Cyanogen bromide (CNBr) formation in
drinking water from water sources with
elevated bromide concentrations
A.-M. Tugulea, R. Aranda-Rodriguez, M. Giddings, F. Lemieux, J. Hnatiw
Health Canada, Ottawa, Canada
Background
•
The enhanced formation of nitrogen-containing disinfection by-products
(N-DBPs), including cyanogens (CNCl and CNBr), is well documented in
WTPs in which chloramines are used for secondary disinfection.
•
In 2009-2010, a National Survey of DBPs was conducted. Although
some WTP had source water with high bromide content, cyanogen
bromide (CNBr) was not analysed due to the lack of an available
analytical method at the time.
•
In Canada, few treatment plants monitor CNCl and CNBr
concentrations.
2
Background (cont.): National Survey of
Disinfection By-Products (2009-2010) Findings:
Higher concentrations of CNCl were formed in systems using chloramine.
90
Percentage of Facilities
80
70
60
50
40
30
20
10
0
Chlorination- T
Chlorination- D2
Chloramination- T
Chloramination- D2
Range of CNCl Concentration for Winter Samples
3
Current Study:
•
The present study was designed to develop an analytical method for
cyanogen bromide (CNBr), to be used in future surveys.
•
An in-house method for the analysis of DBPs in source water and drinking
water was modified to include CNBr.
•
CNBr was determined for 16 WTPs included in the Targeted survey of
emerging disinfection by-products, in drinking water from WTPs using a high
salinity source water.
•
Contribution of CNBr to total cyanogen concentration in drinking water was
assessed.

Total cyanogen is defined as the sum of the two cyanogen compounds with
the highest expected concentrations: CNCl and CNBr
•
The survey targeted WTPs where enhanced iodo-THM and/or nitrosamine
formation was expected.
•
Chloramines were expected to be formed in all WTPs included in the study.
4
Current Study:
•
In the National Survey data, the highest Br- concentrations (>100
µg/L) were typically found in source waters with Na+ concentrations
>20 mg/L
•
CNBr was expected to be formed from source waters with increased
Br- concentration.
•
Participating WTPs were chosen for high Na+ concentrations and
the presence of ammonium in the source water .
•
Cyanogen compounds are known to be more stable in the presence
of chloramines then in the presence of free chlorine.
5
Current Study: Design
•
16 WTPs in two Canadian Provinces, with source water DOC ranging
from 0.62 mg/l to 17 mg/L.
•
Na+ concentrations in source water ranged from 10 mg/L to 760 mg/L
 10 systems have Na+ concentrations >200 mg/L.
•
Source water has naturally occurring NH4+ ranging from <0.05 mg/L to
2.7 mg/L.
•
All WTPs in the study use ammonium in the treatment train and/or have
naturally occurring ammonium.
•
This study also investigated other potential disinfection by-products and
water contaminants: THMs; HANs; HA; CNCl; iodo-THMs, nitrosamines,
bromate, and perchlorate.
6
Study locations: map
7
Sampling and Analytical Method for CNBr
•
Sampling protocol: 65 mL brown glass bottles; no headspace, 0.114 M
ascorbic acid for quenching; pH lowered to 4.5 using 1.0 N HCl.
•
Samples were collected for raw water, treated water and mid-point
distribution water, during winter and summer sampling campaigns.
•
•
All samples were collected and analysed in duplicate.
•
Analytical Standard: 1 ml ampule of 2000µg/mL CNBr in acetone (Purity:
97%), custom manufactured by SPEX Certiprep, through the offices of
Caledon Laboratories.
•
•
Stock Solution: diluted Analytical Standard to 1000µg/mL in acetone.
Sample shipping and storage: samples were shipped and stored between
00C - 100C and analysed within 72 hours from collection.
Spiking Standard: diluted Stock to 10µg/mL in MTBE
8
Analytical Method
•
The in-house liquid-liquid extraction GC-ECD method for neutral DBPs,
based on EPA Method 551.2, was modified to include CNBr (Figure 1).
•
Dual Column confirmation: » RT on DB-5: 4.87 min and
» RT on DB-1: 5.75 min
MDL= 0.06 µg/L.
•
•
•
We considered the MDL adequate for determinations of CNBr from
drinking water, based on previous exposure data.
The modified method was preferred to other analytical alternatives tested
in our laboratory (e.g. SPME-GC-MS) due to:



convenience of determining 29 neutral DBPs using the same analytical
procedure
no additional sample required (used same sample)
very little extra cost
9
Analytical Method
Fig. 1: Chromatogram of raw and treated water extracts from site 8,
analysed using a DB5 column, showing CNCl and CNBr peaks
10
Results: concentration range and contribution
to total cyanogen
Table 1. CNCl and CNBr concentration range and contribution to Total cyanogen
CNCl conc.
CNBr conc.
(MDL=0.07 µg/L)
(MDL=0.06 µg/L)
14/16
10/16
Maximum conc. detected
3.1
1.7
Average conc. for treated water /summer
0.72
0.20
Average conc. for treated water /winter *
0.76
0.13
Median conc. for treated water /summer
0.46
0.07
Median conc. for treated water /winter *
0.35
0.07
Max % contribution to Total cyanogen
100
86.1
No. of sites where the analyte was detected
* A number of WTPs were not sampled during winter
11
Results: concentration range and contribution
to total cyanogen
Fig. 2. CNCl and CNBr concentrations
in treated water/summer
3.5
100.0
CNCl
90.0
3
Concentration [µg/L]
Fig. 3. CNCl and CNBr % contribution to
Total cyanogen in treated water/summer.
CNBr
80.0
2.5
70.0
60.0
2
50.0
1.5
40.0
30.0
1
20.0
0.5
10.0
0.0
0
2
3
4
5
6
7
8
9 10 11 12 13 14 15
Site Location
2
3
4
5
6
7
8
9 10 11 12 13 14 15
Site Location
%Max CNCl
%Max CNBr
12
Results: concentration range and contribution
to total cyanogen
Fig. 4. CNCl and CNBr concentrations
in treated water/winter.
100.0
2.50
2.00
Concentration [µg/L]
Fig. 5. CNCl and CNBr % contribution to
Total cyanogen in treated water/winter.
CNCl
90.0
CNBr
80.0
70.0
60.0
1.50
50.0
40.0
1.00
30.0
20.0
0.50
10.0
0.0
0.00
3
4
5
6
8
11 12 13 14 15 16 17
Site Location
3
4
5
6
8
11 12 13 14 15 16 17
Site Location
%Max CNCl
%Max CNBr
13
Discussion:
•
Although most facilities included in the study use chlorine as a primary
disinfection agent, all of them have naturally present ammonium,
resulting in the formation of chloramines during disinfection.
•
Total cyanogen concentrations were in the range expected to be found
in drinking water plants using chloramines, based on previous studies
and published data.
•
Measured CNBr concentrations ranged from below the MDL (0.06
µg/L) to 1.7 µg/L.
•
Results obtained for CNBr were in the same range as results
determined in this study for CNCl (Figures 2 and 4).
14
Discussion (cont.):
•
The highest total cyanogen concentrations were found in the finished
water and under winter conditions, confirming the formation patterns
known for CNCl from the scientific literature
•
At some sites, the contribution of CNBr to total cyanogen was found to
be very large (Figures 3 and 5).
•
The highest contribution of CNBr to total cyanogen was found to be
86% in a treated water sample collected in the winter of 2012.
15
Conclusions
•
Drinking water disinfection by-products (DBPs) can include several
compounds with cyanogen-related structure, some of which may have
possible health concerns.
•
Determining only CNCl may lead to an underestimate of the total
cyanogen-based DBPs and, consequently, to an underestimate of the
potential risk to humans.
•
Our results prove that CNBr can, in fact, be formed in some WTPs at
concentrations that are in the same range as those of CNCl and
sometimes, under “ideal” conditions, even exceed those
concentrations.
16
Conclusions:
•
Total cyanogen (i.e., CNCl and CNBr), should be analysed to help
ensure the selection of the most appropriate treatment process and
operating parameters to remove or prevent formation of these DBPs.
•
The addition of CNBr to the existing multi-analyte method for
determining neutral DBPs from drinking water samples (based on EPA
Method 551.2) makes this inexpensive and convenient.
•
The new addition to our list of analytical methods provides a valuable
tool in the study of N-DBPs, specifically, total cyanogen formation, and
will be added to future surveys.
17
Acknowledgements
•
Data presented here were collected as part of the Targeted Survey
of Selected Disinfection By-Products in source waters with high
saline concentrations, a 3 year study funded by the Health Canada
Monitoring and Surveillance Fund as part of the Chemical
Management Plan (CMP).
•
The authors would like to thank the members of the FederalProvincial-Territorial Committee on Drinking Water for their gracious
help in providing data for the site selection and the water plant
operators for agreeing to participate in the study.
•
The authors would like to thank Ashley Cabecinha and Zhiyun Jin
for their technical support.
18
References
•
U.S. EPA. 1985b. Drinking Water Criteria Document for Cyanide. Prepared by
the Office of Health and Environmental Assessment, Environmental Criteria and
Assessment Office, Cincinnati, OH for the Office of Drinking Water, Washington,
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•
Na C, Olson TM. Stability of cyanogen chloride in the presence of free chlorine
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Chlorination/Chloramination of Primary Amines.2007. Environ. Sci. Technol.
2007, 41, 1288-1296
•
Heller-Grossman, L.; Idin, A.; Limoni-Relis, B.; Rebhun, M. Formation of
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Lake Water.1999.Environ. Sci. Technol., 33 (6), pp 932–937.
•
B. Cancho, F. Ventura, M.T. Galceran, Simultaneous determination of cyanogen
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