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Supplementary Material
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Transformation of dissolved organic phosphorus to phosphate using UV/H2O2
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Section A. UV Fluence Calculations
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UVCalc 1.0.5 (Bolton Photosciences) can be used to determine the UV fluence rate
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(mW/cm2) for a given annular reactor design and a raw water UV254 absorbance. This fluence
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rate is then multiplied by the UV exposure time to get the UV fluence (mJ/cm2). However,
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UVCalc cannot account for the changes in UV254 absorbance that occur during the course of an
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experiment. As a result, the program underestimates the UV fluence rate because as the
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experiment progresses the UV254 absorbance decreases, leading to a corresponding increase in
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the fluence rate. Due to this limitation, three values for UV fluence are provided for each
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experiment: minimum, maximum, and modeled, shown in Tables A1 and A2. The modeled UV
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fluence values are given in the research article.
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UV254 absorbance data and UVCalc were used to model the actual UV fluence. First, as
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shown in Figure A1 and Equation A1, UVCalc was used to determine an equation for UV
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fluence rate based on the water matrix’s UV254 absorbance.
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𝐹𝑙𝑢𝑒𝑛𝑐𝑒 𝑅𝑎𝑡𝑒 = 2.473(𝐴𝑏𝑠)2 − 7.248(𝐴𝑏𝑠) + 8.260
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(A1)
Where Fluence Rate is the UV fluence rate (mW/cm2) and Abs is UV254 absorbance
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(cm-1). Then, data from this study was used to determine equations for UV254 absorbance based
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on the time of UV exposure and the shown in Figures A3–A4 and Equations A2–A3. The data
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were modeled using an exponential regression because preliminary data from our study, shown
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in Figure A2, and data from other studies clearly show that UV254 reduction is exponential for
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the UV/H2O2 AOP [1,2]. Figure A3 and Equation A2 are for synthetic water experiments,
1
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Figure A4 and Equation A3 are for H2O2 and raw Everglades water, and Figure A5 and Equation
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A4 are for H2O2 and 2× diluted Everglades water.
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𝐴𝑏𝑠 = 0.297𝑒 −0.096𝑡
𝐴𝑏𝑠 = 0.810𝑒 −0.032𝑡
𝐴𝑏𝑠 = 0.503𝑒 −0.052𝑡
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estimated using Equations A1-A4. As an example, substituting Equation A3 into Equation A1
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yields Equation A5.
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𝐹𝑙𝑢𝑒𝑛𝑐𝑒 𝑅𝑎𝑡𝑒 = 2.473 (0.810𝑒 −0.03260 ) − 7.248 (0.810𝑒 −0.03260 ) + 8.260
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Where Fluence Rate is the UV fluence rate (mW/cm2) and t is time (secs). Integrating, Equation
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A5 across time produces UV fluence, as shown Equation A6. Equation A6 shows an example
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calculation for the modeled UV fluence at a UV exposure time of 60 minutes for H2O2.
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𝑈𝑉 𝐹𝑙𝑢𝑒𝑛𝑐𝑒 = ∫0
(A2)
(A3)
(A4)
Where Abs is UV254 absorbance (cm-1) and t is time (min).
𝑡
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3600
21,800
𝑚𝐽
𝑐𝑚2
= 21.8
2
UV fluence can then be
𝑡
𝑡
2
(A5)
𝑡
2.473 (0.810𝑒 −0.03260 ) − 7.248 (0.810𝑒 −0.03260 ) + 8.260 𝑑𝑡 =
𝐽
(A6)
𝑐𝑚2
Where t is time (secs). This procedure was used to calculate all the modeled UV fluences
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shown in Tables A1. One limitation of this approach is the limited data used to develop
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Equations A2-A4. For this reason, we have provided the minimum and maximum possible UV
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fluences for each experiment in Tables A1. The minimum UV fluence is calculated based on the
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fluence rate at the start of the experiment, when the UV254 absorbance of the water matrix is
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highest. In contrast, the maximum UV fluence is calculated based on the fluence rate at the end
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of the experiment, when the UV254 absorbance is lowest. These two values represent the UV
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fluence upper and lower bounds for all experiments.
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Table A1. UV fluence for experiments conducted in this study.
UV Exposure Time (min)
Water Type
Min Dose (J/cm2)
6
10
10-2X
12
12
60
60
60-2X
Syntheticb
Naturald
Naturale
Syntheticb
Syntheticc
Syntheticb
Naturald
Naturale
2.2a
2.0
2.7
4.4a
4.4a
21.9a
12.3
16.2
Max Dose
(J/cm2)
2.7
3.2
4.3
5.6
5.5
29.7
26.6
29.1
Modeled Dose
(J/cm2)
2.4
2.7
3.5
5.1
–f
28.5
21.8
26.1
a
The average initial UV254 value for all synthetic waters was used in this calculation.
H2O2 dose was 50 mg H2O2/L
c
H2O2 dose was 25 mg H2O2/L
d
Raw Everglades water. H2O2 dose was 100 mg H2O2/L
e
2×-diluted Everglades water. H2O2 dose was 100 mg H2O2/L
f
Not enough UV254 data available to synthetic UV fluence. As a result, the modeled fluence for a H 2O2 dose of 50 mg H2O2/L was used as an
estimate.
b
Figure A1. Average UV fluence rates for different UV254 absorbance values for the annular UV
reactor used in this study. Calculated using UVCalc software.
Figure A2. Changes in UV254 absorbance as a function of UV exposure time for raw Everglades
water from STA-1W treated with UV light only.
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Figure A3. Changes in UV254 absorbance as a function of UV exposure time for all synthetic
waters treated with a H2O2 dose of 50 mg H2O2/L.
Figure A4. Changes in UV254 absorbance as a function of UV exposure time for raw Everglades
water from STA-1W treated with a H2O2 dose of 100 mg H2O2/L.
Figure A5. Changes in UV254 absorbance as a function of UV exposure time for 2× diluted
Everglades water from STA-1W treated with a H2O2 dose of 100 mg H2O2/L.
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Section B. Triethly Phosphate (TEP) Molar Absorption coefficient, ε
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TEP ((C2H5)3PO4) from Alfa Aesar was diluted to 1 M in both methanol and DI water [3]. A
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Hitachi U-2900 spectrophotometer was used to determine the absorbance of these solutions
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(subtracting the background solutions) at wavelengths from 200 – 400 nm. Using these
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absorbances and the molar concentration of TEP, the molar absorption coefficient can be
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calculated using the following equation:
ε = A/cl
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(B1)
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Where ε is the molar absorption coefficient (M-1 cm-1), A is absorbance, c is the molar
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concentration of TEP (M), and l is path length (cm). The results for both solutions are shown in
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Figure B1 and Figure B2. The molar absorption coefficient for TEP is less than five at 254 nm
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in both figures. These results show that TEP is a poor light-absorbing compound and does not
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interfere with the creation of hydroxyl radicals during the UV/H2O2 AOP [4].
1.0
ε (M-1 cm-1)
0.8
0.6
0.4
0.2
0.0
200
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250
300
Wavelength (nm)
350
400
Figure B1. Molar absorption coefficients (ε) for TEP in methanol for the wavelength range 200
– 400 nm.
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5
1.0
ε (M-1 cm-1)
0.8
0.6
0.4
0.2
0.0
200
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70
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72
73
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75
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77
78
79
80
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250
300
Wavelength (nm)
350
400
Figure B2. Molar absorption coefficients (ε) for TEP in deionized water for the wavelength
range 200 – 400 nm.
References
1.
Goslan E., Gurses F., Banks J. and Parsons S. (2006). An investigation into reservoir NOM
reduction by UV photolysis and advanced oxidation processes. Chemosphere, 65, 11131119.
2.
Vilhunen S., Vilve M., Vepsäläinen M. and Sillanpää M. (2010). Removal of organic
matter from a variety of water matrices by UV photolysis and UV/H2O2 method, Journal of
Hazardous Materials, 179(1-3), 776-782.
3.
Watts M. (2008). Photochemical degradation of aqueous organics in chlorinated solutions.
PhD Disseration, Duke University, Durham, NC, USA.
4.
Watts M. (2008). Photooxidation and subsequent biodegradability of recalcitrant tri-alkyl
phosphates TCEP and TBP in water. Water Research, 42, 4949-4954
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