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From Bench to Full Scale:
A Water Utility’s Approach to
Compliance with the
California Hexavalent
Chromium MCLCraig Gorman, Corona Environmental ConsultingTarrah Henrie, California Water Service Company
Chad Seidel, Corona Environmental ConsultingLifei Huang, University of California Davis
Xue Li, University of California Davis
Overview
• Problem Description
• Regulatory Timeline
• Compliance Strategy
– Technology screening
– Bench, field, and pilot testing
– Equipment procurement
• Next Steps
Problem Description
• California Water Service Company (CalWater) operates two service areas where all groundwater supplies are impacted by the new Cr(VI) MCL– Service District A
• All 9 wells have Cr(VI) above the 10 µg/L MCL
– Service District B• All 8 wells have Cr(VI) above the 10 µg/L MCL
• Strong desire to have all sources remain in compliance with new MCL
Regulatory Timeline
• August 2013 – California Department of Public Heath issues the first in the nation hexavalent chromium [Cr(VI)] MCL
Action Date
California State Water Quality Control Board (SWQCB)
Department of Drinking Water (DDW) released draft Cr(VI)
MCL of 10 µg/L
August, 2013
DDW issued final Cr(VI) MCL rule package to Office of
Administrative Law (OAL)
April 15, 2014
OAL completed review and files regulation with Secretary
of State; regulation effective first day of following quarter
May 28, 2014
Cr(VI) MCL effective date July 1, 2014
Initiate monitoring within six months following the effective
date of the regulation (22CCR § 64432)
December 31, 2014
Quarterly monitoring:
Maintain rolling annual average less than 10.5 µg/L (Cr(VI)
with each sample result
(e.g. no more than 1 untreated sample for sources with
Cr(VI) >20 µg/L
March 31, 2015
June 30, 2015
September 30, 2015
Project Timeline
Occurring at 7 Sites
Initial
Technology
Screening
June2013
January 15January2014
June2014
Site specific and
Pilot-testing
Development of
Bid Documents
Equipment Supplier
Selection
Site Design &
Permitting
Construction
Begins
Q1 2015
Initial Technology Screening
• Water Supply Study• Non-treatment Alternatives• Primary Treatment Alternatives
– Strong Base Anion Exchange (SBA-IX)– Weak Base Anion Exchange (WBA-IX)– Reduction Coagulation Filtration (RCF)
• Other Treatment Alternatives– Reverse Osmosis– Biological Reduction Filtration– Adsorbent or Reductive Media
Initial Technology Screening
• Weak Base Anion Exchange (WBA-IX)– Raw water alkalinity and associated chemical addition yield high
operational costs
• Reduction Coagulation Filtration (RCF)– No sewer access for residual disposal – Large footprint– Intermittent well operation and limited opportunities for
centralization
• Strong Base Anion Exchange (SBA-IX)– Most appropriate technology based on conservative
performance estimates– Substantial cost saving can be recognized with improvements to
regeneration process
Strong Base Anion Exchange
(SBA-IX)
8
Strong Base Anion Exchange
Empty bed contact
time (EBCT)
Water quality
Re
sin
typ
e
Hydraulic loading rate
(HLR)
Compliance Strategy
Initial Field Testing
Initial Field Testing
• Chlorinated distribution system water
• Targeted HLR from 4 to 15 gpm/ft2
45 second EBCT
11
Initial Field Testing (Phase B)
• Columns redesigned with increased EBCT
– (2.25 min, 135 seconds)
– 2” dia column retrofitted tooperate as two columns inseries with intermediatesample point
• EBCT 45 sec and 90 sec
12
Initial Field Testing (Phase B)
0
5
10
15
20
25
0 5,000 10,000 15,000 20,000
Tota
l C
hro
miu
m (m
g/L
)
Throughput (Bed Volumes Treated)
HLR 12.7 gpm/ft2
HLR 8.2 gpm/ft2
HLR 5.3 gpm/ft2
HLR 3.7 gpm/ft2
LAB HLR
2.0gpm/ft2
Bench-Scale Testing – 2 Wells• EBCT 45
• Resin screening
(nitrate selective)
• Bicarbonate and
chloride
regeneration
Site-Specific Testing – 7 Wells
• Resin screening (4 resins)
• EBCT testing (45 sec – 135 sec)
• HLR testing (7.5 – 30 gpm/ft2)
Resin Selection
0
5
10
15
20
25
30
35
40
0 5,000 10,000 15,000 20,000 25,000 30,000
Tota
l C
hro
miu
m (m
g/L
)
Throughput (Bed Volumes)
Resin A, 135
Resin B, 135
Resin C, 135
Resin D, 135
Empty Bed Contact Time
0
5
10
15
20
25
30
35
40
0 5,000 10,000 15,000 20,000 25,000 30,000
Tota
l C
hro
miu
m (m
g/L
)
Throughput (Bed Volumes)
Resin A, 45
Resin A, 90
Resin A, 135
Hydraulic Loading Rate
0
5
10
15
20
25
30
35
40
0 5,000 10,000 15,000 20,000 25,000 30,000
Tota
l C
hro
miu
m (m
g/L
)
Throughput (Bed Volumes)
7.5 gpm/sq.ft.; 135 sec EBCT
15 gpm/sq.ft.; 135 sec EBCT
22.5 gpm/sq.ft.; 90 sec EBCT
30 gpm/sq.ft.; 45 sec EBCT
Raw (Min, Avg, Max)
Site-Specific Testing Results
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
50,000
District AWell 1
District AWell 2
District AWell 3
District BWell 1
District BWell 2
District BWell 3
District BWell 4
Be
d V
olu
me
s to
an
8 m
g/L
Th
resh
old
Resin A
Resin B
Resin C
Resin D
45sec EBCT 45 sec EBCT90 sec EBCT
135 sec EBCT
Pilot-Scale Testing - 2 Wells
• HLR investigation
• Bicarbonate and chloride
regeneration
• Optimization of chloride regeneration
Chloride Regeneration
0
10
20
30
40
50
60
70
80
90
100
0
100
200
300
400
500
600
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00
Chlo
ride
and
Sulfu
r Con
cent
ratio
n (g
/L)
Tota
l Chr
omiu
m C
oncn
etra
tion
(mg/
L)
Bed Volumes of Chloride Regenernant
Cr (Cycle 1)Cr (Cycle 2)Cl (Cycle 1)Cl (Cycle 2)S (Cycle 1)S (Cycle 2)
Bicarbonate Regeneration
0
5
10
15
20
25
0
10
20
30
40
50
60
0.00 2.00 4.00 6.00 8.00 10.00 12.00
Chlo
ride
and
Sulfu
r Con
cent
ratio
n (g
/L)
Tota
l Chr
omiu
m C
oncn
etra
tion
(mg/
L)
Bed Volumes of Bicarbonate Regenernant
Cr (Cycle 1)Cr (Cycle 2)Cl (Cycle 1)Cl (Cycle 2)S (Cycle 1)S (Cycle 2)
Segmented Regeneration
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
80,000
90,000
0
100
200
300
400
500
600
700
800
900
0 1 2 3 4 5 6 7 8 9 10
ClC
on
d, C
r
Projected waste volume with sulfate return = < 0.5 BV
Cond (mS/cm)
Cr tot (mg/L)
Cl (mg/L)
WasteRecovered
RinseSulfate Return Recovered
Brine
Impacts of Water Quality
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000
Su
lfa
te +
Nitra
te (
me
q/L
)
Throughput (Bed Volumes to 8 ug/L)
Sulfate + Nitrate
(meq/L)
Equipment Procurement
• To meet the compliance schedule, procurement had to begin before testing could be completed
• Developed performance based specification
– HLR, EBCT, regeneration requirements and brine disposal to be vendor defined
• Ultimate award based on life cycle costs
Cost Comparison
$-
$5.0
$10.0
$15.0
$20.0
$25.0
$30.0
$35.0
$40.0
Vendor 1 Vendor 2 Vendor 3 Vendor 4 Vendor 5
20
Ye
ar
NP
W
O&MCapital
Next Steps
• Complete local and state permitting
• Site improvements underway
• Treatment equipment is being fabricated
• Equipment expected to be operational early 2015
