness
Best
Worst
GAC Type
A/B
C
350000
Comparative Analysis of Different GAC Types
Effectiveness of GAC by Water Source
Well
Most Effective
Least Effective
Kunia I
GAC A/B and D
GAC C
GAC D and E
GAC C
GAC A/B
GAC C
Waipahu III
Mililani I
Comparison of GAC Averages Among Different Water - Bed - Volumes
Carbon
Name
Flow Rate
(mL/min)
A/B
5.10
140,670
187,400
217,190
C
11.32
37,612
78,899
102,969
D
6.63
152,793
203,849
236,359
E
6.63
82,858
131,738
161,128
F
5.10
113,114
164,223
195,610
G
5.10
142,729
200,430
236,312
1% Breakthrough (BV) 5% Breakthrough (BV) 10% Breakthrough (BV)
Comparative Analysis of Different
GAC Types
Comparison of GAC Averages Among Different Water - ng TCP Mass Adsorbed per kg GAC Mass (ng/kg)
Carbon
Flow Rate
1% Breakthrough
5% Breakthrough
10% Breakthrough
Name
(mL/min)
(ng/kg)
(ng/kg)
(mg/kg)
5.10
A/B
354.0
461.5
521.6
C
11.3
64.4
150.9
205.5
D
6.63
216.2
287.1
329.3
E
6.63
282.4
436.5
524.5
F
5.10
293.1
409.9
484.0
G
5.10
390.6
524.4
607.0
Conclusions
 Key Findings from study:
 A method was developed to easily quantify 1 ppt of TCP
 All of the GACs can meet the possible new 5 ppt MCL
 In terms of bedvolumes treated:
 Kunia (A/B and D), Waipahu (D and E), Mililani (A/B and F-G)
 Using the average for all three waters: 1) D, 2) G, 3) A/B
 The currently used GAC unit in the field, GAC C, was by far the least
optimal GAC of the six tested
 In terms of total TCP adsorbed on average:
 The best GACs are 1) G, 2) A/B, 3) E
 We did not measure DBCP and EDB in this study.
 We only tested three well sites.