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Evaluation and improvement of total organic bromineanalysis with respect to reductive property of activated carbon

Yao Li a, Xiangru Zhang a,*, Chii Shang a, Stuart W. Krasner b

aDepartment of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon,

Hong Kong SAR, ChinabMetropolitan Water District of Southern California, 700 Moreno Ave., La Verne, CA 91750, USA

a r t i c l e i n f o

Article history:

Received 4 July 2010

Received in revised form

22 September 2010

Accepted 28 September 2010

Available online 7 October 2010

Keywords:

Disinfection byproducts

Total organic halogen

Total organic bromine

Drinking water

Activated carbon

* Corresponding author. Tel.: þ86 852 2358 8E-mail address: xiangru@ust.hk (X. Zhan

0043-1354/$ e see front matter ª 2010 Elsevdoi:10.1016/j.watres.2010.09.038

a b s t r a c t

A collective parameter and a toxicity indicator for all the halogenated organic disinfection

byproducts in a water sample is total organic halogen (TOX), which can be differentiated as

total organic chlorine (TOCl), total organic bromine (TOBr) and total organic iodine. The

TOX method involves concentration of organic halogens from water by adsorption onto

activated carbon (AC). A previous study showed that a portion of TOCl can be reduced to

chloride during the adsorption procedure, which can be minimized by ozonation of the AC.

In this study, a portion of TOBr was sometimes found to be reduced by AC to bromide, and

the reduction was generally less than that of corresponding TOCl. The results suggested

that around 10% of brominated Suwannee River fulvic acid was reduced to bromide.

However, some brominated amino compounds (especially glycylglycine, phenylalanine,

and cytosine) were found to be more reactive with the AC. For the iodinated compounds

studied, the reduction to iodide was not significant. The method for the TOBr measurement

was improved by using ozonated AC when reduction occurred on the original AC. The

improved method was also evaluated on treated wastewater and swimming pool water

samples.

ª 2010 Elsevier Ltd. All rights reserved.

1. Introduction brominated DBPs generally are dozens to hundreds times

When bromide is present in water (e.g., due to saltwater

intrusion, connate water, oil field brines), hypobromous acid

will be rapidly formed with the addition of chlorine or other

disinfectants. Hypobromous acid undergoes reactions with

organic matter in the water to form organic disinfection

byproducts (DBPs) that contain bromine (Cowman and Singer,

1996; Richardson, 1998; Richardson et al., 2003; Xie, 2004).

Kinetic studies have shown that the reaction of organicmatter

with hypobromous acid is much faster than that with hypo-

chlorous acid (Westerhoff et al., 2003; Acero et al., 2005; Echigo

and Minear, 2006; Hua et al., 2006). Research has shown that

479; fax: þ86 852 2358 153g).ier Ltd. All rights reserved

more toxic than their chlorinated analogues (Plewa and

Wagner, 2009). For instances, bacterial studies have shown

that bromoacetic acid is 201.3 times more mutagenic in

Salmonella typhimurium strain TA100 than chloroacetic acid;

mammalian cell studies have shown that bromoacetic acid is

89.8 timesmore cytotoxic in Chinese hamster ovary cells than

chloroacetic acid; bromoacetic acid is 23.6 times more geno-

toxic in Chinese hamster ovary cells than chloroacetic acid

(Plewa et al., 2004). With the presence of iodide in water,

iodinated DBPs can also be formed during disinfection (Bichsel

and von Gunten, 1999). Iodinated DBPs might be several times

more toxic than their brominated analogues (Plewa et al.,

4.

.

wat e r r e s e a r c h 4 5 ( 2 0 1 1 ) 1 2 2 9e1 2 3 71230

2004), but they are typically formed at lower concentrations

(Krasner et al., 2006).

Even though brominated (and iodinated) DBP species are

being increasingly discovered, numerous of them remain

unknown (Krasner et al., 2006; Ding and Zhang, 2009). A

collective parameter to give an estimation of all forms of

organic-bound halogenated DBPs (Jekel and Roberts, 1980) is

total organic halogen (TOX). As “a master parameter” and “a

toxicity indicator” for halogenated organic DBPs, TOX has

been studied and applied in more than 800 journal papers

(Singer and Chang, 1989; Li et al., 2002, 2010 and references

therein). An improvement in TOX measurement will surely

benefit researchers and practitioners in the more accurate

study/control of halogenated organic DBPs in drinking waters,

wastewaters, swimming pool waters, etc. The components of

TOX include total organic chlorine (TOCl), total organic

bromine (TOBr) and total organic iodine (TOI). TOX, TOCl,

TOBr, and TOI can bemeasuredwith the adsorptionepyrolysis

method based on Standard Method 5320B (APHA et al., 1995;

Hua and Reckhow, 2006). The first two steps of this method

involve enrichment of organic halogens from water by

adsorption onto activated carbon (AC), and elimination of

inorganic halides present on the AC by competitive displace-

ment by nitrate ions.

Because AC can also act as a reductant, if some haloge-

nated DBPs are reduced to inorganic halides when in contact

with AC, they will be removed from the AC during the rinse

step with nitrate, leading to an underestimation of the

amount of TOX present. In a previous study, a portion of TOCl

has been found to be reduced during the adsorption proce-

dure, where w20% of chlorinated Suwannee River fulvic acid

(SRFA) was reduced to chloride by AC (Li et al., 2010). For the

same concentrations, brominated (and iodinated) DBPs are

thought to have significantly higher adverse health effects

than their chlorinated analogues (Plewa andWagner, 2009), so

there is a critical need to evaluate and improve the accuracy of

the TOBr (and TOI) measurement. In the current research, the

reduction of TOBr by AC during the TOX measurement was

evaluated, and the extent to which this reduction affects the

measurement of TOBr was explored with various types of

organics. Also, according to the previous study, AC that was

slightly oxidized by ozone can fully or partially inhibit the

reductive property of the AC. Thus, whether ozonated AC can

also inhibit the reduction of TOBr but still maintain its

adsorption capacity was investigated. In addition, the reduc-

tions of some iodine- and chlorine-containing DBPs (i.e., TOI

and TOCl) by AC were evaluated and compared following

a similar procedure.

2. Materials and methods

2.1. Preparation of halogenated samples

All solutions used in this study were prepared with ultrapure

water (18.2 MU/cm) supplied by a NANOpure system (Barn-

stead). A chlorine stock solution (5000e5500 mg/L as Cl2) was

prepared by absorption of ultra high-purity chlorine gas with

a 1.0 M NaOH solution. By following the method outlined by

Pinkernell et al. (2000), a bromine stock solution (13 mg/L as

Br2) was prepared from a 0.20 mM solution of potassium

bromide by addition of 0.25 mM of an ozone solution at pH 4

(10 mM phosphate buffer). The bromine solution was stan-

dardized by Standard Method 4500F (APHA et al., 1995). After

the pH was adjusted to 11 by sodium hydroxide, the bromine

solution was stable for several days when stored at 4 �C. Thepreparation of an iodine stock solution followed a similar

procedure. The bromine and iodine stock solutions were

adjusted to pH 6.5 before use. Compared to the commercial

ones, the bromine and iodine stock solutions generated in

such a method minimized the levels of inorganic halides in

them by over 50%. SRFA from the International Humic

Substances Society was dissolved into ultrapure water to

prepare a SRFA stock solution.

One brominated SRFA sample was prepared. The initial

concentrations of SRFA and bromine were 3 mg/L as C and

2 mg/L as Br2, respectively. Bromide is naturally present in

many sourcewaters across theworld, with the highest natural

level of w2 mg/L present in Israel’s source water (Richardson

et al., 2003). The high concentration of bromine (from oxida-

tion of bromide during chlorination) was used to magnify the

possible reactions and products. The pH of the sample was

w6.8. After a reaction time of 5 d at ambient temperature

(20 �C), the sample was measured for bromine residual with

the DPD ferrous titrimetric method (APHA et al., 1995). After

5 d, no residual bromine was left in the brominated SRFA

sample.

In addition, one chlorinated SRFA sample with/without

ultrafiltration was prepared based on a previous study (Li

et al., 2010). The initial concentrations of SRFA and chlorine

were 3 mg/L as C and 5 mg/L as Cl2, respectively, which were

used to simulate the typical concentrations in drinking water

treatment. The reaction lasted for 5 d at ambient temperature.

After 5 d, no residual chlorine was left in the chlorinated SRFA

sample. Ultrafiltration was used to flush out most of the

inorganic ions in the chlorinated SRFA sample. The objective

of this step was to remove chloride ions remaining after

chlorination, so that when chlorinated DBPs was degraded on

the AC to release chloride, the amount released could be seen

over the background level. Detailed information on the

ultrafiltration can be found in a previous study (Li et al., 2010).

For the iodinated SRFA sample preparation, the initial

concentrations of SRFA and iodine were 3 mg/L as C and

1.27 mg/L as I2, respectively. In natural waters, iodide is found

at concentrations of 0.5e212 mg/L (Moran et al., 2002), whereas

the higher concentration of iodine was used to magnify the

possible reactions and products. The reaction also lasted for

5 d at ambient temperature and no residual iodine was left

after 5 d.

In other research, inorganic chloramines have been repor-

ted to be reduced by AC to chloride (Bauer and Snoeyink, 1973).

It has been demonstrated that chlorination of some amino

compounds forms organic chloramines, which are one type of

DBPs in TOCl that could be reduced by AC (Li et al., 2010).

Therefore, eight amino compounds were used as model

compounds, includingglycine, glycylglycine, cytosine, leucine,

methylamine, adenine, phenylalanine, and tryptophan. For

the preparation of brominated model compounds, 1 mM of

each amino compound was dissolved in a 12.5 mM bromine

solution (2mg/L as Br2). The pH of themixture was around 7.2.

wat e r r e s e a r c h 4 5 ( 2 0 1 1 ) 1 2 2 9e1 2 3 7 1231

After a reaction time of 2 h at ambient temperature, the

samples were measured for bromine residuals, and no

bromine residuals were left. Chlorinated and iodinated amino

compounds were prepared with a similar procedure. Briefly,

1 mM of each amino compound was dissolved in a 0.1 mM

chlorine solution (7.1 mg/L as Cl2) or a 5 mM iodine solution

(1.27 mg/L as I2). After a reaction time of 2 h at ambient

temperature, no chlorine or iodine residuals were left.

Three real water samples were also evaluated, including

twowastewater samples fromHong Kong (one from a primary

effluent and the other from a secondary effluent), and one

swimming pool water sample (from a Hong Kong indoor

swimming pool with a water temperature of w24.5 �C). Thecharacteristics and chlorination of the three water samples

are shown in the Supplementary Information. These chlori-

nated water samples were expected to contain different levels

of organic chloramines/bromamines and thus exhibit

different TOCl/TOBr concentrations when measured with

original and ozonated AC columns.

2.2. Measurement of TOCl, TOBr, TOI, Cl�, Br�, and I�

TOCl, TOBr, and TOI were determined using an AC adsorption

and pyrolysis method with off-line ion chromatography as

a halide detector (Hua and Reckhow, 2006). Sample prepara-

tion and AC adsorption followed Standard Method 5320B

(APHA et al., 1995). Pre-packed AC columns were obtained

from Mitsubishi Corporation. Halogenated samples were

adjusted to pH 2 with nitric acid and then passed through two

consecutive AC columns in a 3-channel adsorption module

(TXA03C, Mitsubishi). After that, the AC columns were

washed with 5 mL of 5000 mg/L as NO3� of potassium nitrate

(with a flow rate of 3mL/min) to remove inorganic halides and

were subsequently subjected to pyrolysis at 1000 �C with an

AQF-100 automatic quick furnace (Mitsubishi). The hydrogen

halide and halogen gases from the pyrolysis unit were trapped

by 5 mL of 0.003% hydrogen peroxide absorbent (freshly made

daily), which contained 2 mg/L of phosphate serving as an

internal standard to estimate the volume variations induced

by the GA-100 gas absorption unit (Mitsubishi). An ICS-3000

ion chromatography system (Dionex, Sunnyvale, CA) equip-

ped with an IonPac analytical column (AS19, 4 � 250 mm) and

a guard column (AG19, 4 � 50 mm) was used. The eluent was

generated by an EGC potassium hydroxide cartridge at a flow

rate of 1 mL/min. Chloride and Br� ions were determined with

an isocratic eluent of 10mMKOH from 0 to 10min followed by

a linear gradient eluent of 10e45 mM KOH from 10 to 25 min.

Iodide was determined with an isocratic eluent of 10 mM KOH

from 0 to 10 min followed by a linear gradient eluent of

10e58 mM KOH from 10 to 40 min. The concentrations of the

halides were quantified with a conductivity detector. The

practical quantitation limits for TOCl, TOBr, and TOI in a 40-

mL sample were 0.002 mg/L as Cl, 0.002 mg/L as Br, and

0.009 mg/L as I, respectively.

The concentrations of Cl�, Br�, and I� in a sample were

measured with the same ion chromatograph under the same

instrument settings. The practical quantitation limits for Cl�,Br�, and I� were 0.010, 0.010, and 0.050mg/L, respectively. The

relative standard deviations (RSDs) for the Cl� measurement

in 7 aliquots of a standard NaCl solution (0.010 mg/L as Cl� in

ultrapure water) and a chlorinated SRFA sample were 0.05%

and 0.60%, respectively. The RSDs for the Br� measurement in

7 aliquots of a standard NaBr solution (0.010 mg/L as Br� in

ultrapure water) and a brominated SRFA sample were 0.10%

and 0.75%, respectively. The RSDs for the I� measurement in 7

aliquots of a standard KI solution (0.050mg/L as I� in ultrapure

water) and an iodinated SRFA sample were 0.05% and 0.55%,

respectively.

Unless otherwise specified, triplicates of a sample were

analyzed for TOCl, TOBr, TOI, Cl�, Br�, and I�.

2.3. Reactions of halogenated samples with AC

Two 20-mL aliquots of a brominated DBP sample were

collected in two vials. One aliquot was used as a control, and

the other aliquot was allowed to react with AC. The AC was

purchased from Mitsubishi (coconut-based with particle sizes

of 100e200 mesh and a very low halide background of �0.4 mg

Cl�/40 mg AC), and was the same as the one packed in the AC

columns for TOX analyses. The aliquot was spiked with 40 mg

of the AC and was adjusted to pH 2 immediately (to simulate

the TOX measurement procedure). After a contact time of

5 min, the aliquot was filtered with a syringe coupled with

a 0.45 mm Durapore PVDF membrane filter (Millipore Corpo-

ration). The filtrate was collected and adjusted back to pH 7 for

determination of the Br� concentration. As the nitrate peak

overlapped with the Br� peak in the ion chromatograph,

a chloride solutionwas used to substitute for the nitratewash.

The syringe filter was rinsed three times (to rinse out all the

Br� in the AC and the syringe filter), each time with 10 mL of

6008 mg/L of a chloride solution, which was used to simulate

5000 mg/L of a nitrate solution, and the Br� concentration in

each filtrate (10 mL) was measured. Finally, the total Br�

concentration in the aliquot after contact with the AC was

calculated by combining the Br� concentrations in all the

filtrates. It was designated as the one with a contact time of

“5 min” with the AC. For the aliquot used for a control, it was

treated in the sameway, except that no ACwas used, and thus

was designated as the one with a contact time of “0 min” with

the AC. Since the AC might contain some rinsable Br� ions,

another control was conducted as follows: 20 mL of ultrapure

water was spiked with 40mg of the AC. After a contact time of

5 min, the sample was filtered with a syringe coupled with

a 0.45 mmDurapore PVDFmembrane filter, followed by rinsing

the syringe filter with 10 � 3 mL of a 6008 mg/L chloride

solution. The chloride solution was found not to contain any

measurable Br� ions. The Br� concentrations in all the filtrates

were measured and combined. The total Br� concentration

would be deducted from the Br� concentration in the aliquot

with a contact time of 5 min with the AC. The iodinated and

(ultrafiltered) chlorinated DBP samples were treated with the

similar procedures, except that the 5000 mg/L nitrate solution

was used to rinse the syringe filter.

2.4. Treatment of AC

The results in a previous study showed that AC treated with

ozone minimized the reduction of a portion of the TOCl to Cl�

(Li et al., 2010). In this study, ozone gas from an ozone

generator (10K-2U, Enaly) was absorbed in ultrapure water to

0 min

5 min

0 min

5 min

1.6

1.2

0.8

0.4

0.0

2.0

Cl− o

r B

r−

co

nc. (m

g/L

)

Cl−

conc. in

chlorinated SRFA

+ AC

Br− conc. in

brominated SRFA

+ AC

Fig. 2 e ClL and BrL concentrations in the brominated

wat e r r e s e a r c h 4 5 ( 2 0 1 1 ) 1 2 2 9e1 2 3 71232

prepare a w15 mg/L ozone stock solution, which was diluted

immediately to prepare ozone solutions ranging from 0.25 to

10 mg/L. Ten mL of each diluted ozone solution was passed

through an AC column immediately at a flow rate of 2mL/min.

It was found that 10 mL of a 2.4 mg/L ozone solution was the

optimal ozone dose for treating the AC (Fig. 1). Accordingly, to

prepare an ozonated AC column, 10 mL of a 2.4 mg/L ozone

solution was passed through an AC column immediately at

a flow rate of 2 mL/min. The ozonated AC column was kept in

a fume hood for over 24 h until used for TOX analysis. The

TOCl, TOBr and TOI recoveries with the ozonated and original

AC columns were tested with monochloroacetic acid, mono-

bromoacetic acid and monoiodoacetic acid, which have been

used to test the recoveries by Hua and Reckhow (2006).

SRFA and the ultrafiltered chlorinated SRFA samples after

a contact time of 0 or 5 min with AC.

3. Results and discussion

3.1. Reactions of brominated SRFA with AC

Fig. 2 shows the Br� concentrations in the brominated SRFA

sample before and after reaction with the AC. The Br�

concentration in the brominated SRFA sample was 1.70 mg/L

and the measured TOBr concentration was 0.28 mg/L as Br.

After reaction with the AC, the Br� concentration in the

brominated SRFA sample increased to 1.73 mg/L. Such an

increase was not significant ( p > 0.05) as shown in

Supplementary InformationTableS1. ThenetBr� increment in

the 5-min contact was 0.03 mg/L, which means that 0.03 mg/L

of TOBr may have been reduced to Br� in 5 min. Considering

that the measured TOBr concentration in brominated SRFA

sample was 0.28 mg/L as Br, the measurement error for the

brominated SRFA sample with the standard method may be

estimated as 0.03/(0.28 þ 0.03) ¼ 9.8%.

As a comparison, the ultrafiltered chlorinated SRFA sample

was also used to react with the AC (Fig. 2). After a contact time

of 5 min, the Cl� concentration in the ultrafiltered sample

increased from 0.18 to 0.31 mg/L, indicating a significant

0.30

0.40

0.20

0.10

0 2 4 6 8 10

O3 concentration (mg/L)

TO

Cl o

r T

OB

rco

nc. (m

g/L

a

sC

lo

rB

r)

TOCl

TOBr

Fig. 1 e TOCl and TOBr levels in a chlorinated SRFA sample

measured with AC columns that were treated with

different ozone doses (10 mL). The chlorinated SRFA

sample was prepared as follows: SRFA 3 mg/L as C, BrL

0.4 mg/L, alkalinity 90 mg/L as CaCO3, chlorine dose 5 mg/L

as Cl2, and chlorine contact time 5 d (with no free chlorine

residual at end of 5 d).

increase ( p < 0.05). The net Cl� increment in 5 min was

0.13 mg/L. The measured TOCl concentration in the ultra-

filtered sample was 0.42 mg/L as Cl, thus the measurement

error for the ultrafiltered sample with the standard method

can be estimated as 0.13/(0.42 þ 0.13) ¼ 23.6%. The results

show that the chlorinated SRFA can be reduced by AC,

whereas it seems as if the TOBr reduction, at least for the

brominated SRFA, occurred in a less extent. It needs pointing

out that, to observe the Cl� increment from the reduction of

chlorinated SRFA by the AC, the use of the “ultrafiltered”

chlorinated SRFA sample to react with the AC was a choice

with no alternative because of the high Cl� concentration in

the original sample. As shown later in Section 3.3, the TOCl

concentrations in the “original” chlorinated SRFA sample

measured with AC and ozonated AC were 0.484 and 0.600 mg/

L as Cl, respectively. The net TOCl increment corresponded an

improvement of 19.3%, which further confirms that the

reduction of the TOBr in the brominated SRFA occurred in

a less extent than that of the TOCl in the chlorinated SRFA.

Finally, the reduction of the TOI in the iodinated SRFA sample

by the AC was barely detectable.

3.2. Reactions of brominated amino compounds with AC

The concentrations of the brominated amino compounds

measured as TOBr are shown in Table 1. As a comparison, the

concentrations of chlorinated and iodinated amino

compounds measured as TOCl and TOI, respectively, are also

shown in this table. For brominated cytosine, TOBr was

detected at a significant level (0.772 mg/L as Br), whereas the

TOBr concentrations of the other brominated amino

compounds were below 0.10 mg/L as Br. Considering that the

brominatedamino compoundswerepreparedusing a bromine

solution of 2 mg/L as Br2, cytosine had a 38.6% bromine utili-

zation, whereas the other amino compounds had <4%

bromineutilization. The results in Table 1 also showed that the

TOX concentrations in both brominated and chlorinated

cytosine were significant.

Among the eight brominated amino compounds, after a 5-

min contact with AC, the Br� concentrations increased obvi-

ously in five samples (and presented no discernible changes in

Table 1 e TOCl, TOBr and TOI in halogenated amino compounds.

Aminocompound

Molecularweight

TOCl (mg/L as Cl)in chlorinated

amino compound

TOBr (mg/L as Br)in brominated

amino compound

TOI (mg/L as I)in iodinated

amino compound

Glycine 75.07 0.031 0.024 0.051

Methylamine 31.06 0.002 0.015 0.013

Leucine 131.17 0.007 0.044 0.035

Glycylglycine 132.12 0.339 0.056 0.090

Cytosine 111.10 1.218 0.772 0.155

Adenine 135.13 0.031 0.023 0.028

Phenylalanine 165.19 0.009 0.064 0.088

Tryptophan 204.20 0.049 0.037 <0.009

wat e r r e s e a r c h 4 5 ( 2 0 1 1 ) 1 2 2 9e1 2 3 7 1233

other threesamples). Fig. 3ashowstheBr� concentrations inthe

brominated glycine, glycylglycine, leucine, phenylalanine, and

cytosine samples. After a 5-min contact with AC, the Br�

concentrations in the five samples increased significantly

( p < 0.05). The net Br� increments in 5 min were 0.056, 0.119,

0.066, 0.082, and 0.121 mg/L, respectively. For the brominated

glycylglycine, phenylalanine, and cytosine, the Br� increments

weremore significant. Because themeasured concentrations of

TOBr for the brominated glycylglycine, phenylalanine, and

cytosine samples were 0.056, 0.064, and 0.772 mg/L as Br,

respectively (see Table 1), the measurement errors for the

brominated amino compounds with the standard method can

be calculated as 68.0%, 56.2% and 13.5%, respectively. For the

brominated

glycine

+ AC

brominated

glycylglycine

+ AC

brominated

leucine

+ AC

brominated

phenylalanine

+ AC

brominated

cytosine

+ AC

2.4

2.0

1.6

1.2

2.8

4.2

2.8

1.4

0.0

5.6

Cl conc. in

chlorinated

glycine + AC

Cl conc. in

chlorinated

glycylglycine

+ AC

Cl conc. in

chlorinated

cytosine + AC

l conc. in

iodinated

glycine + AC

l conc. in

iodinated

glycylglycine

+ AC

0 min

5 min

0 min

5 min

0 min

5 min

0 min

5 min

0 min

5 min

0 min 5 min 0 min 5 min

0 min

5 min

0 min

5 min

0 min

5 min

Br

− c

on

c.

(m

g/L

)C

l− or

I−co

nc

. (m

g/L

)

a

b

Fig. 3 e (a) BrL concentrations in the brominated amino

compound samples after a contact time of 0 or 5 min with

the AC. (b) ClL and IL concentrations in the chlorinated and

iodinated amino compound samples after a contact time of

0 or 5 min with the AC.

brominatedglycylglycineandphenylalanine, themeasurement

errorswere relativelyhighbecause theamounts ofTOBr formed

were so low. Nonetheless, this experiment demonstrated that

some of the brominated amino compounds could be reduced in

part by the AC.

During disinfection, amino compounds may react with

bromine to form organic bromamines:

R2NH þ HOBr / R2NBr þ H2O

RNH2 þ 2HOBr / RNBr2 þ 2H2O

Bauer and Snoeyink (1973) studied the reactions of inor-

ganic chloramines with AC. Zhang and Minear (2006) and Li

et al. (2010) examined the reactions of organic chloramines

with AC. Likewise, the reactions of some organic bromamines

with AC are proposed:

R2NBr þ H2O þ C* / R2NH þ C*O þ Hþ þ Br�

RNBr2 þ H2O þ C* / 0.5RN]NR þ C*O þ 2Hþ þ 2Br�

where C* and C*O represent the carbon surface and

a surface oxide, respectively.

In order to find the trend of halogenated DBP reactionswith

AC, some chlorinated and iodinated amino compounds were

also evaluated. Fig. 3b shows the Cl� concentrations in the

chlorinated glycine, glycylglycine, and cytosine samples

before and after a 5-min contact with the AC. As shown in

Fig. 3b, the net Cl� increases in 5 min were 0.608, 0.238,

0.413 mg/L, respectively. Because the measured TOCl concen-

trations of chlorinated glycine, glycylglycine, and cytosine

samples were 0.03, 0.34 and 1.22 mg/L as Cl, respectively, the

measurement errors for the chlorinated amino compounds

with the standard method were 95.3%, 41.3%, and 25.3%

respectively. The I� concentrations in the iodinated glycine,

glycylglycine, and cytosine samples before and after a 5-min

contact with the AC were also examined. The net I� increases

in 5min were 0.001, 0.012, and 0.011mg/L, respectively, which

were not significant ( p > 0.05).

In terms of the relative reduction of TOCl, TOBr, and TOI,

some instances of TOBr and all of the TOI examples for the

amino compounds showed insignificant reductions. The best

wat e r r e s e a r c h 4 5 ( 2 0 1 1 ) 1 2 2 9e1 2 3 71234

comparisons (at least for TOCl and TOBr) were for glycine,

glycylglycine, and cytosine, where the reductions were higher

for TOCl. Nonetheless, the results suggested that some of the

brominated amino compounds could be reduced by the AC,

but the extent of the reduction was lower than that of the

chlorinated amino compounds.

3.3. Improvement of the TOBr measurement withozonated AC

The reductive property of the AC was demonstrated to cause

the systematic error in the TOCl measurement, so the AC

columns were slightly oxidized by ozone with the same

procedure described in the previous study (Li et al., 2010).

When either the ozonated or original AC columnswere used in

the TOX measurement procedure, the TOCl, TOBr and TOI

recoveries with monochloroacetic acid, monobromoacetic

acid and monoiodoacetic acid were all within 93.6%e99.2%,

whichwere comparable to the recoveries reported by Hua and

Reckhow (2006). The results indicated that slight oxidation of

theACwith ozone still wellmaintained its adsorption capacity

for TOCl, TOBr and TOI.

Then the ozonated AC columnswere used to comparewith

the original AC columns in the TOBr analyses. As shown in

Fig. 4, the brominated SRFA sample and five brominated

amino compounds (glycine, glycylglycine, leucine, phenylal-

anine, cytosine) were used to examine the adsorption effi-

ciency and reductive property of the ozonatedAC. Chlorinated

2.4

2.0

1.6

1.2

0.8

0.4

0.0

chlorinated

cytosine

brominated

cytosine

Iodina

cytos

TO

Cl, T

OB

r o

r T

OI

co

nc.

(m

g/L

as

Cl,

B

r o

r I)

ozonated ACAC

0.08

0.04

0.00

0.12

brominated

glycine

brominated

glycylglycine

bromin

leucin

TO

Br c

on

c.

(m

g/L

as

Br)

a

b

Fig. 4 e (a) TOBr concentrations in different brominated amino co

ACs. (b) TOCl, TOBr, and TOI concentrations in different halogena

and ozonated ACs.

cytosine, iodinated cytosine, and chlorinated SRFA samples

were also measured for comparison.

As shown in Fig. 4a, the TOBr concentrations in the bromi-

natedglycine samplemeasuredwith theoriginal andozonated

AC columns were 0.024 � 0.002 and 0.030 � 0.003 mg/L as Br,

respectively; the difference was 0.006 mg/L as Br. The TOBr

concentrations in the brominated glycylglycine sample

measured with the original and ozonated AC columns were

0.056 � 0.003 and 0.100� 0.010 mg/L as Br, respectively, where

the difference (0.044mg/L as Br) was substantial. Likewise, the

TOBr concentrations in the brominated leucine sample

measured with the original and ozonated AC columns were

0.044 � 0.007 and 0.065 � 0.008 mg/L as Br, respectively, with

a difference of 0.022 mg/L as Br; in the brominated phenylala-

nine sample the TOBr concentrations were 0.064 � 0.007 and

0.098 � 0.007 mg/L as Br, respectively, with a difference of

0.034 mg/L as Br; and in the brominated cytosine sample the

TOBr concentrationswere 0.772� 0.032 and 0.925� 0.098mg/L

as Br, respectively, with a difference of 0.153 mg/L as Br.

Statistical analyses show that the TOBr concentrations in the

five brominated amino compounds measured with the ozo-

nated AC columns were significantly higher than the corre-

sponding ones measured with the original AC columns

( p < 0.05). These results suggested that the slight oxidation of

the AC with ozone might effectively inhibit its reductive

property on the brominated amino compounds. It is of note

that the effect of the ozonated AC was different among

different amino acids, which may be ascribed to the different

0.8

0.2

0.0

0.6

0.4

ted

ine

chlorinated

SRFA

brominated

SRFA

TO

Cl o

r T

OB

rco

nc.

(m

g/L

as

Cl o

rB

r)

0.8

0.2

0.0

1.0

0.6

0.4

ated

e

brominated

phenylalanine

brominated

cytosine

TO

Br c

on

c. (m

g/L

as

Br)

ozonated ACAC

mpound samplesmeasuredwith the original and ozonated

ted cytosine and SRFA samples measured with the original

Fig. 5 e (a) BrL concentrations in the brominated amino

compound samples after a contact time of 0 or 5 min with

the original and ozonated ACs. (b) ClL and BrL

concentrations in the chlorinated SRFA, brominated SRFA,

chlorinated cytosine, and brominated cytosine samples

after a contact time of 0 or 5 min with the original and

ozonated ACs.

wat e r r e s e a r c h 4 5 ( 2 0 1 1 ) 1 2 2 9e1 2 3 7 1235

NeBr bond strengths and steric effects of the formed organic

bromamines.

Fig. 4b compares the impact of ozonation of the AC on the

TOCl, TOBr and TOI concentrations of halogenated cytosine.

The TOCl concentrations in the chlorinated cytosine samples

measured with the original and ozonated AC columns were

1.56 � 0.097 and 1.97 � 0.082 mg/L as Cl, respectively (a

significant increase, p < 0.05). The difference was 0.417 mg/L

as Cl. On the basis of the TOCl concentration measured with

the ozonated AC, the incremental improvement can be

calculated as 0.417/(1.56 þ 0.417) ¼ 21.1%. Likewise, the TOBr

concentrations in the brominated cytosine sample measured

with the original and ozonated AC columns were 0.772� 0.032

and 0.925 � 0.098 mg/L as Br, respectively (a significant

increase, p < 0.05), the net increment was 0.153 mg/L as Br,

and the improvement was 16.5%. However, the TOI concen-

trations in the iodinated cytosine sample measured with the

original and ozonated AC columns were 0.155 � 0.010 and

0.170� 0.013mg/L as I, respectively (not a significant increase,

p > 0.05), the net increment was 0.015 mg/L as I, and the

improvement was only 8.8%. The TOCl and TOBr concentra-

tions in chlorinated and brominated SRFA samples were also

compared in Fig. 4b. The concentrations of TOCl measured

with the original and ozonated AC columns were

0.484� 0.044mg/L and 0.600� 0.024mg/L as Cl, respectively (a

significant increase, p < 0.05). The net improvement was

19.3%. The concentrations of TOBrmeasured with the original

and ozonated AC columns were 0.278 � 0.007 and

0.300 � 0.015 mg/L as Br, respectively (a significant increase,

p < 0.05). The net improvement was 7.3%. The results showed

a similar impact of the AC column on the TOX reduction:

TOI < TOBr < TOCl. The reduction of TOCl, TOBr, and TOI by

the AC was likely associated with organic haloamines, which

may inherit certain oxidation power from the precursor

halogens (whose oxidation potentials are in the order of

HOI < HOBr < HOCl).

To confirm the reduction inhibition with the ozonated AC,

the bromide concentrations of the brominated amino

compound and SRFA samples were tested before and after

these samples reacted with the original and ozonated ACs.

Fig. 5a shows the Br� concentrations in different brominated

amino compound samples before and after reactions with the

ACs. After a contact time of 5min, the Br� concentration in the

brominated glycine sample with the original AC increased

from 2.35 to 2.41 mg/L (not a significant increase, p > 0.05),

whereas in the sample with the ozonated AC it was 2.38 mg/L.

Alternatively, the Br� concentration in the brominated gly-

cylglycine sample with the original AC increased from 2.32 to

2.44 mg/L (a significant increase, p < 0.05), whereas in the

sample with the ozonated AC it was less (2.38 mg/L). The Br�

decrement between the original and ozonated ACs was

0.06 mg/L, which was close to the corresponding TOBr incre-

ment (0.05 mg/L as Br, Fig. 4a). Similar results were obtained

with brominated leucine and phenylalanine samples.

As shown in Fig. 5b, the Br� concentration in the bromi-

nated SRFA sample with the original AC increased from

1.68 mg/L to 1.74 mg/L (not a significant increase, p > 0.05),

whereas in the samplewith the ozonated AC (1.69mg/L) it was

close to the initial Br� concentration. Alternatively, the Cl�

concentration in the ultrafiltered chlorinated SRFA sample

with the original AC increased from 0.320 to 0.427 mg/L (a

significant increase, p < 0.05), whereas in the sample with the

ozonated AC (0.350 mg/L) it was close to the initial Cl�

concentration. Similar results were obtained with the chlori-

nated and brominated cytosine samples.

The results demonstrated that the ozonated AC inhibited

the reduction of TOCl and TOBr. However, the impact on TOBr

was much less than that on TOCl. This may have been due (in

part) to there being (in general) much less reduction of TOBr

than TOCl on the original AC.

3.4. Measurement of TOCl and TOBr concentrationswith ozonated AC for chlorinated wastewater effluents andswimming pool water samples

Two chlorinated wastewater effluent samples and one chlo-

rinated swimming pool water samplewere used as alternative

organic matter sources to evaluate the TOX adsorption and

reduction inhibition by the ozonated AC. After treatment,

TOCl and TOBr concentrations in all water samples were

measured with the original and ozonated AC columns. As

shown in Fig. 6, the TOCl concentrations were 0.268 � 0.030

and 0.346 � 0.033 mg/L as Cl respectively in the primary

effluent (a significant increase, p< 0.05), and 0.176� 0.007 and

0.204 � 0.018 mg/L as Cl respectively in the secondary effluent

ozonated AC AC

0.8

0.6

0.4

0.2

0.0

1.0

1.2

TOCl TOBr TOCl TOBr

chlorinated primary

wastewater effluent

TO

Cl o

r T

OB

rco

nc

. (m

g/L

a

s C

l o

rB

r)

TOCl TOBr

chlorinated secondary

wastewater effluent

chlorinated swimming

pool water

Fig. 6 e TOCl and TOBr concentrations in the chlorinated

wastewater primary effluent, chlorinated wastewater

secondary effluent, and chlorinated swimming pool water

samples measured with the original and ozonated ACs.

wat e r r e s e a r c h 4 5 ( 2 0 1 1 ) 1 2 2 9e1 2 3 71236

(a significant increase, p < 0.05). The net increments in TOCl

concentrations were 0.078 and 0.028 mg/L as Cl, respectively.

The error bars slightly overlapped for the TOClmeasurements

for the secondary effluent. The TOBr concentrations were

0.142 � 0.011 and 0.195 � 0.015 mg/L as Br respectively in the

primary effluent (a significant increase, p < 0.05), and

0.447 � 0.035 and 0.487 � 0.020 mg/L as Br respectively in the

secondary effluent (not a significant increase, p > 0.05). The

net increments in TOBr concentrations were 0.053 and

0.040 mg/L as Br, respectively. The error bars partially over-

lapped for the TOBrmeasurements for the secondary effluent.

The results showed that the TOCl and TOBr concentrations

measured with the ozonated AC increased significantly,

especially for the chlorinated primary effluent sample.

Because the ammonia concentration in the primary effluent

wasmuch higher than that in the secondary effluent, the N/Br

ratio was much higher in the primary effluent. Galal-Gorchev

and Morris (1965) demonstrated that the formation of inor-

ganic bromamine species was impacted by the N/Br ratio. This

and differences in the organic matter makeup (e.g., organic

nitrogen content) of the two wastewater effluents may have

also impacted organic haloamine formation. Certain organic

haloamines are considered to be important compounds

reduced by AC.

As shown in Fig. 6, the TOCl concentrations in the bromide-

spiked swimming pool water sample were 0.966 � 0.019 and

1.002 � 0.022 mg/L as Cl, respectively (a significant increase,

p < 0.05), and the TOBr concentrations were 0.089 � 0.008 and

0.091 � 0.004 mg/L as Br, respectively (not a significant

increase, p > 0.05). The net increments were 0.036 mg/L as Cl

and 0.002 mg/L as Br. However, the error bars partially over-

lapped for both TOCl and TOBr. Compared with the primary

wastewater effluent sample, the increments for TOCl and

TOBrwere relatively small. The difference in resultsmay have

been due (in part) to the low concentrations of the ammonia

and organic nitrogen content in the swimming pool water

sample, where breakpoint chlorination should have been

achieved. The results again suggest the importance of organic

haloamines to the TOX reduction by AC.

4. Conclusions

The results showed that brominated DBPs may be reduced by

the AC used in the TOX standard method, but the reduction

was lower than that of the chlorinated DBPs. Around 10% of

the TOBr in the brominated SRFA sample was reduced by the

AC, which was less than what was observed with the chlori-

nated SRFA (around 20%). The reduction of the TOI in the

iodinated SRFA by the AC was negligible. A similar trend was

observed for some halogenated amino compounds, i.e., the

impact of the AC on the TOX reduction was in the order of

TOI < TOBr < TOCl. The reductions in TOBr by the AC were

significant in the brominated glycylglycine, phenylalanine,

and cytosine samples, leading to the measurement errors

with the standard method up to 68.0%, 56.2% and 13.5%,

respectively. TOBr measurements may be improved by using

the ozonated AC, which can minimize the reduction of the

brominated DBPs during the adsorption procedure in cases

where it occurred. The TOCl and TOBr concentrations in the

chlorinated primary wastewater effluent were improved

dramatically when measured with the ozonated AC columns.

The results suggest the importance of organic haloamines to

the TOX reduction by the AC.

Acknowledgments

The work was supported by a grant from the Research Grants

Council of the Hong Kong Special Administrative Region,

China (Project No. HKUST622808).

Appendix. Supplementary information

Supplementary information associatedwith this article can be

found, in the online version, at doi:10.1016/j.watres.2010.09.

038.

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