TWCA Annual Convention: Optimizing Slime Control Chemical Feed in TRWD Raw Water Pipelines, Greg Pope

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Optimizing Slime Control
Chemical Feed in Tarrant
Regional Water Districts Raw
Water Pipelines
P. Greg Pope Ph.D., P.E.
Rob Cullwell P.E.
Jason Gehrig P.E. (TRWD)

3
TRWD Raw Water Supply System

4
Why feed chloramines?
Bio-Film Control
Zebra Mussel Mitigation

5
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

6
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

7
Bench-Scale Testing

8
Region 1
Monochloramine
Formation
Region 2
Monochloramine
Destruction
Region 3
Free Chlorine
Residual
TotalChlorine&
FreeAmmonia
Concentrations
More Chlorine Added
Chlorine 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

9
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
Monochloramine(mg/LasCl2)
Time fromsample collection(hours)
Cedar Creek pH 8.1
Richland Chambers pH 8.1
Benbrook pH 7.9
Notes:
1) Water Source:CedarCreek,RichlandChambers,Benbrook
2) Date:12/15/2014
3) Cl2:N ratio: 4.5:1
4) Simultaneousadditionof chlorine and ammonia

10
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
Time fromsample collection(hours)
Cedar Creek pH 7.6
Richland Chambers pH 8.1
Benbrook pH 7.9
Notes:
1) Water Source:CedarCreek,RichlandChambers,Benbrook
2) Date:12/15/2014
3) pH:ambient
4) Cl2:N ratio: 5.5:1 (solid symbols);4.5:1 (opensymbols)

11
High Cl2/N ratio increases DBP formation
0
2
4
6
8
10
12
Cedar Creek Richland Chambers Benbrook
TTHMFormation(µg/L)
4.5:1
5.5:1
Notes:
1) 48 hour incubation
2) pH ambient
3) TOC: CedarCreek= 5.8 mg/L; Richland
Chambers= 4.5 mg/L;Benbrook= 4.7 mg/L

12
0
2
4
6
8
10
12
HAA5Formation(µg/L)
4.5:1
5.5:1
Notes:
2) pH ambient

13
Proper pH critical for chloramine stability
100
80
60
40
20
TotalCombinedChlorine(%)
pH
3 5 6 7 8
Trichloramine
Monochloramine
Dichloramine
Normal Range
9

14
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

15
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
PercentnotExceeding(%)
pH
RC (0.5m) CC (0.5m)
*Note: Data from Jan 1990 to Mar 2008

16
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
TotalChlorine,MonochloramineResidual(mg/L)
Time (hours)
pH 7.0 Total Chlorine
pH 7.0 Monochloramine
Notes:
1) Water Source:CedarCreek
2) Date:8/26/2014
3) Cl2:N ratio: 4.5:1
4) Chloramine Dose:5.0 mg/L

17
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
Time (hours)
Notes:
1) Water Source:Richland Chambers
2) Date:8/26/2014
3) Cl2:N ratio: 4.5:1
4) Chloramine Dose:3.5 mg/L

18
Full-Scale Testing

19
Pipeline Sampling Locations
Waxahachie Pump Station
Richland-Chambers
Lake Pump Station
Cedar Creek
Lake Pump Station
Ennis Pump Station
Blackjack Road
Rosewood Ranch
NE 1036

20
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
Time (hours)
Total Cl2 (hold)
NH2Cl(hold)
Total Cl2 (pipeline)
NH2Cl(pipeline)
LakePumpstation
Waxahachie
Rosewood Ranch
Ennis Pumpstation
Blackjack Road

21
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
Time (hours)
Total Cl2 (hold)
NH2Cl(hold)
Total Cl2 (pipeline)
NH2Cl(pipeline)
LakePumpstation
Waxahachie
NE1036
Ennis Pumpstation
Blackjack Road

22
Chloramine loss from nitrification

23
Chloramine loss from nitrification
Monitoring Parameters:
• Monochloramine
• Free ammonia
• Nitrite
• Nitrate

24
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/NitriteasN(mg/L)
TotalChlorine/Monochloramine(mg/L)
Total Cl (mg/L) Mono Chl (mg/L) NH3 (mg/L) Nitrite (mg/L)

25
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/NitriteasN(mg/L)
Total Cl (mg/L) Mono Chl (mg/L) NH3 (mg/L) Nitrite (mg/L)

26
Additional Pipeline Sampling Locations
Waxahachie Pump Station
Richland-Chambers
Lake Pump Station
Cedar Creek
Lake Pump Station
Mansfield
Kennedale
Balancing
Reservoir
Arlington Outlet
Midlothian

27
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/Nitrite/NitrateasN(mg/L)
Total Chlorine Monochloramine Free Ammonia Nitrite Nitrate

28
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/Nitrite/NitrateasN(mg/L)
Total Chlorine Monochloramine Free Ammonia Nitrite Nitrate

29
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
TotalChlorineResidual(mg/L)
Time (hours)
8/15 (hold)
8/15 (pipeline)
Lake Pumpstation
Waxahachie
Ennis Pumpstation
Rosewood Ranch

30
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
TotalChlorineResidual(mg/L)
Time (hours)
8/15 (hold)
8/15 (pipeline)
9/11 (pipeline)
9/15 (pipeline)
Lake Pumpstation
Waxahachie
Ennis Pumpstation
Rosewood Ranch

31
Test for Presence of Nitrifying Bacteria
0.2 micron filter
Pipeline water sample

32
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
Nitrite/FreeAmmonia(mg/LasN)
Time fromsample collection(days)
NH2Cl(mg/L)
NH3 (mg/L)
Nitrite (mg/L)
Notes:
1) Dashedlinesrepresentfilteredsample (0.2µm filter)

33
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
Monochloramine(mg/L)
NH3 (mg/L)
Nitrite (mg/L)
NH3 (mg/L)
Nitrite (mg/L)
Notes:

34
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
NH2Cl(mg/L) NH3 (mg/L)
Nitrite (mg/L)
Notes:

35
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
NH3 (mg/L)
Nitrite (mg/L)
NH3 (mg/L)
Nitrite (mg/L)
Notes:

36
Nitrification Control

37
Nitrification Control → Inactivation > Growth

38
Operational Controls
• Chloramine Concentration
• Free ammonia concentration
• Residence time (reaction time)

39
Operational Controls
• Chloramine Concentration
• Free ammonia concentration
• Residence time (reaction time)
• Free Chlorination of Pipeline

40
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

41
Next Steps…..

42
Contact Information
P. Greg Pope, Ph.D., P.E.
Carollo Engineers
gpope@carollo.com
512.453.5383

43
Extra Slides

44
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 9/4/2014
2) pH: Cedar Creek - 7.5
Richland Chambers - 7.8
Benbrook - 8.1

45
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
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)

46
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
LSI
Cedar Creek Intake Cedar Creek Treated

47
DBP formation testing
0
2
4
6
8
10
12
14
16
18
20
Waxahachie
(10 hours)
LakePump
Station Hold
(22 hours)
Bench (22
hours)
Waxahachie
(13 hours)
LakePump
Station Hold
(22 hours)
Bench (22
hours)
TTHM(µg/L);HAA5(µg/L);NDMA(ng/L)
TTHM
HAA5
NDMA
Total Chlorine Demand
Notes:
1) Samplescollected9/4/2014
2) Benchtesting - Chlorine and ammoniaadded
simultaneously ata 4.5:1 Cl2:N ratio
3) NDMA detectionlimit = 2 ng/L
Richland Chambers Cedar Creek

48
0
2
4
6
8
10
12
14
NDMAFormation(ng/L)
4.5:1
5.5:1
Notes:
2) pH ambient

TWCA Annual Convention: Optimizing Slime Control Chemical Feed in TRWD Raw Water Pipelines, Greg Pope

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TWCA Annual Convention: Optimizing Slime Control Chemical Feed in TRWD Raw Water Pipelines, Greg Pope