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Optimizing Slime Control Chemical Feed in Tarrant
Regional Water Districts Raw Water PipelinesP. Greg Pope Ph.D., P.E.
Rob Cullwell P.E.
Jason Gehrig P.E. (TRWD)
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TRWD Raw Water Supply System
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Why feed chloramines?
Bio-Film Control
Zebra Mussel Mitigation
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Key Project Goals
• Richland Chambers and Cedar Creek– Improve chloramine feed efficiency– Protect intake conduit/towers– Improvements to existing chemical systems
• Benbrook – Design new chloramine feed system
• Sampling program to monitor chloramine decay• Quantify impacts of biofilm on pipeline friction
factor and power use
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Key Project Goals
• Richland Chambers and Cedar Creek– Improve chloramine feed efficiency– Protect intake conduit/towers– Improvements to existing chemical systems
• Benbrook – Design new chloramine feed system
• Sampling program to monitor chloramine decay• Quantify impacts of biofilm on pipeline friction
factor and power use
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Bench-Scale Testing
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Region 1Monochloramine
Formation
Region 2Monochloramine
Destruction
Region 3Free Chlorine
Residual
Tota
l Chl
orin
e &
Free
Am
mon
iaC
once
ntra
tions
More Chlorine AddedChlorine to Nitrogen (Cl2:N) Mass (Molar) Ratio
0 3 (0.6) 5 (1) 7.6 (1.5)
Breakpoint
Free Ammonia
Total Chlorine
DW
Proper Cl2/N ratio critical for chloramine stability
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Higher Cl2/N ratios increased chloramine decay
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 20 40 60 80 100
Mon
ochl
oram
ine
(mg/
L as C
l 2)
Time from sample collection (hours)
Cedar Creek pH 8.1
Richland Chambers pH 8.1
Benbrook pH 7.9
Notes:1) Water Source: Cedar Creek, Richland Chambers, Benbrook2) Date: 12/15/20143) Cl2:N ratio: 4.5:1 4) Simultaneous addition of chlorine and ammonia
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Higher Cl2/N ratio increases chloramine decay
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 20 40 60 80 100
Mon
ochl
oram
ine
(mg/
L as C
l 2)
Time from sample collection (hours)
Cedar Creek pH 7.6
Richland Chambers pH 8.1
Benbrook pH 7.9
Notes:1) Water Source: Cedar Creek, Richland Chambers, Benbrook2) Date: 12/15/20143) pH:ambient4) Cl2:N ratio: 5.5:1 (solid symbols); 4.5:1 (open symbols) 5) Simultaneous addition of chlorine and ammonia
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High Cl2/N ratio increases DBP formation
0
2
4
6
8
10
12
Cedar Creek Richland Chambers Benbrook
TTHM
Form
ation
(µg/
L)
4.5:1
5.5:1
Notes:1) 48 hour incubation2) pH ambient3) TOC: Cedar Creek = 5.8 mg/L; Richland
Chambers = 4.5 mg/L; Benbrook = 4.7 mg/L
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High Cl2/N ratio increases DBP formation
0
2
4
6
8
10
12
Cedar Creek Richland Chambers Benbrook
HAA5
Form
ation
(µg/
L)
4.5:1
5.5:1
Notes:1) 48 hour incubation2) pH ambient3) TOC: Cedar Creek = 5.8 mg/L; Richland
Chambers = 4.5 mg/L; Benbrook = 4.7 mg/L
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Proper pH critical for chloramine stability100
80
60
40
20Tota
l Com
bine
d C
hlor
ine
(%)
pH3 5 6 7 8
Trichloramine
Monochloramine
Dichloramine
Normal Range
9
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pH variability in source waters
5.0
6.0
7.0
8.0
9.0
10.0
11.0
8/11/1987 5/7/1990 1/31/1993 10/28/1995 7/24/1998 4/19/2001 1/14/2004 10/10/2006
pH
Date
RC (0.5m) CC (0.5m)*Note: Data from Jan 1990 to Mar 2008
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pH variability in source waters
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 10.5 11.0
Perc
ent n
ot Ex
ceed
ing (
%)
pH
RC (0.5m) CC (0.5m)*Note: Data from Jan 1990 to Mar 2008
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Higher pH decreases chloramine decay: Cedar Creek
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 5 10 15 20 25 30 35 40 45
Tota
l Chl
orin
e, M
onoc
hlor
amin
e Re
sidu
al (m
g/L)
Time (hours)
pH 7.0 Total ChlorinepH 7.0 MonochloraminepH 8.3 Total ChlorinepH 8.3 Monochloramine
Notes:1) Water Source: Cedar Creek2) Date: 8/26/20143) Cl2:N ratio: 4.5:14) Chloramine Dose: 5.0 mg/L5) Simultaneous addition of chlorine and ammonia
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Higher pH decreases chloramine decay: Richland Chambers
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 5 10 15 20 25 30 35 40 45
Tota
l Chl
orin
e, M
onoc
hlor
amin
e Re
sidu
al (m
g/L)
Time (hours)
pH 7.0 Total ChlorinepH 7.0 MonochloraminepH 8.3 Total ChlorinepH 8.3 Monochloramine
Notes:1) Water Source: Richland Chambers2) Date: 8/26/20143) Cl2:N ratio: 4.5:14) Chloramine Dose: 3.5 mg/L5) Simultaneous addition of chlorine and ammonia
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Full-Scale Testing
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Pipeline Sampling Locations
Waxahachie Pump Station
Richland-ChambersLake Pump
Station
Cedar CreekLake Pump
Station
Ennis Pump Station
Blackjack Road
Rosewood Ranch
NE 1036
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Chloramine Decay in the Pipeline: Cedar Creek
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 5 10 15 20 25
Tota
l Chl
orin
e, M
onoc
hlor
amin
e Re
sidu
al (m
g/L)
Time (hours)
Total Cl2 (hold)
NH2Cl (hold)
Total Cl2 (pipeline)
NH2Cl (pipeline)
Lake Pumpstation
Waxahachie
Rosewood Ranch
Ennis Pumpstation
Blackjack Road
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Chloramine Decay in the Pipeline: Richland Chambers
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 5 10 15 20 25
Tota
l Chl
orin
e, M
onoc
hlor
amin
e Re
sidu
al (m
g/L)
Time (hours)
Total Cl2 (hold)
NH2Cl (hold)
Total Cl2 (pipeline)
NH2Cl (pipeline)
Lake Pumpstation
Waxahachie
NE 1036
Ennis Pumpstation
Blackjack Road
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Chloramine loss from nitrification
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Chloramine loss from nitrification
Monitoring Parameters:• Monochloramine• Free ammonia• Nitrite• Nitrate
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Nitrification parameters measured in the pipeline: Cedar Creek
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0
0.5
1
1.5
2
2.5
3
3.5
4
PS RR Ennis BJ Wax
Cedar Creek
NH3
/Nitr
ite a
s N (m
g/L)
Tota
l Chl
orin
e/M
onoc
hlor
amin
e (m
g/L)
Total Cl (mg/L) Mono Chl (mg/L) NH3 (mg/L) Nitrite (mg/L)
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Nitrification parameters measured in the pipeline: Richland Chambers
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0
0.5
1
1.5
2
2.5
3
PS NE 1036 Ennis BJ Wax
Richland Chambers
NH3
/Nitr
ite a
s N (m
g/L)
Tota
l Chl
orin
e/M
onoc
hlor
amin
e (m
g/L)
Total Cl (mg/L) Mono Chl (mg/L) NH3 (mg/L) Nitrite (mg/L)
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Additional Pipeline Sampling Locations
Waxahachie Pump Station
Richland-ChambersLake Pump
Station
Cedar CreekLake Pump
Station
Mansfield
Kennedale Balancing Reservoir
Arlington Outlet
Midlothian
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Additional pipeline sampling: Cedar Creek
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
0
0.5
1
1.5
2
2.5
3
3.5
Pump Station
Waxahachie Midlothian Mansfield @ Church
KBR Arlington Outlet
NH3
/Nitr
ite/N
itrat
e as
N (m
g/L)
Tota
l Chl
orin
e/M
onoc
hlor
amin
e (m
g/L)
Total Chlorine Monochloramine Free Ammonia Nitrite Nitrate
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Additional pipeline sampling: Richland Chambers
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0
0.5
1
1.5
2
2.5
3
Pump Station
Waxahachie Midlothian Mansfield @ Church
KBR Arlington Outlet
NH3
/Nitr
ite/N
itrat
e as
N (m
g/L)
Tota
l Chl
orin
e/M
onoc
hlor
amin
e (m
g/L)
Total Chlorine Monochloramine Free Ammonia Nitrite Nitrate
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Chloramine Decay in the Pipeline: Richland Chambers – August 2015
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0 10 20 30 40 50
Tota
l Chl
orin
e Re
sidu
al (m
g/L)
Time (hours)
8/15 (hold)
8/15 (pipeline)Lake Pumpstation
Waxahachie
Ennis Pumpstation
Rosewood Ranch
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Chloramine Decay in the Pipeline: Richland Chambers – August 2015
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
0 10 20 30 40 50
Tota
l Chl
orin
e Re
sidu
al (m
g/L)
Time (hours)
8/15 (hold)
8/15 (pipeline)
9/11 (pipeline)
9/15 (pipeline)
Lake Pumpstation
Waxahachie
Ennis Pumpstation
Rosewood Ranch
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Test for Presence of Nitrifying Bacteria
0.2 micron filter
Pipeline water sample
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Nitrification evaluation in the Cedar Creek pipeline: Blackjack Road
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0 1 2 3 4 5 6 7 8 9
Nitr
ite/F
ree A
mm
onia
(mg/
L as N
)
Mon
ochl
oram
ine
(mg/
L as C
l 2)
Time from sample collection (days)
NH2Cl (mg/L)
NH3 (mg/L)
Nitrite (mg/L)
Notes:1) Dashed lines represent filtered sample (0.2 µm filter)
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Nitrification evaluation in the Cedar Creek pipeline: Blackjack Road
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0 1 2 3 4 5 6 7 8 9
Nitr
ite/F
ree A
mm
onia
(mg/
L as N
)
Mon
ochl
oram
ine
(mg/
L as C
l 2)
Time from sample collection (days)
Monochloramine (mg/L)Monochloramine (mg/L)NH3 (mg/L)Nitrite (mg/L)NH3 (mg/L)Nitrite (mg/L)
Notes:1) Dashed lines represent filtered sample (0.2 µm filter)
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Nitrification evaluation in the Richland Chambers pipeline: Blackjack Road
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
0 1 2 3 4 5 6 7 8 9
Nitr
ite/F
ree A
mm
onia
(mg/
L as N
)
Mon
ochl
oram
ine
(mg/
L as C
l 2)
Time from sample collection (days)
NH2Cl (mg/L) NH3 (mg/L)
Nitrite (mg/L)
Notes:1) Dashed lines represent filtered sample (0.2 µm filter)
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Nitrification evaluation in the Richland Chambers pipeline: Blackjack Road
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
0 1 2 3 4 5 6 7 8 9
Nitr
ite/F
ree A
mm
onia
(mg/
L as N
)
Mon
ochl
oram
ine
(mg/
L as C
l 2)
Time from sample collection (days)
Monochloramine (mg/L)Monochloramine (mg/L)NH3 (mg/L)Nitrite (mg/L)NH3 (mg/L)Nitrite (mg/L)
Notes:1) Dashed lines represent filtered sample (0.2 µm filter)
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Nitrification Control
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Nitrification Control
Nitrification Control → Inactivation > Growth
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Nitrification Control
Nitrification Control → Inactivation > GrowthOperational Controls• Chloramine Concentration
• Free ammonia concentration
• Residence time (reaction time)
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Nitrification Control
Nitrification Control → Inactivation > GrowthOperational Controls• Chloramine Concentration
• Free ammonia concentration
• Residence time (reaction time)
• Free Chlorination of Pipeline
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Conclusions
• Optimum chloramine formation conditions lead to – Reduced decay– Reduced DBP formation
• Significant nitrification occurring in the pipeline– Increased chloramine loss
• Demonstrated simple test for the presence of nitrifying bacteria
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Next Steps…..
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Contact Information
P. Greg Pope, Ph.D., P.E.Carollo [email protected]
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Extra Slides
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TTHM Formation
0
5
10
15
20
25
30
35
40
45
50
0 5 10 15 20 25 30 35
TTHM
(µg/
L)
Time (minutes)
Cedar Creek
Richland Chambers
Benbrook
Notes:1) Samples collected 9/4/20142) pH: Cedar Creek - 7.5
Richland Chambers - 7.8Benbrook - 8.1
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Historical LSI – Raw Water
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0
Perc
ent n
ot Ex
ceed
ing (
%)
LSI
Cedar Creek Reservoir Richland Chambers Reservoir Benbrook Reservoir
Notes: 1) Data from Jan 1990 to Mar 2008 (depth
ranges from 3-6m)2) Data obtained from Appendix A of Water
Quality Analysis Technical Memorandum (RPS Espey)
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Caustic currently fed to Cedar Creek for Corrosion control
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
-1.500 -1.000 -0.500 0.000 0.500 1.000 1.500
Perc
ent n
ot Ex
ceed
ing (
%)
LSI
Cedar Creek Intake Cedar Creek Treated
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DBP formation testing
0
2
4
6
8
10
12
14
16
18
20
Waxahachie (10 hours)
Lake Pump Station Hold (22 hours)
Bench (22 hours)
Waxahachie (13 hours)
Lake Pump Station Hold (22 hours)
Bench (22 hours)
TTHM
(µg/
L); H
AA5
(µg/
L); N
DMA
(ng/
L)TTHM
HAA5
NDMA
Total Chlorine Demand
Notes:1) Samples collected 9/4/20142) Bench testing - Chlorine and ammonia added
simultaneously at a 4.5:1 Cl2:N ratio3) NDMA detection limit = 2 ng/L
Richland Chambers Cedar Creek
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High Cl2/N ratio increases DBP formation
0
2
4
6
8
10
12
14
Cedar Creek Richland Chambers Benbrook
NDM
A Fo
rmati
on (n
g/L)
4.5:1
5.5:1
Notes:1) 48 hour incubation2) pH ambient3) TOC: Cedar Creek = 5.8 mg/L; Richland
Chambers = 4.5 mg/L; Benbrook = 4.7 mg/L