bromate formation in ozone disinfection systems. ndwrri... · goal and objectives goal quantify the...
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Leslee Storlie M.S. Environmental Engineering : NDSU
Dr. Wei Lin Research Advisor: NDSU
February 7th, 2013: North Dakota WRRI
Outline Moorhead WTP
Bromate
Goal and Objectives
Source Water Bromide
Bromate Formation
Influential Parameters
Conclusions
Moorhead WTP Capacity: 10 MGD
Serves about 40,000 people; City of Moorhead, City of Dilworth, and Oakport Township
Treatment Process:
Bromate (BrO3-)
Disinfection byproduct
Oxidized form of bromide (Br-), a component found naturally in many source waters
Forms in ozone (O3) disinfection process
Br- + O3 BrO3-
Possible carcinogen and monitored by EPA
MCL of 10 ppb
Bromate Influential Parameters Proportional to: bromide and ozone dose
Influenced by:
pH:
Increases in pH, increased bromate formation
Most studies considered pH values between 6.0 and 8.5
Temperature:
Increases in temperature, increased bromate formation
Increases in reaction kinetics
Organics:
Increases in organic content, decreased bromate formation
Goal and Objectives Goal
Quantify the bromate formation in the disinfection process and identify operational strategies to minimize bromate formation
Objectives Determine bromide concentrations in the source waters
Study bromate formation in the ozonation process
Evaluate the impact of operational parameters on bromate formation
Determine controlling options and procedures for reducing bromate formation
Surface Water Source
0
5
10
15
20
25
30
0.00
2.00
4.00
6.00
8.00
10.00
12.00
14.00
16.00
11/3/2011 12/23/2011 2/11/2012 4/1/2012 5/21/2012 7/10/2012 8/29/2012 10/18/2012 12/7/2012 1/26/2013
Tem
per
atu
re (
°C)
TO
C (
mg
/L)
Date (mm/dd/yyyy)
TOCTemperature
Red River
Primary water source
Subject to seasonal variations in temperature and quality
Surface Water Bromide Summary
Bromide remained relatively low
Bromide concentration varied between 0.03 and 0.07 ppm
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
0.20
4/1/12 7/10/12 10/18/12 1/26/13
Bro
mid
e (p
pm
)*
Date (mm/dd/yy)
*Courtesy of Fargo WTP
Groundwater Sources Buffalo Aquifer
Shallow, unconfined
High in hardness
Moorhead Aquifer
Slowly recharged confined aquifer
Relatively low hardness
Bromide concentrations not tested before this study
Groundwater Bromide
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
Well 6 Well 6B Well 8 Well 9 Well 10 Well 1 Well 2
Ave
rag
e B
rom
ide
(pp
m)
Buffalo Aquifer
Moorhead Aquifer
Summary
Moorhead Aquifer averaged 0.30 ppm
Buffalo Aquifer averaged 0.07 ppm
The deeper, slowly recharged, Moorhead Aquifer had much higher bromide concentrations
Source Water Bromide Red River Groundwater
Relatively low in concentration
Averaged 0.05 ppm
Buffalo Aquifer
Relatively low in concentration
Averaged 0.07 ppm
Moorhead Aquifer
Relatively high in concentration
Averaged 0.30 ppm
Red River Br- < Buffalo Aquifer Br- < Moorhead Aquifer Br-
Well and River Flow
0
1000
2000
3000
4000
5000
6000
4/1/2012 5/21/2012 7/10/2012 8/29/2012 10/18/2012 12/7/2012 1/26/2013
Flo
w (
gp
m)
Date (mm/dd/yyyy)
Well Flow
River Flow
Total Flow
Ozone Disinfection Section 1: Taste and odor removal
Section 2 and 3: Disinfection credits
Bromate Formation
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
2/11/2012 4/1/2012 5/21/2012 7/10/2012 8/29/2012 10/18/2012 12/7/2012 1/26/2013
Bro
mat
e (p
pb
)
Date (mm/dd/yyyy)
Section 1Section 2Section 3MCL
Temperature Influence
0
5
10
15
20
25
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
2/11/2012 4/1/2012 5/21/2012 7/10/2012 8/29/2012 10/18/2012 12/7/2012 1/26/2013
Tem
per
atu
re (
°C)
Bro
mat
e (p
pb
)
Date (mm/dd/yyyy)
Total Bromate
Finished Water Temp
Sample Water Temp
pH Influence
8
9
10
11
12
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
2/11/2012 4/1/2012 5/21/2012 7/10/2012 8/29/2012 10/18/2012 12/7/2012 1/26/2013
pH
Bro
mat
e (p
pb
)
Date (mm/dd/yyyy)
Total Bromate
Section 1 pH
Section 2 pH
Section 3 pH
Organic Content Influence
0.0
1.0
2.0
3.0
4.0
5.0
6.0
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
2/11/2012 4/1/2012 5/21/2012 7/10/2012 8/29/2012 10/18/2012 12/7/2012 1/26/2013
TO
C (
mg
/L)
Bro
mat
e (p
pb
)
Date (mm/dd/yyyy)
Total Bromate
Influent TOC
Influent Bromide Influence
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
2/11/2012 4/1/2012 5/21/2012 7/10/2012 8/29/2012 10/18/2012 12/7/2012 1/26/2013
Bro
mid
e (p
pm
)
Bro
mat
e (p
pb
)
Date (mm/dd/yyyy)
Total Bromate
Influent Bromide
Bromate Formation
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
2/11/2012 4/1/2012 5/21/2012 7/10/2012 8/29/2012 10/18/2012 12/7/2012 1/26/2013
Bro
mat
e (p
pb
)
Date (mm/dd/yyyy)
Section 1Section 2Section 3MCL
August 3, 2012
River Water Quality August 3rd, 2012
Rain event after a very dry summer
River quality became poor Increased hardness and
TOC
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
7/30 7/31 8/1 8/2 8/3 8/4 8/5 8/6 8/7 8/8 8/9 8/10 8/11
TO
C (
mg
/L)
2012 Date (m/dd)
0
50
100
150
200
250
300
350
400
450
500
7/30 7/31 8/1 8/2 8/3 8/4 8/5 8/6 8/7 8/8 8/9 8/10 8/11
Har
dn
ess
(mg
/L a
s C
aCO
3)
2012 Date (m/dd)
Total HardnessNon-Carbonate HardnessCalcium Hardness
Control Changes Done to assist treatment
process with river quality changes
Add well flow and decrease river flow
Increase ozone dose
River and Well Flow Changes
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
7/30/12 8/1/12 8/3/12 8/5/12 8/7/12 8/9/12 8/11/12
Ozo
ne
Infl
uen
t B
rom
ide
(pp
m)
Date (mm/dd/yy)
0
500
1000
1500
2000
2500
3000
7/30/12 8/1/12 8/3/12 8/5/12 8/7/12 8/9/12 8/11/12
Flo
w (
gp
m)
Date (mm/dd/yy)
River
Well
Wells 6B and 9
Ozone Dose Changes
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
7/30/12 8/1/12 8/3/12 8/5/12 8/7/12 8/9/12 8/11/12
Ozo
ne
Do
se (
mg
/L)
Date (mm/dd/yy)
0.0
2.0
4.0
6.0
8.0
10.0
12.0
7/30/12 8/1/12 8/3/12 8/5/12 8/7/12 8/9/12 8/11/12
CT
Rat
io (
Act
ual
/Req
uir
ed)
Date (mm/dd/yy)
Conclusions Bromate formation is a concern at the Moorhead WTP
The highest bromate concentrations occurred in the summer months
Variations in bromate formation from day to day are influenced by the operation of the treatment plant
Bromate formation can be controlled through changes in operational control methods
Thank you!
Questions?