ars.els-cdn.com · Web view(Strain: LB 2061, originated from Madison, Wisconsin, USA) was purchased from Culture Collection of Algae at the University of Texas, Austin, TX, USA. Cyanobacterial

Supplementary Material

Formation of iodinated trihalomethanes and noniodinated disinfection byproducts during chloramination of algal organic matter extracted from Microcystis aeruginosa

Chao Liu1, Mahmut S. Ersan1, Michael J. Plewa2, Gary Amy1, and Tanju Karanfil1*

1. Department of Environmental Engineering and Earth Sciences, Clemson University,

Anderson, South Carolina 29625, United States

2. Department of Crop Sciences, and the Safe Global Water Institute, University of Illinois

at Urbana-Champaign, Urbana, Illinois 61801, United States

*Corresponding author: email: [email protected]

30 Pages

5 Text Sections

3 Tables

18 Figures

1 Scheme

S1

Text S1. Standards and description of reagents.

A sodium hypochlorite (NaOCl) solution was used as the source of chlorine (5% active chlorine,

J.T.Baker). EPA 501/601 trihalomethanes calibration mix (2000 µg/mL each component in

methanol), including chloroform, dichlorobromomethane, dibromochloromethane and

bromoform was provide by Supelco (Sigma-Aldrich). EPA 551B halogenated volatiles mix

(2000 µg/mL each component in acetone), including bromochloroacetonitrile (BCAN),

dibromoacetonitrile (DBAN), dichloroacetonitrile (DCAN), trichloroacetonitrile (TCAN) was

provide by Supelco (Sigma-Aldrich). Dichloroiodomethane (DCIM), bromochloroiodomethane

(BCIM), dibromoiodomethane (DBIM), chlorodiiodomethane (CDIM), bromodiiodomethane

(BDIM), bromodichloroacetaldehyde (BDCAL), dibromochloroacetaldehyde (DBCAL), and

tribromoacetaldehyde (TBAL) were purchased from CanSyn Chem. Corp. Triiodomethane

(TIM), chloroacetonitrile (CAN), and bromoacetonitrile (BAN) were provided by Sigma-

Aldrich.

Text S2. Culturing of cyanobacteria and extraction of algal organic matter (AOM)

Microcystis aeruginosa (Strain: LB 2061, originated from Madison, Wisconsin, USA) was

purchased from Culture Collection of Algae at the University of Texas, Austin, TX, USA.

Cyanobacterial cells were cultured in 5 L of BG-11 media with fluorescent lamps under

automatic dark and light cycles (12 h dark and 12 h light daily) at room temperature (21±1 C).

The number of cells in the suspension was measured with a microscope (Axioskop 2 plus, Zeiss,

Germany) (Liu et al. 2018).

The extraction of AOM was conducted according to our previous study (Liu et al. 2018).

Cyanobacterial cells were collected during the late exponential growth phase. A centrifuge

process with a rate of 5000 rpm for 15 min was used to separate the cells from the media. After

discarding the supernatant, remaining cells were rinsed with MQ water for at least three times to

remove the constituents from the media. Three freeze−thaw cycling (−77 °C in a freezer and 35

°C in water bath) was employed to break the cells. Afterwards, cells were sonicated for 30 min in

an ice bath to release the AOM. The centrifuge process was used again to separate the

suspensions containing cell debris and AOM, and then supernatant was filtered with 0.45 μm

cellulose acetate membranes. The filtrate was used as AOM.

S2

Text S3. Analytical methods

Ultraviolet (UV) absorbance at 254 nm was measured using a Cary 50 UV-Vis

spectrophotometer (Varian) based on Standard Method 5910B (American Public Health

Association 1998). Samples were placed in a 1 cm quartz cuvette and measured at a wavelength

of 254 nm.

The total dissolved organic carbon (DOC) and dissolved nitrogen (DN) were determined with a

Shimadzu TOC-VCHS or TOC-LCHS high temperature combustion analyzer (Shimadzu Corp.,

Kyoto, Japan) equipped with a TN module according to Standard Method 5310B (American

Public Health Association 1998). TOC standards were prepared by diluting 1000 mg C/L

potassium hydrogen phthalate solution in the range of 0.2-15 mg C/L. TN standards were

prepared by diluting 1000 mg N/L potassium nitrate solution in the range of 0.2-5 mg N/L. The

MRLs for these measurements were determined to be 0.15 mg/L and 0.1 mg/L for DOC and DN,

respectively.

Concentrations of hypohalous acid (HOX, the sum of HOCl, HOBr and HOI) were analyzed

spectrophotometrically by the N,N-diethyl-p-phenylenediamine (DPD) method at 515 nm on a

UV-visible spectrophotometer (Cary 50) (American Public Health Association 1998).

A Dionex ICS-2100 ion chromatography system (Dionex, Sunnyvale, CA) was used to

determine nitrite, nitrate, chloride, bromide and iodide concentrations in aqueous solutions. The

mobile phase for the system was 20 mM KOH and a dionex AS-19 column coupled with an AG-

19 guard column were used for separation. The minimum reporting limit for nitrite, nitrate,

chloride, bromide, and iodide was 20, 15, 5, 10, and 25 μg/L, respectively.

Iodate was quantified by a Dionex 2100 reagent free ion chromatograph (IC) through AS 19

analytical column with a post-column reaction unit with UV/Vis detection of I3- at 351 nm

according to a previous method with some modifications (Salhi and von Gunten 1999). The

quantification limit of IO3−was 0.5 μg/L and the standard deviation was <10%.

S3

For the analyses of trihalomethanes (THMs), haloacetonitriles (HANs), iodinated

trihalomethanes (I-THMs), and haloacetaldehydes (HALs), samples (40 mL) were transferred

into 60 ml extraction vials which was followed by addition of 2.4 ml of MtBE and 10 g of pre-

oven dried sodium sulfate, respectively. The extraction vials were then placed on a shaker table

for 30 min. After 30 min, vials were placed on the bench for 10 min for phase separation. MtBE

phase was withdrawn and analyzed on an Agilent 6890 GC equipped with a DB-1 column (J&W

Scientific 30m x 0.25mm x 0.001mm), and an electron capture detector (ECD). The GC

temperature program was 35 C for 15 min, 25 C/min to 145 C and hold for 3 min, 35 C/min to

240 C and hold for 5 min. A 2 mL injection volume was used in splitless mode. The carrier and

make-up gases were ultra-high purity (UHP) hydrogen and UHP nitrogen, respectively. The total

run time was 30.11 min. The injector and detector temperatures were set at 230 and 260 C,

respectively. The minimum reporting limit for DBP measurements was 0.2 µg/L.

Text S4. Calculations of iodine substitution factor and iodine utilization factor.

Iodine substitution factor (ISF, between 0 and 1) is defined as the ratio of the molar

concentration of iodine incorporated into a given class of DBPs to the total molar concentrations

of chlorine, bromine and iodine in that class, as shown in Equation 1.

DBP

DBP DBP DBP

IISF=

Cl Br I

1

When THM (10 species, including six I-THMs and THM4) was used as an example, molar

concentrations of iodine and sum of chlorine, bromine and iodine could be calculated by

Equations 2 and 3, respectively, where THM10 is sum of 10 species of THMs. ISF of THM can

be calculated by Equation 4.

THMI = [DCIM] + [BCIM]+ [DBIM]+ 2[CDIM]+ 2[BDIM]+ 3[TIM] 2

THMTHM THMCl Br I 3[THM10] 3

THM

THM

IISF =

3[THM10]

4

Iodine utilization factor (IUF, between 0 and 1) is defined as the ratio of the molar

concentration of iodine incorporated into the quantified DBPs to the initial molar concentrations

of iodine, as shown in Equation 5.

S4

DBP

-0

IIUF=

[I ]

4

Text S5. Calculations of theoretical cytotoxicity. The theoretical cytotoxicity assessment was

performed by dividing measured molar concentrations of each group of DBPs by concentrations

(i.e., LC 50 value) determined in toxicological assays and assuming that toxicity is additive

(Yeatts et al. 2010). This approach has been used to assess toxicity of measured DBPs and

evaluate the contribution of individual DBPs to the total DBP-associated toxicity (Krasner et al.

2016, Smith et al. 2010). The LC50 value is the concentration of each individual DBP inducing a

50% reduction in the density of Chinese Hamster Ovary cells for 72h (Wagner and Plewa 2017).

The LC 50 values of individual DBPs (THM4, I-THMs, HANs, and HALs) were available in

literature (Wagner and Plewa 2017), which are also presented in the Tables S2.

S5

Table S1. Characteristics of DOM solutions in this study

Name Abbreviation DOC (mg/L)

DON(mg/L)

DOC/DON UV254

SUVA(L/mg m)

Br−

(g/L)I−

(g/L)

Hydrophobic NOM isolate extracted from raw water at water treatment plant in South Carolina, U.S.

RW 2.0 0.1 20 0.0816 4.0 0 0

Hydrophobic NOM isolate extracted from treated water after sedimentation at water treatment plant in South Carolina, U.S.

TW 2.2 0.1 22 0.0569 2.5 0 0

Blending waters containing 50% AOM*

50%TW+50%AOM 1.0 - - - 2.0 0 0

Blending waters containing 75% AOM*

25%TW+75%AOM 1.0 - - - 1.7 0 0

AOM extracted from Microcystis aeruginosa

AOM 1.96 0.35 5.5 0.029 1.5 0 0

* Before the blending, the DOC of AOM and TW NOM solutions were adjusted to 1 mg/L.

S6

Table S2. Chinese hamster ovary cell cytotoxicity of target halogenated DBPs in literature

DBPs LC50 (M) References

THMsTCM 9.62×10−3 (Plewa and Wagner 2009)BDCM 1.15×10−2 (Plewa and Wagner 2009)DBCM 5.35×10−3 (Plewa and Wagner 2009)TBM 3.96×10−3 (Plewa and Wagner 2009)I-THMsDCIM 4.13×10−3 (Richardson et al. 2008)BCIM 2.42×10−3 (Richardson et al. 2008)DBIM 1.91×10−3 (Richardson et al. 2008)CDIM 2.41×10−3 (Richardson et al. 2008)BDIM 1.4×10−3 (Richardson et al. 2008)TIM 6.60×10−5 (Richardson et al. 2008)HANsCAN 6.83×10−5 (Muellner et al. 2007)BAN 3.21×10−6 (Muellner et al. 2007)DCAN 5.73×10−5 (Muellner et al. 2007)BCAN 8.46×10−6 (Muellner et al. 2007)DBAN 2.85×10−6 (Muellner et al. 2007)TCAN 1.60×10−4 (Muellner et al. 2007)HALsTCAL 1.16×10−3 (Jeong et al. 2015)BDCAL 2.04×10−5 (Jeong et al. 2015)DBCAL 5.15×10−6 (Jeong et al. 2015)TBAL 3.58×10−6 (Jeong et al. 2015)

S7

Table S3: Rate constants for the reactions of Br- and I- with oxidants in Cl2-NH2Cl processNo. Reactions Rate constants

(M-1 s-1)

pKa References

1 HOCl==> OCl- + H+ 7.6 (Morris 1966)

2 H+ + OCl- ==> HOCl

3 HOBr==> OBr- + H+ 8.8 (Haag and Hoigné 1983)

4 OBr- + H+ ==> HOBr

5 HOI==> OI- + H+ 10.4 (Bichsel and von Gunten 2000)

6 H+ + OI- ==> HOI

7 HOCl +I- ==> HOI + Cl- 4.30×108 (Nagy et al. 1988)

8 HOCl + Br- ==> HOBr +Cl- 1.55×103 (Kumar and Margerum 1987)

9 OCl- + Br- ==> OBr- +Cl- 9.00×10-4 (Kumar and Margerum 1987)

10 HOBr +I- ==> HOI + Br- 5.00×109 (Troy and Margerum 1991)

11 OBr- +I- ==> OI- + Br- 6.80×105 (Troy and Margerum 1991)

12 HOCl + HOI==> IO2- + Cl- + 2H+ 8.2 (Bichsel and von Gunten 1999)

13 OCl- + HOI ==> IO2- + Cl- + H+ 52 (Bichsel and von Gunten 1999)

14 HOBr + OI-==> IO2- + Br- + H+ 1.90×106 (Criquet et al. 2012)

15 OBr- + OI- ==> IO2- + Br- 1.80×103 (Criquet et al. 2012)

16 HOCl + IO2- ==> IO3

- + Cl- + H+ 1.00×106 (Liu et al. 2014)

17 OCl- + IO2- ==> IO3

- + Cl- 1.00×106 (Liu et al. 2014)

18 HOBr + IO2- ==> IO3

- + Br- + H+ 1.00×108 (Liu et al. 2014)

19 OBr- + IO2- ==> IO3

- + Br- 1.00×108 (Liu et al. 2014)

20 NH2Cl + I- + H3O+==> HOI + Cl- +NH3 2.40×1010 M-2 s-1 (Kumar et al. 1986)

21 HOCl/OCl- +NH3/NH4+ ==> NH2Cl +

H+/H2O/OH-8.1×103 (pH = 7) (Heeb et al. 2017)

22 NH2Cl + H2O ==> HOCl +NH3 2.1×10-5 s-1 (Morris and Isaac 1981 )

23 HOBr/OBr- +NH3/NH4+ ==> NH2Br +

H+/H2O/OH-3.1×105 (pH = 7) (Heeb et al. 2017)

24 NH2Br + H2O ==> HOBr + NH3 1.5×10-3 s-1 (Heeb et al. 2014)

25 2NH2Cl + Br- + H+ ==> NHClBr + Cl- + NH4+ (3.8×105-1.4×106)

M-2 s-1

(Luh and Mariñas 2014, Trofe et al.

1980)

S8

Figure S1. Effect of DOM type on the HOX concentrations at different reaction time. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 = 28 M (2 mg/L as Cl2) (2.2 and 2.5 mg as Cl2 for 25%TW +75%AOM and AOM, respectively), [I−]0 = 0.5 M, [Br−]0 = 5.0 M, pH= 8.0, T =21±1 C.

0 2 5 10 15 30 24h0

10

20

30

40

RW TW 50% TW + 50% AOM 25% TW + 75% AOM AOM

Reaction time (min)

HO

X (

M)

S9

Figure S2. Effect of DOM type on the formation of iodate. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 or [NH2Cl]0 = 28 M (2 mg/L as Cl2) (2.2 and 2.5 mg/L as Cl2 for 25%TW +75%AOM and AOM, respectively), [I−]0 = 0.5 M, [Br−]0 = 5.0 M, pH= 8.0, T =21±1 C, reaction time = 24 h. For NH2Cl process, preformed NH2Cl was used. For Cl2-NH2Cl process, after 2 -30 min chlorination, reaction solutions were quenched with NH4Cl (5 times of [HOCl]0).

2 5 15 300.0

0.1

0.2

0.3

0.4

0.5

0.6


Ioda

te (

M)

Initial iodide concentration

Cl2

NH2Cl Cl2 time in Cl2-NH2Cl (min)

S10

Figure S3. Effect of DOM type on the formation of (a) HANs and (b) HALs. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 or [NH2Cl]0 = 28 M (2 mg/L as Cl2) (2.2 and 2.5 mg/L as Cl2 for 25%TW +75%AOM and AOM, respectively), [I−]0 = 0.5 M, [Br−]0 = 5.0 M, pH= 8.0, T =21±1 C, reaction time = 24 h. For NH2Cl process, preformed NH2Cl was used. For Cl2-NH2Cl process, after 2 -30 min chlorination, reaction solutions were quenched with NH4Cl (5 times of [HOCl]0).

S11

0

10

20

30

40

50(a)

TCAN DBAN BCAN DCAN BAN CAN

25% TW + 75%AOM

AOM

50% TW + 50% AOM

TW

DB

Ps (n

M)

RW

2 5 15 300

2

4

6

8 TBAL DBCAL BDCAL TCAL

25%TW + 75% AOM

AOM

50% TW + 50% AOM

TW

DB

Ps (n

M)

RW

(b)

Cl2NH

2Cl Cl2 time in Cl2-NH2Cl (min)

Figure S4. Effect of DOM type on the IUF. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 or [NH2Cl]0 = 28 M (2 mg/L as Cl2) (2.2 and 2.5 mg/L as Cl2 for 25%TW +75%AOM and AOM, respectively), [I−]0 = 0.5 M, [Br−]0 = 5.0 M, pH= 8.0, T =21±1 C, reaction time = 24 h. For NH2Cl process, preformed NH2Cl was used. For Cl2-NH2Cl process, after 2 -30 min chlorination, reaction solutions were quenched with NH4Cl (5 times of [HOCl]0).

2 5 15 300.0

0.2

0.4

0.6

0.8

1.0

RW TW 50% TW + 50% AOM 25% TW + 75% AOM AOMIU

F

Cl2


S12

Figure S5. Effect of DOM type on the plot of iodate formation vs chlorine exposure. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 or [NH2Cl]0 = 28 M (2 mg/L as Cl2) (2.2 and 2.5 mg/L as Cl2 for 25%TW +75%AOM and AOM, respectively), [I−]0 = 0.5 M, [Br−]0

= 5.0 M, pH= 8.0, T =21±1 C, reaction time = 24 h.

0 10 20 30 40 500.0

0.1

0.2

0.3

0.4

0.5

0.6



Ioda

te (

M)

Chlorine exposure (min mg/L)

S13

Figure S6 Calculated reduction potentials for chlorine, bromine and iodine (pH: 6.6-9.6).

6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.00.4

0.6

0.8

1.0

1.2

1.4

EHOCl/Cl-

EHOBr/Br-E

(V)

pH

EHOI/I-

S14

Figure S7. Effect of DOM concentration on HOX concentrations at different reaction time. Experimental conditions: [DOC] = 0.5, 1.0, 2.0, and 4.0 mg C/L (corresponding [HOCl]0 = 1.3, 2.0, 3.5, and 7.0 mg/L as Cl2, respectively), [I−]0 = 0.5 M, [Br−]0 = 2.5 M, pH= 7.5, T =21±1 C.

0 2 5 15 30 24h0

20

40

60

80

100

120

0.5 mgC/L 1.0 mgC/L 2.0 mgC/L 4.0 mgC/L

Reaction time (min)

HO

X (

M)

S15

Figure S8. Effect of DOM concentration on the formation of iodate. Experimental conditions: [DOC] = 0.5, 1.0, 2.0, and 4.0 mg C/L (corresponding [HOCl]0 or [NH2Cl]0 = 1.3, 2.0, 3.5, and 7.0 mg/L as Cl2, respectively), [I−]0 = 0.5 M, [Br−]0 = 2.5 M, pH= 7.5, T =21±1 C, reaction time = 24 h. For NH2Cl process, preformed NH2Cl was used. For Cl2-NH2Cl process, after 2- 30 min chlorination, reaction solutions were quenched with NH4Cl (5 times of [HOCl]0).

2 5 15 300.0

0.1

0.2

0.3

0.4

0.5

0.6


Ioda

te (

M)


Cl2NH

2Cl Cl2 time in Cl2-NH2Cl (min)

S16

Figure S9. Effect of DOM concentration on the plot of iodate formation vs chlorine exposure. Experimental conditions: [DOC] = 0.5, 1.0, 2.0, and 4.0 mg C/L (corresponding [HOCl]0 or [NH2Cl]0 = 1.3, 2.0, 3.5, and 7.0 mg/L as Cl2, respectively), [I−]0 = 0.5 M, [Br−]0 = 2.5 M, pH= 7.5, T =21±1 C, reaction time = 24 h.

0 20 40 60 80 100 1200.0

0.1

0.2

0.3

0.4

0.5

0.6Initial iodide concentration


Ioda

te (

M)


S17

Figure S10. Effect of initial bromide concentration on HOX concentrations at different reaction time. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 or [NH2Cl]0 = 28 M (2 mg/L as Cl2) (2.2 mg/L for [Br−]0 = 5.0 M), [I−]0 = 0.5 M, [Br−]0 = 0-5.0 M, pH= 7.5, T =21±1 C.

0 2 5 15 30 24h0

10

20

30

40

0.0 M [Br-]0

0.5 M [Br-]0

2.5 M [Br-]0

5.0 M [Br-]0

Reaction time (min)

HO

X (

M)

S18

Figure S11. Effect of initial bromide concentration on iodate formation. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 or [NH2Cl]0 = 28 M (2 mg/L as Cl2) (2.2 mg/L for [Br−]0 = 5.0 M), [I−]0 = 0.5 M, [Br−]0 = 0-5.0 M, pH= 7.5, T =21±1 C, reaction time = 24 h. For NH2Cl process, preformed NH2Cl was used. For Cl2-NH2Cl process, after 2-30 min chlorination, reaction solutions were quenched with NH4Cl (5 times of [HOCl]0).

2 5 15 300.0

0.1

0.2

0.3

0.4

0.5

0.6

0.0 M [Br-]0

0.5 M [Br-]0

2.5 M [Br-]0

5.0 M [Br-]0

Ioda

te (

M)


Cl2NH2Cl Cl2 time in Cl2-NH2Cl (min)

S19

Figure S12. Effect of initial bromide concentration on the plot of iodate formation vs chlorine exposure. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 = 28 M (2 mg/L as Cl2) (2.2 mg/L for [Br−]0 = 5.0 M), [I−]0 = 0.5 M, [Br−]0 = 0-5.0 M, pH= 7.5, T =21±1 C.

0 10 20 30 400.0

0.1

0.2

0.3

0.4

0.5

0.6


0.0 M [Br-]0

0.5 M [Br-]0

2.5 M [Br-]0

5.0 M [Br-]0

Ioda

te (

M)


S20

Figure S13. Effect of pH on HOX concentrations at different reaction time. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 = 28 M (2 mg/L Cl2), [I−]0 = 0.5 M, [Br−]0 = 2.5 M, pH= 6.0-9.0, T =21±1 C.

0 2 5 15 30 24h0

10

20

30

40

pH 6.0 pH 7.5 pH 9.0

Reaction time (min)

HO

X (

M)

S21

Figure S14. Effect of pH on the iodate formation. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 = 28 M (2 mg/L Cl2), [I−]0 = 0.5 M, [Br−]0 = 2.5 M, pH= 6.0-9.0, T =21±1 C. For NH2Cl process, preformed NH2Cl was used. For Cl2-NH2Cl process, after 2-30 min chlorination, reaction solutions were quenched with NH4Cl (5 times of [HOCl]0).

2 5 15 300.0

0.1

0.2

0.3

0.4

0.5

0.6

pH 6.0 pH 7.5 pH 9.0

Ioda

te (

M)



S22

Figure S15. Effect of pH on the formation of (a) HANs, and (b) HALs. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 or [NH2Cl]0 = 28 M (2 mg/L as Cl2), [I−]0 = 0.5 M, [Br−]0 = 2.5 M, pH= 6.0-9.0, T =21±1 C, reaction time = 24 h. For NH2Cl process, preformed NH2Cl was used. For Cl2-NH2Cl process, after 2-30 min chlorination, reaction solutions were quenched with NH4Cl (5 times of [HOCl]0).

S23

2 5 15 300

5

10

15

20

25

30

TBAL DBCAL BDCAL TCAL

pH 7.5pH 9.0

DB

Ps (n

M)

pH 6.0

(b)

Cl2NH

2Cl Cl

2 time in Cl

2-NH

2Cl (min)

0

10

20

30

40(a)


pH 7.5pH 9.0

DB

Ps (n

M)

pH 6.0

Figure S16. Effect of pH on the (a) IUF and (b) ISF. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 or [NH2Cl]0 = 28 M (2 mg/L as Cl2), [I−]0 = 0.5 M, [Br−]0 = 2.5 M, pH= 6.0-9.0, T =21±1 C, reaction time = 24 h. For NH2Cl process, preformed NH2Cl was used. For Cl2-NH2Cl process, after 2-30 min chlorination, reaction solutions were quenched with NH4Cl (5 times of [HOCl]0).

S24

0.0

0.2

0.4

0.6

0.8

1.0

pH 6.0 pH 7.5 pH 9.0

IUF

(a)

2 5 15 300.0

0.2

0.4

0.6

0.8

1.0 pH 6.0 pH 7.5 pH 9.0

ISF

(b)


Figure S17. Effect of the Cl2/N ratio on the formation of (a) THM4, (b) HANs, and (c) HALs. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 or [NH2Cl]0 = 28 M (2.0 mg/L as Cl2), [I−]0 = 0.5 M, [Br−]0 = 2.5 M, pH= 7.5, T =21±1 C. For NH2Cl process, preformed NH2Cl (molar ratios of Cl2 to NH4Cl = 1.0, 0.7, and 0.2) was used. For Cl2-NH2Cl process, after 2-30 min chlorination, reaction solutions were quenched with NH4Cl (molar ratios of Cl2 to NH4Cl = 1.0, 0.7, and 0.2).

S25

0

10

20

30

[Cl2]:[N]= 1.0 [Cl2]:[N]= 0.2

[Cl2]:[N]= 0.7


DB

Ps (n

M)

(b)0

10

20

30

40

50

60

[Cl2]:[N]= 0.2

[Cl2]:[N]= 0.7

[Cl2]:[N]= 1.0

TBM DBCM BDCM TCM

DB

Ps (n

M)

(a)

2 5 15 300

5

10

15

[Cl2]:[N]= 0.2

[Cl2]:[N]= 0.7

[Cl2]:[N]= 1.0

TBAL DBCAL BDCAL TCAL

DB

Ps (n

M)

(c)

Cl2


Figure S18. Effect of the Cl2/N ratio on the (a) IUF and (b) ISF. Experimental conditions: [DOC] = 1.0 mg C/L, [HOCl]0 or [NH2Cl]0 = 28 M (2.0 mg/L as Cl2), [I−]0 = 0.5 M, [Br−]0 = 2.5 M, pH= 7.5, T =21±1 C. For NH2Cl process, preformed NH2Cl was used. For Cl2-NH2Cl process, after 2-30 min chlorination, reaction solutions were quenched with NH4Cl (molar ratios of Cl2 to NH4Cl = 1.0, 0.7, and 0.2).

S26

2 5 15 300.0

0.2

0.4

0.6

0.8

1.0 [Cl2]:[N]= 1.0 [Cl2]:[N]= 0.7 [Cl2]:[N]= 0.2

ISF

(b)


0.0

0.2

0.4

0.6

0.8

1.0

[Cl2]:[N]= 1.0 [Cl2]:[N]= 0.7 [Cl2]:[N]= 0.2

IUF

(a)

Scheme S1. Potential reactions for the formation of I-DBPs during Cl2-NH2Cl processes.

Br- HOBr/OBr-

HOCl/OCl- NH2Cl

HOCl Cl-

Cl-DOM

Cl-

IO3-

I-DOM

I-

DOM

DOMox

NH3

X HOI/OI-

DOMox

DOM

HOCl Cl-

NH3

NH2BrNH3

Br-DOMDOMox

DOM

HOCHOBr

Cl-/Br-

I-

I-

HOI/OI- I-DOMI-DBPs (e.g., CHI3)

Br-DOM

I/Cl-DBPs (e.g., CHClI2)Cl-DOM

I/Br-DBPs (e.g., CHBrI2)

NH3 addition ChloraminationChlorination

S27

References

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