&EPA
United States
Environmental Protection
Agency
EPA/600/S-17/165
June 2017
www.epa.gov/research
Free Chlorine and Cyanuric
Acid Simulator Application
Description - Version 0.50
Office of Research and Development
National Risk Management Research Laboratory
Water Systems Division
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Free Chlorine and Cyanuric Acid Simulator
Application Description - Version 0.50 - May 10,2017
INTRODUCTION
A web-based application (WBA) has been developed to simulate the water chemistry
associated with the free chlorine and cyanuric acid system (i.e., chlorinated cyanurates). The
WBA can be accessed at https://iisepaord.shinYapps.io/cYaniiric/ (all lowercase).
The WBA is freely accessible, providing drinking water practitioners (e.g., operators,
regulators, engineers, professors, and students) a tool to explore the water chemistry of the free
chlorine and cyanuric acid system and to estimate free chlorine concentrations in an interactive
manner without requiring proprietary software or modeling expertise. The WBA allows the user
to specify two side-by-side simulations, providing a direct comparison of impacts associated
with changing initial conditions (e.g., free chlorine, cyanuric acid, Dichlor, and Trichlor
concentrations and pH). Once completed, the user may download simulation data to use offline.
The WBA allows the user to estimate the free chlorine concentration when cyanuric acid
is present as is the case when adding chlorine-containing chemicals commonly referred to as
Dichlor (anhydrous sodium dichloroisocyanurate or sodium dichloroisocyanurate dihydrate) or
Trichlor (trichloroisocyanuric acid) to drinking water systems. The tool is based on the
equilibrium model presented by O'Brien (1972) and O'Brien et al (1974) for 25°C. Note that
currently no information is available at temperatures other than 25°C, and the user must be aware
of this fact when operating at different temperatures as simulated concentration may differ.
1
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FREE CHLORINE AND CYAN URIC ACID APPLICATION
The WBA is self-contained and provides the necessary information to direct the user on
how to conduct a simulation, providing guidance through pop-up boxes that appear when
hovering a screen pointer over a required input or possible selection (Figure 1).
Conditions for Chemical Speciation Plots
pH Range
Set slider to known added free
chlorine concentration in mg
per liter as chlorine. If this is a
drinking water sample, the free
chlorine DPD measurement
should be entered as this
represents the total chlorine in
the drinking water sample
because of known free chlorine
DPD method interferences (see
Application Documentation).
Chemical Addition Sea
Free Chlorine as chlorine
Added Free Chlorine Concentration (mg CI2.''L)
o
b
14
"i r
hs itself (129.07 MW) -
10
Figure 1 Example tooltip pop-up box
The WBA consists of several areas described below in detail: header, simulation input,
plot preferences, and output plot.
Header area. The top of the WBA's web page contains a header area (Figure 2) where
general information about the WBA is presented along with hyperlinks to the main research
article used in creating the WBA and the Application Documentation (i.e., this document).
2
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Free Chlorine and Cyanuric Acid System Simulator
Version 0.50, last Updated May 10, 2017
Created by David 6, Wahman (wahman.davki@epa.gov}, United Slates Environmental Protection Agency
The provided application simulates the water chemistry, a .hicrinated cyanurates). The application
allows the user to estimate the free chlorine concentration ommonly referred to as Dichlor
(anhydrous sodium dichloroisocyanurate or sodium dichlo sons and associated constants are for a
temperature of 25 degrees Ceisius as presented by Qbrien ei 31 .¦ :¦ ¦¦¦ ¦ ¦¦¦ . ¦
To open a document describing the application in a new window, click on the following fink ¦"s;xvi v.v > -\.\x
The application was developed by the United States Environmental Protection Agency (EPA). Mo warranty expressed or implied is made regarding the accuracy or utility of the system, nor
shaii the act of distribution constitute any such warranty. EPA has relinquished control of the information and no longer has responsibility to protect the integrity, confidentiality, or availability
of the information . Arty reference to specific commercial products , processes, or services by service mark, trademark, manufacturer, or otherwise, does not constitute or imply their
er "1= n i ti > {c v. t ¦» ^ >\ UEM h ] } p p n ^ i j r ->r, "p i ^ r - ict i n it rl d e r i i k t L' or me
United States Government The views expressed m this application do not necessarily represent the views or policies of the EPA Although a reasonable effort has been made to assure
th 1 i i r ^ ifi 01 s 3i. it' (i ^ ^ -i " °\ 1- nitr tu I _ j ^ r J' ti c1 r f ijc i a i u whoisucvci iui e i I r any use
Figure 2 Header area
Simulation input area. Below the header area is the simulation input area where the
user selects and inputs the desired variables required to conduct simulations (Figure 3). In the
simulation input area, the user selects the simulation pH range. The default range is set to pH 6
to 11, representing a range that would cover drinking water, but the user is free to select any
range from pH 0 to 14 to further explore the water chemistry.
The user may select from seven different chemical addition scenarios which correlate to
the chemical speciation immediately after adding the following combination of chemicals to
water without accounting for any chlorine demand present in the water:
1. Free chlorine as chlorine and cyanuric acid as itself,
2. Anhydrous sodium dichloroisocyanurate as chlorine,
3. Anhydrous sodium dichloroisocyanurate as itself,
4. Sodium dichloroisocyanurate dihydrate as chlorine,
5. Sodium dichloroisocyanurate dihydrate as itself,
6. Trichloroisocyanuric acid as chlorine, or
7. Trichloroisocyanuric acid as itself.
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Depending on the scenario selected, the options for entering chemical concentrations will
change accordingly. When entering chemical concentrations "as itself', the WBA assumes that
the chemical has a 100% purity. For each chemical addition scenario, the WBA uses the entered
chemical concentrations to determine the total chlorine (TOTC1) and total cyanurate (TOTCy)
concentrations to use in the simulations.
In addition to simulating the immediate speciation after direct addition of the various
chemicals, the free chlorine and cyanuric acid scenario can also be used to simulate conditions
and estimate the free chlorine concentration for water samples where chlorine demand has
decreased the initial amount of TOTC1 added to the water. In this case, the free chlorine
concentration entered is the measured free chlorine concentration obtained from the free chlorine
DPD (e.g., HACH Company, 2014a) or amperometric titration (APHA et al, 2005) methods
which will actually provide the TOTC1 concentration in the water because of known method
interferences (Wajon & Carrell Morris, 1980; Whittle, 1970). The user will also need to know or
estimate the TOTCy concentration where the sample was taken to enter in for the cyanuric acid
concentration.
In drinking water, TOTCy concentrations are generally less than the available method
detection limit of simple field kits (approximately 5 mg/L) which rely on melamine precipitation
chemistry (HACH Company, 2014b). Currently, other methods exist that could be used to
measure cyanuric acid concentrations at drinking water relevant concentrations, but they are
complex and include silver nanoparticles (Kappi et al, 2014), high performance liquid
chromatography (Hou & Ding, 2011; Sun et al, 2011; Downes et al, 1984; Briggle et al, 1981),
differential pulse polarography (Struys & Wolfs, 1987), and ultraviolet detection (Downes et al,
4
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1984). Therefore, the TOTCy concentration cannot be measured currently at concentrations
expected in typical drinking water samples in the field.
Simulation A Inputs
^ Note: An initial simulation has not been run; therefore, no plot has been generated
Conditions for Chemical Speciation Plots
pH Range
o 0 CD
Chemical Addition Scenarios
Free Chlorine as chlorine (71 Eq. MW) & Cyanuric Acid as itself (129.07 MW) ~
Added Free Chlorine Concentration (mg Cla/L)
o 10
Simulation B Inputs
^ Note: An initial simulation has not been run; therefore, no plot has been generated
Conditions for Chemical Speciation Plots
pH Range
o so
Chemical Addition Scenarios
Free Chlorine as chlorine (71 Eq. MW) & Cyanuric Acid as itself (129.07 MW) ^
Added Free Chlorine Concentration (mg Cla/L)
o EJjJ
Desired Cyanuric Acid Concentration Input Range
Low Concentration Range (0 to 10 mg/L as itself) ~
Added Cyanuric Acid Concentration (mg/L as itself)
0 Q io
Desired Cyanuric Acid Concentration Input Range
Low Concentration Range (0 to 10 mg/L as itself)
Added Cyanuric Acid Concentration (mg/L as itself)
0
Copy Simulation A's Inputs to Simulation B's Inputs
Copy Simulation B's Inputs to Simulation A's Inputs
Update Simulation A (Press after Finished Changing Simulation Inputs)
Update Simulation B (Press after Finished Changing Simulation Inputs)
Simulation A Chemical Concentration Data Download (csv file)
Simulation B Chemical Concentration Data Download ( csv file)
Figure 3 Simulation input area
As opposed to TOTC1 which will decrease due to the water's chlorine demand and must
be measured directly, TOTCy should be relatively stable in drinking water. Therefore, the
TOTCy concentration may be estimated conservatively by the user from the original dosage of
cyanurate containing chemicals added to the water, requiring the user to know the dosage and
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appropriately calculate the added TOTCy. To serve as a guide, the TOTCy added as cyanuric
acid for each 1 mg/L of the three chemicals approved for use in drinking water and cyanuric acid
is summarized in Table 1, assuming 100% chemical purity.
Table 1 Total cyanurate (TOTCy) addition for each 1 mg/L of chemical addition
Chemical Added as Itself
Molecular Total Cyanuric (TOTCy) Addition as Cyanuric Acid
Weight (mg/L) for each mg/L of Chemical Added as Itself
Cyanuric Acid 129.07
Anhydrous Sodium Dichloroisocyanurate 219.95
Sodium Dichloroisocyanurate Dihydrate 255.98
Trichloroisocyanuric Acid 232.41
1.000
0.587
0.504
0.555
The simulation input area also contains three buttons that allow the user to (1) copy the
current simulation's input conditions directly to the other simulation (Copy Simulation A's Inputs
to Simulation B's Inputs), (2) run the simulation with the provided input conditions and generate
output plots (Update Simulation A and Plots [Press after Finishing Changing Simulation
Inputs]), and (3) export the finished simulation data to a comma-separated variable (.csv) file for
use in external programs {Simulation A Chemical Concentration Data Download [.csv file]).
Plot preferences area. After entering the conditions and running a simulation, the
WBA's next area allows the user to select the Y-axis ranges (Figure 4) for the concentration
plots (Figure 5). For the two log concentration plots (i.e., the top two plots in Figure 5), a range
of 1 to 20 log units is provided. For the mg/L concentration plot (i.e., the bottom plot in Figure
5), the user can select the lower and upper limits on the Y-axis based on a percentage of the
TOTC1. The default is the range of 0-100% which displays the entire TOTC1 range, but the user
can narrow this range to focus in on areas of the mg/L concentration plot as desired to see
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additional detail. Once the user completes the selections, the user may press the Update Plots for
Simulation A (or B) button to immediately update the plots to adjust the Y-axis range displayed.
Simulation A Plot Preferences
Select Range for Y-axis on log Concentration Plots
¦ CD
Simulation B Plot Preferences
Select Range for Y-axis on log Concentration Plots
20 1 Q!) 2o|
Select the Percent of Total Chlorine to use for the Lower and Upper Limits on the mg/L plot Y-axis Select the Percent of Total Chlorine to use for the Lower and Upper Limits on the mg/L plot Y-axis
gg Q53 (S3 KE22
Update Plots for Simulation A Update Plots for Simulation B
Figure 4 Plot preferences area
Output plot area. The WBA generates three plots for each simulation (Figure 5). The
first plot displays a log concentration plot versus pH for all the chemical species simulated. The
second plot produces a plot similar to the first but only includes those species that contain
chlorine and presents the concentrations as the log mg/L as Cb. The third plot focuses in on free
chlorine by displaying TOTC1, free chlorine, hypochlorous acid (HOC1), and hypochlorite ion
(OC1) concentrations as mg/L as CI2.
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Simulation A Chemical Speciation Plots
Simulation B Chemical Speciation Plots
Convergence - Simulation Valid
° -12'
pH
totci2
• TOTFreeCI2
TOTCy
HOCI
ocr
H3cy
H2°y
HCy2"
Cy3-
H2CICy
HCI2Cy
CI3Cy
HCICy"
CICy2"
CI2Cy"
totci2
¦ TOTFreeCI2
HOCI
OCI"
H2CICy
HCI2Cy
CI3Cy
HCICy"
CICy2"
CI2Cy"
10 11
TOTCI2
¦ TOTFreeCI2
HOCI
OCI"
o -a
o
ro "10
o
2 -11
O)
.9 -12
-13
-14
Convergence - Simulation Valid
±35
—"N.
ISt
6
7 8
9
pH
10
1
0
: r:
y
It
'
*
-
s.
•V—
— _
*-
V ^
- "
-3
¦"
¦V.
V
J* v
a"i|^
*
*•
-
-5'
'
V
\
-6
s
-7
\
s
\
.
¦?
\
-
\
10
7
1
1
PH
TOTCI2
• TOTFreeCI2
TOTCy
HOCI
ocr
H3Cy
H2cy"
HCy2"
cy1"
H2CICy
HCI2Cy
CI3Cy
HCICy"
CICy2"
CI2Cy"
TOTCI2
¦ TOTFreeCI2
HOCI
OCI"
H2CICy
HCI2Cy
CI3Cy
HCICy"
cic/"
CI2Cy"
TOTCI2
¦ TOTFreeCI2
HOCI
OCI"
9 10 11
PH
Figure 5 Output plot area
MODEL IMPLEMENTATION
The required chemical reactions and associated equilibrium constants required to simulate the
water chemistry of the free chlorine and cyanuric acid system are presented in Table 2. To
simulate the water chemistry, TOTC1, TOTCy, and pH (which provides the hydrogen ion, H+,
concentration) must be known or assumed (Figure 6). With these three known concentrations,
there are twelve remaining unknown concentrations, which require twelve independent equations
8
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(Eq 1 through Eq 12, Figure 6) to provide a unique solution for the system. Using the twelve
equations (Eqs 1 through 12), a single working equation where only the HOC1 concentration is
unknown can be derived (Eq 15, Figure 7). For each pH, the WBA (i) solves Eq 15 for the
HOC1 concentration, (ii) uses the determined HOC1 concentration to solve Eqs 12 and 13 for the
cyanurate ion (Cy3 ) and OCr concentrations, and (iii) uses the determined Cy3 concentration to
solve Eqs 3 through 11 for the remaining nine unknown chemical concentrations. Please note
that "Cy" represents a shorthand notation of the cyanurate structure which has the chemical
formula of C3N3O3.
Table 2 Required equilibrium reactions and constants to simulate water chemistry
Reaction
Constant
pK a
CbCy ^ HChCy + HOCI
Kla
1.8
HChCy ^ CI2Cy + H+
K2
3.75
hteCICy ^ HCICy + H+
K4
5.33
HsCy ^ H2Cr + H+
Ke
6.88
ChCy ^ HCICy + HOCI
K7a
4.51
HCICy ^ ClCy2" + H+
Ks
10.12
H2Cy- ^ HCy2" + H+
K10
11.40
ClCy2" ^ HCy2" + HOCI
Kl1a
6.90
HCy2" ^ Cy3" + H+
K12
13.5
HOCI ^ OCI" + H+
K
7.54 b
a O'Brien et al (1974) unless otherwise noted
b Morris (1966)
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Assumed Knowns (3)
TOTCl,TOTCy,[H+]
Remaining Unknowns (12)
[CZ3Cy], [HCl2Cy], [H2ClCy], [Cl2Cy~\ [HClCy~], [ClCy2~l [H3Cy\ [H2Cy~\ [,HCy2~], [Cy3"], [HOCl], [OCl~\
Required Equations (12)
TOTCl = 3[CZ3Cy] + 2 [HCl2Cy] + [H2ClCy] + 2 [Cl2Cy~] + [HClCy~] + [CZCy2"] + [HOCl] + [OCT]
TOTCy = [C/3Cy] + [HCl2Cy] + [H2ClCy] + [CZ2Cy"] + [HClCy~] + [C/Cy2"] + [H3Cy] + [H2Cy~] + [HCy2~] + [Cy3"]
[H+][Cy3~
[HCy2~]
\H*][HCy2~
[H2Cy~]
[H*][H2Cy~
W3cy]
lHOCl][HCy2
[ClCy2~]
[H+][ciCy2~]
[HClCy~]
[H+][HClCy~
[H2ClCy]
[HOCl][HClCy~
[iCl2Cy~]
[H+][Cl2Cy-
= K,,
= KU
= K
[ = Ki-
= Kr
= Ka
= k7,
[HCI2 Cy]
= K7
[HOCl][HCl2 Cy]
[Cl3Cy]
[H+][OCl
= Ki,
[H+][H+][Cy3~
[H2Cy~]K12
[H+][fJ+]2 [Cy3~]
K12K10[H3Cy]
lH*]lHOCl][Cy3~
= KU
= K
= K,.
K12[ClCy2
[H*][H*][HOCl]{Cy3~
K12Klla[HClCy~]
[H+][H+]2 [HOCl][Cy3~
K12KllaKslH2ClCy]
= kr
= ka
[HOCl][H*]2[HOCl][Cy3~]
— K7.
K12KllaKs[Cl2Cy-
[H+][H+]2[HOCl]2[Cy3~\ _
K12KllaKsK7a[HCl2Cy]
= K>
[HOCl][H+]3[HOCl]2[Cy3~] _
K12KllaKsK7aK2lCl3Cy] ~ 11
[HCy2~] =
[•H2Cy~] =
[H3Cy] =
[H+][Cy3~]
K12
[fj+]2 [Cy 3—]
^12^10
[H+]3[Cy3~]
Ki2K10K6
[ClCy2~] =
[HClCy~] =
[H2ClCy] =
K12K11 a
[H+]2[HOCl][Cy3~
K12KllaK8
[H+]3[HOCl][Cy3~]
K12KllaK8K4
rr, r,,-1 _ [H+]2[HOCl]2[Cy3-]
ill2Ly j — v v v v
Kl2KliaK8K7a
run r-x, 1 - \H+nnoci\2[cy3-]
ytiLL2Ly\ — K K K
Ki2KnaK8K7aK2
rci Cy 1 = [H+]3[H0C']3[Cy3"]
^ ^I2^na^8^7a^2^ia
[HOCl]
= K
[ocr\ =
K[HOCl]
[H+]
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
Figure 6 System of twelve equations required to solve water chemistry
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Step 1 - Solution of TOTC1 in terms of Cv3 (Eg. 13)
TOTCl = 3[Cl3Cy] + 2 [HCl2Cy] + [H2ClCy] + 2 [Cl2Cy~] + [HClCy] + [ClCy2~] + [HOCl] + [OCl~]
TOT CI = 3 [H"*"]3[H0C']3[cy3~] + 2 [H+]3[H0C']2[Cy3~] _|_ Vt*]3{HOCl][Cy3-} 2 [H+]2[HOg]2[Cy3~] [H*]2[HOCl][Cy3-} [H*][HOCl][Cy3-} VfjQQn + WOCl]
^12^11a^8^7a^2^1a K12KllaK8K7aK2 ^I2^11a^8^4 K12KllaK8K7a K12KllaK8 ^12^11 a l" +
TOTCl = rCv3"l (3 [«+l3[hoc;]3 + 2 Iu+]3[hoci]2 [h+]3[hoci] ^ [h+]2[hoci]2 [h+]2[hoci] [h^[hoo]\ r^ocn + JM
V Ki2^na^8^7a^2^1a ^12^11a^8^7a^2 ^12^11a^8^4 ^12^11a^8^7a ^12^11a^8 K12K11 a ' l"+1'
rorCi-IHOCilfl+rar)
rev i = - (13)
L J [H+]3[HOCq3 [H+]3[HOCq2 [H+]3[HOCq [H+]2[H0CC]2 [H+]2[H0CI] [H+][H0CI] v y
Ki2KiiaK8K7aK2Kia~^ Ki2KnaK8K7aK2 ^ Ki2KnaK8K4~^ Ki2KnaK8K7a ' Ki2KnaK8 ' ^I2^na
Step 2 - Solution of TOTCv in terms of Cv3" (Eg. 14)
TOTCv = [H"*"]3[H0C']3[cy3~] + [H+]3[HOa]2[Cy3~] [H+]3[HOa][Cy3~] [H+]2[HOCl]2[Cy3~] [H+]2[HOCi][Cy3-] [H+][HOCl][Cy3~] [H+]3 [Cy3~] [H+]2 [Cy3~] [ff+][Cy3~] ^ 3_,
^ «l2«lla«B«7a«2Kla K12KllaKaK7,aK2 K12KllaKaKt K12KllaKaK7 a K12KllaKs K12Klla K12KmK6 K12K10 K12
TOTCv = rcv3"l f [H+]3[HO"]3 + [h+]3[hoci]2 [h*]3[hoci] [h*]2[hoci]2 [h*]2[hoci] [h*][hoci] [h+]3 [h+]2 | [h+1 | -A
y L y J \K12KllaKeK7aK2Kla K12KllaKeK7aK2 Kr2K^aKsKt K12KllaKeK7a K12KllaKe K12Klla K12KWK6 K12KW K12 J
rCv3"l = TOTCy -j „
L ^ 1 [//+13 [//0r*.7]'*! |//+|3[//Or-:/]2 [//+13 [//0 C/] [//+12 |//Or",7]2 \H+f [HOCl] \H+][HOCQ ^ |//+|3 |//+|2 [//+ V }
*12*lia*8*7a*2*l£i ' *i2*na*8*7£i*2 ' *i2*na*8*4 ' K12KllaKsK7a ' *12*110*8 ' K12Klla ' *12*10*6 ' *12*10 ' K12 +1
Step 3 - Solution of working eguation (Eg. 15) bv setting Eg. 13 egual to Eg. 14
TOTCl-mcl^l+j^) ^
[H+] [HOCQ3 [H+] [HOCl]2 [H+] [HOCl] [H+] [HOCl]2 [H+] [HOCl] [H+][HOCl] [H+] [HOCQ3 [H+] [HOCQ2 [H+] [HOCQ [H+] [HOCl]2 [H+] [HOCt] [H+][HOCl] [H+] [H+] [H+]
Ki2KnaK8K7aK2Kia+ Ki2KnaK8K7a><2 ' Ki2KnaK8K4 + Ki2KnaK8K7a ' Ki2KnaK8 ' Ki2Kna Ki2KnaK8K7a^2Kia ' Ki2KnaK8K7a><2 ' Ki2KnaK8K4 ' Ki2KnaK8K7a ' Ki2KnaK8 ' Ki2Kna ' ^12^10^6 ' ^12^10 ' K12 *
[H+]S[HOCl]3 ^ [H+]S[HOCl]2 [H+]S[HOCl] ^ [H^f [HOCl]2 [H+]2 [HOCQ [H+][HOCl]
TOTCl [HOCl] ~) = TOTCy Ki2KiiaK8K7aK2Kia Ki2KnaK8K7aK2 K\2KnaK8K4 Ki2KnaK8K7a Ki2KuaK8 k12kha
[H+] [HOCl]3 [H+] [HOCl]2 [H+] [HOCl] [H+] [HOCQ2 [H+] [HOCl] [H+][HOCC] [H+] [H+] [H+]
Ki2KnaK8K7a.K2Kia ' Ki2KnaK8K7al<2 ' Ki2KnaK8K4 ' Ki2KnaK8K7a ' Ki2KnaK8 ' Ki2Kna ' ^12^10^6 ' ^12^10 ' K12 +
^ [H+] [HOCl]3 [H+] [HOCl]2 | [H+] [HOCl] [H+] [HOCl]2 | [H+] [HOC(\ ^[H+^HOCt\
TOTCl = TOTCV Ki2KnaK8K7aK2Kia Ki2KnaK8K7aK2 Ki2KnaK8K4 Ki2KnaK8K7a Ki2KnaK8 Ki2Kna 1 \[{OCl\ (1 4" ^ 1
y fW*"]3 [HOCl]3 \H+]3[HOCC]2 , fW*"]3 [HOCl] , \H+]2[HOCC]2 , \H+]2 [HOCl] , \H+][HOCC] , fH+f , \H+]2 ,\H+] _ ^ \ [H+]J
K12KllaKsK7aK2Kla ' K12KllaKsK7aK2 ' K12KllaKsK4 ' K12KllaKsK7a ' K12KllaKs ' K12Klla ' K12K10K6 ' K12K10 ' K12 +1
^ [H+]S[HOC(I3 [H+]3[HOCf|2 | [H+]3[HOCf| [H+]2[HOCq2 | [H+]2 [HOCt] | [H+][HOCf|
n rnrrv Ki2KnaK8K7aK2Kia Ki2KnaK8K7aK2 Ki2KnaK8K4 Ki2KnaK8K7a Ki2KnaK8 Ki2Kna 1 TW/')/r71 I 1 -I- —^—1 TOTCl (\
y \H+f[HOCl]3 \H+f[HOCq2 \H+f[HOCq \H+]2[HOCl]2 \H+]2[HOCl] \H+][HOCl] \H+f \H+f fH+1 *- [H+]J ^ '
K12KllaKsK7aK2K1a ' K12KllaKsK7aK2 ' *12*110*8*4 ' K12K11aKsK7a ' K12KllaKs ' K12Klla ' K12K10K6 ' K12Km ' 1112 +1
Figure 7 Derivation of working equation (Eq 15) to solve water chemistry
11
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References
APHA, AWWA & WEF, 2005 (21st ed.). Standard Methods for the Examination of Water and
Wastewater. American Public Health Association : American Water Works Association :
Water Environment Federation, Washington, D.C.
Briggle, T.V., Allen, L.M., Duncan, R.C. & Pfaffenberger, C.D., 1981. High Performance Liquid
Chromatographic Determination of Cyanuric Acid in Human Urine and Pool Water.
Journal of the Association of Official Analytical Chemists, 64:5:1222.
Downes, C.J., Mitchell, J.W., Viotto, E.S. & Eggers, N.J., 1984. Determination of Cyanuric Acid
Levels in Swimming Pool Waters by UV Absorbance, HPLC and Melamine Cyanurate
Precipitation. Water Research, 18:3:277.
HACH Company, 2014a. Method 8021, Chlorine, Free. USEPA DPD Method, 0.02 to 2.00
mg/L Ch. Hach Company, Loveland, Colorado.
HACH Company, 2014b. Method 8139, Cyanuric Acid. Turbidimetric Method, 5 to 50 mg/L
(Spectrophotometers), 7 to 55 mg/L (Colorimeters). HACH Company, Loveland,
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