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Effect of water chemistry on disinfection by-product formation in the complex surface water system
Accepted Manuscript Impact of water chemistry on disinfection by-products formation in the complex surface water system
Rongjie Hao, Yan Zhang, Tingting Du, Li Yang, Adeyemi S. Adeleye, Yao Li PII:
S0045-6535(16)31746-5
DOI:
10.1016/j.chemosphere.2016.12.034
Reference:
CHEM 18490
To appear in:
Chemosphere
Received Date:
28 August 2016
Revised Date:
05 December 2016
Accepted Date:
07 December 2016
Please cite this article as: Rongjie Hao, Yan Zhang, Tingting Du, Li Yang, Adeyemi S. Adeleye, Yao Li, Impact of water chemistry on disinfection by-products formation in the complex surface water system, Chemosphere (2016), doi: 10.1016/j.chemosphere.2016.12.034
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ACCEPTED MANUSCRIPT Highlights
High concentrations of DBPs were formed in the discharge Zone of Bohai Sea.
DBPs formation was highly affected by the combine water composition.
Br− and Cl− concentrations may highly affect the formation of Br-DBPs.
Compared to the chloramination, much more DBPs were formed with chlorination disinfection.
ACCEPTED MANUSCRIPT
1
Impact of water chemistry on disinfection by-products
2
formation in the complex surface water system
3 4
Rongjie Hao,1 Yan Zhang,1 Tingting Du,1 Li Yang,1 Adeyemi S. Adeleye,2 Yao Li1*
5 6
1 College of Environmental Science and Engineering/Ministry of Education Key Laboratory of
7
Pollution Processes and Environmental Criteria/Tianjin Key Laboratory of Environmental
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Remediation and Pollution Control, Nankai University, Tong Yan Road 38, Tianjin 300350, China
9
2 Bren School of Environmental Science and Management, University of California, Santa
10
Barbara, California 93106, United States
11 12 13 14
*To whom correspondence may be addressed: (Phone/fax) 86-22-2350-1117; (e-mail)
15
[email protected].
16 17
ACCEPTED MANUSCRIPT 18
Abstract
19
The relationship between the disinfection by-products (DBPs) formed with
20
chlorination and chloramination techniques, and the water chemistry of Haihe River
21
was compared. Samples were collected at 28 different points within the mainstream
22
and tributaries of the river. The DBPs investigated include trihalomethanes (THMs),
23
haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones (HKs) and
24
trichloronitromethane (TCNM). THMs formed when samples were chlorinated mostly
25
exceeded 100 μg/L and 600 μg/L in the mainstream, tributaries and in the estuary,
26
respectively. A similar trend was obtained for HAAs whose concentrations exceeded
27
150 μg/L in almost all samples. The amounts of DBPs formed when samples were
28
chloraminated were much lower than when chlorination was employed. The
29
concentrations and species of THMs and HAAs in samples collected from sites
30
nearby the estuary were different from those in samples collected from the
31
mainstream, which may be due to high concentrations of Cl− and Br−. Although
32
natural organic matter (NOM) is the major cause of DBPs formation during water
33
disinfection, this study shows that other water chemistry factors, such as salt
34
composition and concentrations, may also significantly affect the formation of DBPs
35
in natural aquatic systems.
36 37
Keywords：disinfection by-products, chlorination and chloramination, surface
38
water, water chemistry
39
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1. Introduction
41
Disinfection has long been widely used to kill different pathogens in drinking
42
water. However, it is also responsible for the formation of disinfection by-products
43
(DBPs), which may have serious negative effects on human health (Zhang et al.,
44
2000; Richardson et al., 2003; Krasner et al., 2006). DBPs were first described in
45
1974 (Rook, 1974), and have been studied for more than 40 years. Several studies
46
have investigated the different types of DBPs—known and unknown— that may form
47
in natural waters, and their effects to humans. Trihalomethanes (THMs) and
48
haloacetic acids (HAAs), two most prevalent priority DBPs found in chlorinated
49
drinking water worldwide (Zeng, et al., 2016), are typically used as the proxies for
50
estimating DBPs amounts (Krasner and Aieta, 1989; Pontius, 1993). Meanwhile,
51
during disinfection with chloramine, some organic chloramines (N-DBPs) are formed
52
(Westerhoff and Mash, 2002; Yang and Shang, 2004), which were shown to be more
53
toxic than THMs and HAAs. A new series of brominated and iodinated anilines were
54
recently identified, which may also improve the cognition of DBPs and their effect on
55
human being (Zhang et al., 2008; Ding and Zhang, 2009; Li et al., 2010, 2011).
56
The formation of all these traditional and/or new DBPs in natural systems may
57
be greatly affected by water chemistry and compositions. Water components such as
58
natural organic materials (NOMs), chlorides and bromides, salts, and N-containing
59
compounds, are present at different levels in many sources of drinking water, and they
60
can significantly affect the formation of DBPs (Kim and Yu, 2005; Bougeard et al.,
61
2010). For example, since the NOM is the precursor of DBPs, the composition and
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the amount of NOM present determines the species and quantity of DBPs that will
63
form (Fang et al., 2010; Richardson et al., 2003). In addition, bromide in the water
64
may promote the formation of brominated DBPs (Zhai et al., 2011, 2014). Salts may
65
not directly cause the formation of DBPs, but they affect the concentrations and type
66
of DBPs formed in saline water systems (Pan et al., 2016). The individual effects of
67
each of these factors (salts, NOM, etc.) on the formation of DBPs have been
68
comprehensively studied (Chellam, 2000; Bolto et al., 2004; Sharp et al., 2006;
69
Matilainen et al., 2010), but the impact of the different factors in the complex water
70
systems remains unclear and needs to be investigated.
71
Haihe River, which is located in Tianjin, an essential industrial and high-tech
72
production city of China, is one of the largest rivers in northern China and it
73
discharges into the Bohai Sea. The river receives high inputs of domestic, industrial
74
and agricultural wastewater (Jin et al., 2004), and consists of a mainstream and many
75
tributaries, such as Ziya river, Xinkai river, the Beiyun river, the Nanyun river,
76
Fuxing River, and so on (Yang et al., 2005). Haihe River covers a distance of 1090
77
km around zones of different land-uses; and with so many tributaries, its chemistry
78
and composition (such as NOM concentrations, salts, and N-containing materials) at
79
different points vary widely. In particular, formation of new DBPs have been
80
observed in its tributaries, which makes it an ideal natural system for DBPs formation
81
studies (Yang and Zhang, 2013, 2014; Liu and Zhang, 2014). The possible input of
82
disinfectant into river with wastewater cannot be ignored. Besides, though some
83
saline locations on the Haihe were not suitable as a drinking water supply right now,
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the suitability of Haihe River as drinking water source in the future also need to be
85
evaluated due to growing demand for water in Northern China (The use of Haihe
86
River as a drinking water source was discontinued decades ago due to pollution.).
87
The major objective of this study was to investigate DBPs formation at different
88
points in Haihe River and to correlate DBPs formation with the properties of water in
89
a holistic manner. In this study Haihe River was divided into four distinct regions
90
based on the sampling positions and water chemistry. All DBPs, including THMs,
91
HAAs, haloacetonitriles (HANs), haloketones (HKs), and trichloronitromethane
92
(TCNM) were measured, and compared between two main disinfection methods—
93
chlorination and chloramination. The effects of water composition on DBPs formation
94
were also investigated within the different regions. In order to obtain a more obvious
95
comparison of the results in a short period of time, we have adopted higher amount of
96
disinfectant than that of the conventional dosage in the experimental procedures and
97
have not conducted DOC removal process.
98 99 100
Materials and methods 2.1. Sample collection and analyses
101
A total of 28 water samples were collected from Haihe River. There were 15
102
sampling sites in the mainstream, and 13 sampling sites in the eight tributaries. The
103
sampling sites locations are shown in Fig. 1.
104
Samples 1-8 were collected from the four tributaries upstream in Tianjin.
105
Samples 9-24 were collected around the mid-point of the main river, except samples
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15, 19, 21-23, which were from the surrounding tributaries around the mid-point.
107
Samples 25-28 were collected downstream around the point of discharge into the sea,
108
which is an estuary due to mixing with seawater. Based on the sampling position and
109
chemical composition, the entire sampling sites were broadly divided into four
110
regions: Region 1 consisted of samples 1-8, representing the samples collected from
111
upstream tributaries; Region 2 was made up of samples 9-18, representing the
112
samples mainly collected from the upper- and mid- mainstream (sample site 15 was
113
very close to the mainstream); Region 3 consisted of samples 19-23, which represents
114
samples collected mostly from the mid-stream tributaries; and region 4, consisting of
115
samples 24-28, representing the samples collected around the discharge zone of the
116
river into the Bohai Sea (Based on water composition, sample 24 was classified into
117
this region.). The chemical composition of region 4 is mainly affected by seawater
118
reflux, and regions 1-3 are mainly freshwaters.
119
After collection, samples were shipped to the laboratory and kept at 4 ◦C until the
120
samples were analyzed, which was less than 24 hours. Prior to analyses, all the
121
samples were filtered with a 0.45 µm membrane to eliminate particulate and
122
biological contaminants. The chlorinated/chloraminated filtered DI blank controls
123
were evaluated and no significant DBPs precursors were detected. After that,
124
dissolved organic carbon (DOC) concentration, UV absorbance at 254 nm (UV254),
125
bromide ion concentration, chloride ion concentration, NH3-N concentration, and
126
NO2-N concentration were determined. Specific UV absorbance (SUVA) was
127
calculated as UV254 divided by DOC.
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2.2. Chemicals and materials
130
Working solutions were prepared from reagent grade chemicals or stock
131
solutions. Dilution to target aqueous-phase concentrations was accomplished with
132
Milli-Q water. Stock of sodium hypochlorite (NaClO), which was purchased from
133
Sigma-Aldrich Corporation, was diluted to 900-1000 mg/L (as Cl2), stored in
134
aluminum foil-covered bottle, and kept at 4 ◦C until use. The stock solution was
135
periodically titrated by DPD/FAS titration before each experiment (APHA et al.,
136
1998). Monochloramine (NH2Cl) solution was prepared daily prior to experiments by
137
quickly adding equal volumes of ammonium chloride and sodium hypochlorite
138
solutions at a weight ratio of 4 mg/L Cl2 to 1 mg/L N-NH4+ with rapid stirring for 30
139
min (Yang et al., 2007). The solutions were then standardized by DPD/FAS titration
140
(APHA et al., 1998). All the DBP standards, including a mixture standard containing
141
THMs, HANs, HKs, and TCNM; a mixed standard of nine HAAs; and surrogate
142
standards were obtained from Sigma-Aldrich (Supelco, USA). Methyl–tert butyl ether
143
(MtBE) was obtained from AMP (Shanghai, China).
144 145
2.3. Experimental procedures
146
All the experiments (chlorination/chloramination) were carried out in 60 mL
147
amber-colored bottles. The dosage of chlorine (Cl2) was determined by the formula
148
approach shown in equation 1 (Krasner et al., 2008, 2009):
149
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Cl2 (mg/L)= 3*[mg/L dissolved organic carbon (DOC)] + 8*[mg/L NH3-N] +5*[mg/L NO2 -N] + 10 mg/L
Eq. 1
152 153 154
In chloramination tests, the dosage of monochloramine (NH2Cl) was determined by the formula shown in equation 2:
155 156
NH2Cl (mg/L) = 3*[mg/L DOC] + 5*[mg/L NO2-N]
Eq. 2
157 158
10 mM phosphate buffer was added into the samples to adjust the pH to 7, and all
159
samples were incubated in the dark at room temperature (25 ± 1 ◦C) for 3 d. After
160
incubation, reactions were quenched by adding ascorbic acid, and sample extraction
161
was immediately carried out with MtBE, as extractant and anhydrous sodium sulfate
162
as drying agent based on the liquid–liquid extraction process (Du et al., 2016). The
163
extracts were then analyzed via gas chromatography. All experimental conditions are
164
based on the formation potential test, and no water treatment was done to the Haihe
165
revier before the DBPs detection.
166 167
2.4. Analytical methods
168
Total organic carbon (TOC) concentrations were measured using a total organic
169
carbon analyzer (multi N/C 3100, Germany). UV254 was measured using a UV–visible
170
spectrophotometer (Shimadzu Scientific Instruments, USA). Cl− and Br− were
171
measured using an ion chromatograph (ICS1600, Thermo Fisher Scientific, USA).
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NH3-N concentrations were measured by Nessler’s reagent spectrophotometry (GB
173
7479-87), and NO2-N concentrations were measured by Spectrophotometric method
174
(GB 749-87). THMs, HKs and N-DBPs (HANs and TCNM) were analyzed via gas
175
chromatography (Agilent 6890N, Santa Clara, CA) connected to an electron capture
176
detector (GC-ECD) (Agilent Technologies, Santa Clara, CA) using USEPA Method
177
551.1. The column used was a HP-5 fused silica capillary column (30 mm×0.25 mm
178
I.D. with 0.25 μm film thickness, J&W Scientific, USA). The GC temperature
179
program consisted of an initial temperature of 35 °C for 6 min, ramped to 100 °C at
180
10 °C/min and held for 5 min, and finally, ramped to 200 °C at 20 °C/min and held
181
for 2 min. HAAs were also analyzed using the GC-ECD based on USEPA Method
182
552.2. The GC temperature program for HAAs analyses consisted of an initial
183
temperature of 35 °C for 10 min, ramped to 60 °C at 5°C/min, ramped to 75 °C at 2
184
°C/min and held for 2 min, ramped to 135 °C at 20 °C/min, and then ramped to 200
185
°C at 5 °C/min and held for 5 min.
186 187
3. Results and discussions
188
3.1. Water characteristic
189
The water properties at the 28 sampling points were summarized in Table 1. As
190
the primary DBPs precursor in aqueous systems, DOC is important for DBPs
191
formation. The DOC concentrations detected in regions 1-3 (i.e. upstream and mid-
192
stream sampling sites) ranged from 5.0 mg/L to 14.6 mg/L, and rank among the
193
highest DOC levels reported for Chinese inland waters (Gu et al., 2010; Hong et al.,
ACCEPTED MANUSCRIPT 194
2013, 2015). As can been seen in Table 1, DOC was particularly high in mid-stream
195
tributaries 15, 19, 21 and 23, which is primarily due to nearby contamination sources
196
such as wastewater treatment plant, hoggery and fish farms. Interestingly, the highest
197
average DOC (10.12 mg/L) was determined in region 4, around the delta of Bohai
198
Sea.
199
UV254 values obtained in this study were also relatively high compared to those
200
previously reported for Chinese key river systems (Wang et al., 2013). In general, the
201
average UV254 values increased downstream towards the Bohai bay. The highest value
202
0.23 cm-1 was found in sampling site 24. It should be noted that the correlation
203
between DOC and UV254 was not strong, which indicates the presence of different
204
types of NOM contents in different parts of the water. The spatial distribution of
205
SUVA was quite different from that of DOC and UV254. A high SUVA value (≥
206
4 L/mg·m) means a relatively high content of hydrophobic organic compounds, while
207
a low SUVA (≤ 3 L/mg·m) suggests a high percentage of hydrophilic organic
208
compounds (Zheng, 2016). The range of SUVA values obtained from the water
209
samples (1-2.92 L/mg·m) suggests the dominance of hydrophilic NOM types in Haihe
210
River.
211
Cl− and Br− levels in Haihe River increased with proximity to the Bohai Bay,
212
with a range of 20.2 mg/L to 6541.7 mg/L and 0.04 mg/L to 2.76 mg/L, respectively.
213
Sampling site 22, which was located at Laohai River, an old waterway of Haihe
214
River, had abnormally high Cl− concentration (254.8 mg/L) compared to the range
215
detected in the sample collected from neighboring waters (53.3-158 mg/L). NH3-N
ACCEPTED MANUSCRIPT 216
concentrations in more than 40% of the sampling sites were higher than 1 mg/L, the
217
Chinese surface water standard Ⅲ level. The highest NH3-N concentration (2.39
218
mg/L) was detected in Yueya River, which is higher than the Chinese surface water
219
standard Ⅴ level (2 mg/L). The high level of NH3-N is probably due to waste stream
220
discharges from the frozen food factory located around the waterbody. The highest
221
levels of NO2-N were detected in samples from Ziya River (an upstream tributary),
222
(Laohai River) (a mid-stream tributary) and all the samples from region 4 (the estuary
223
zone). All these variations in water properties are expected to play an important role
224
in the amount and types of DBPs that will be formed upon chlorination and
225
chloramination of water samples.
226 227
3.2. DBPs formation in Haihe River.
228
Five DBP types, including THMs, HAAs, HANs, HKs, and TCNM were
229
detected in all samples; and most of them could be detected with both chlorine and
230
chloramine disinfection procedures. The concentrations of individual THMs,
231
including CHCl3, CHCl2Br, CHClBr2 and CHBr3, and total THMs (TTHMs) are
232
shown in Fig. 2. THMs were detected in all the samples upon chlorination (Fig. 2a).
233
The concentrations of the THMs detected exceeded the maximum amount found in
234
typical water treatment plants in China (Ye, et al., 2009); and mostly exceeded the EU
235
and USEPA limits (80 μg/L and 100 μg/L, respectively) (Richardson et al., 2007). As
236
the DOC precursors were not removed with water treatment processes before the
237
DBPs test, the DBPs formation in this study can only reflect the DBPs formation
ACCEPTED MANUSCRIPT 238
potential in the Haihe river and the impact of water chemistry on the DBPs formation.
239
The average concentrations of THMs in the four regions were 144.3, 148.8, 128.9,
240
and 721.3 μg/L, respectively. The molar concentrations were 1.12, 1.17, 0.90 and 3.00
241
μmol/L. The TTHMs concentration found in region 4 was much higher than in the
242
other regions, indicating the potential for much more THMs formation in the estuarine
243
water than in inland river water.
244
Within the four types of THMs species (i.e., CHCl3, CHCl2Br, CHClBr2 and
245
CHBr3), chlorinated water samples from regions 1-3 produced relatively high
246
amounts of CHCl3. The next most abundant THM species in samples from these
247
regions was CHCl2Br levels, and only a small amount of CHBr3 (< 8%) was found in
248
them. Meanwhile chlorinated water samples from region 4 produced relatively high
249
amounts of CHBr3, followed by CHCl2Br. CHCl3 was minimally produced in these
250
samples (< 2%). This finding underscores the importance of Br− and Cl− levels in
251
determining the composition of DBPs (specifically, THMs) formed. In general, all the
252
samples produced CHCl3 and CHBr3 at levels that exceed the USEPA and EU limits
253
(Richardson et al., 2007).
254
Compared to chlorination, chloramine treatment generally resulted in lower total
255
concentrations of THMs. The average concentrations of THMs in the four regions
256
produced during chloramine treatment were 35.8, 35.0, 66.0, and 228.4 μg/L. The
257
molar concentrations were 0.19, 0.19, 0.33 and 0.96 μmol/L. For chloramine
258
treatment, only sampling site 23 and sampling sites within region 4 exceeded the
259
permissible levels recommended by the USEPA and EU limits (Richardson et al.,
ACCEPTED MANUSCRIPT 260
2007). Similar to our observation with chlorination treatment, water samples from
261
region 4 also showed higher levels of total THMs than those from region 1-3 upon
262
their treatment with chloramine. In contrast to chlorination however, CHCl3 was the
263
least abundant type of THMs (< 4%) when the water samples were chloraminated.
264
The most abundant species produced when the water samples were chloraminated was
265
CHCl2Br, followed by CHBr3 and CHClBr2 in samples 1-21, while CHBr3 was the
266
main species in samples 24-28.
267
Fig. 3 shows HAAs formed in the water samples from all sampling sites after
268
chlorination and chloramination. All HAAs, including monobromo-acetic acid
269
(MBAA), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), bromo-
270
chloroacetic acid (BCAA), dibromoacetic acid (DBAA), bromodichloroacetic acid
271
(BDCAA), chlorodibromoacetic acid (CDBAA) and bromoacetic acid (TBAA), were
272
detected after chlorination (Fig. 3a). The total levels of the HAAs (THAAs) detected
273
in waters from 22 of the 28 sampling sites exceeded USEPA regulatory limit of 60
274
μg/L for THAAs. The average concentrations of HAAs in the four regions formed
275
after chlorine treatment were 221.5, 188.0, 191.4, and 394.5 μg/L, respectively. The
276
molar concentrations were 1.42, 1.18, 1.15 and 1.59 μmol/L. Similar to the trend
277
observed in the spatial distribution of THMs and Br− levels, THAAs levels were
278
highest in region 4, but the difference was much lower than THMs. DCAA and
279
TCAA were the major species of HAAs detected in regions 1-3. In region 4 samples,
280
all the HAAs concentrations exceeded 250 g/L, with the highest being more than 600
281
g/L (detected in site 25). The dominant species formed with chlorination were
ACCEPTED MANUSCRIPT 282
DBAA and TBAA, which accounted for over 80% of the THAAs.
283
In this study, only five HAAs, including MBAA, DCAA, TCAA, BCAA, and
284
DBAA were detected when water samples were chloraminated (Fig. 3b), as other
285
HAAs were below the detection limit. THAAs formed from chloramination largely
286
decreased, compared to the amount formed with chlorination, to less than 30 g/L.
287
These findings show that disinfection with chloramine decreased the concentration
288
and speciation of HAAs formed. Diehl et al. (2000) showed that chloramination
289
mainly produces dihalogenated HAAs, while a mixture of mono-, di- and
290
trihalogenated HAAs are generated with chlorination.
291
Similar to our observation with chlorination, DCAA and TCAA were the major
292
HAAs species detected in regions 1-3, accounting for over 80% of the THAAs. These
293
findings agree with other studies (Malliarou et al., 2005). In contrast to our finding in
294
chlorinated water samples, THAAs detected in region 4 were not significantly higher
295
than those observed in regions 1-3 when disinfection was done via chloramination. As
296
such, the use of chloramine (instead of chlorine) as the disinfectant has a significant
297
impact on the speciation of HAAs (Goslan et al., 2009).
298
In addition to THMs and HAAs, which are regulated, the formation of other
299
DBPs by water samples collected from different parts of Haihe River was also
300
investigated. Fig. 4a-b shows the concentrations of HKs formed during chlorination
301
and chloramination. (Please note that while 1,1-dichloro-2-propanone (1,1-DCP) and
302
1,1,1-trichloro-2-propanone (1,1,1-TCP) were analyzed, their brominated analogs
303
were not analyzed due to lack of standards.) The levels of 1,1,1-TCP exceeded those
ACCEPTED MANUSCRIPT 304
of 1,1-DCP in all the water samples. When chlorination was applied, the highest 1,1-
305
DCP and 1,1,1-TCP concentrations detected were 7.51 and 17.9 μg/L respectively;
306
while the lowest concentrations found were 1.03 and 5.67 g/L, respectively. The
307
amounts of 1,1-DCP and 1,1,1-TCP formed with chloramination were much lower
308
than those from chlorination, mostly below 1 g/L. Surprisingly, the levels of HKs
309
detected in regions 1-3 were higher than those detected in region 4.
310
Two N-DBPs, HANs and TCNM, were measured in this study (Fig. 4c-d). Three
311
major
species
of
HANS,
which
are
dichloroacetonitrile
(DCAN),
312
bromochloroacetonitrile (BCAN), and dibromoacetonitrile (DBAN), were detected in
313
the water samples. The average levels of DCAN, BCAN and DBAN found in
314
chlorinated samples from sites 1 to 21 were 8.25, 4.75, and 2.98 μg/L, respectively.
315
These concentrations are higher or similar to the levels observed in a USEPA’s
316
occurrence survey, which had a median value of 3 g/L (Krasner et al., 2006). DBAN
317
was the most abundant species (~50-70%) in chlorine-treated water samples from
318
sites 22 to 28, probably due to higher bromide concentrations at these sites. The
319
highest concentration of DCAN (10.8 μg/L), BCAN (32.1 g/L), and DBAN (85.5
320
g/L) concentration was detected in water sample from site 4, site 24, site 25,
321
respectively, upon chlorination. DBAN was not detected when samples were
322
chloraminated (Fig. 4d), which shows the importance of the disinfecting agent
323
employed in the species and abundance of DBPs formed.
324
Amine and amino acids (such as methylamine, tyrosine and asparagine) are
325
typical precursors for TCNM upon water disinfection (Yang et al., 2012). TCNM
ACCEPTED MANUSCRIPT 326
generated during chlorination of water samples (which were generally ≤ 3 g/L) is
327
displayed in Fig. 4e. When water samples were treated with chloramine TCNM was
328
consistently below the detection limit. This is in agreement with a previous study
329
investigating the formation potential of HNMs from raw and treated waters with a
330
wide range of DOC and SUVA values, which found that chlorination generated more
331
TCNM than chloramination (Hu et al., 2010).
332 333
3.3. Effect of water characteristics on DBPs formation.
334
DBPs are formed from reactions between disinfectants and DOC present in water.
335
Therefore, the yield and species distribution of DBPs mainly depend on the type of
336
disinfectant employed and the characteristics of DOC. High DOC levels often result
337
in high DBPs levels but levels of DBPs, at times, cannot be directly correlated with
338
DOC levels. For instance, the large difference in THMs levels between chlorinated
339
water samples 23 and 28 cannot be explained by their similar DOC levels, suggesting
340
that other water chemistry factors (e.g. pH, Br− or Cl−) may also influence the
341
formation of DBPs.
342
Br− could be oxidized by HOCl (or aqueous Cl2) to form HOBr (Farkas, 1949),
343
which is much more reactive than HOCl (Vyak and Toroz, 2007; Symons et al.,
344
1993). Ichihashi et al. (1999) reported that the ratio of [NaOBr]/[NaOCl] determined
345
the speciation of brominated THMs generated from humic acid. Thus, high Br−
346
concentrations in region 4 tremendously influenced the speciation and abundance of
347
brominated DBPs detected in the water samples collected from that region.
ACCEPTED MANUSCRIPT 348
Furthermore, when chlorine is used as the disinfectant, two important equilibria occur
349
(Eq. 3 and 4):
350 351
HOCl ↔ OCl− + H+
Eq. 3
352
HOCl + Cl− + H+ ↔ Cl2 (aqueous) + H2O
Eq. 4
353 354
Increasing chloride concentration may further push the reaction toward aqueous
355
Cl2 formation, which is much more reactive with Br−, and can also lead to the
356
formation of Br-DBPs (Ichihashi et al., 1999). Thus the presence of high Br− and Cl−
357
concentrations may explain the high concentrations of some Br-DBPs observed in
358
region 4. Compared to other DBPs, HKs were not stable, and were decomposed to
359
THMs in the presence of relatively high concentrations of free chlorine (Nikolaou et
360
al., 2001), and thus, Cl−. In addition, high Br− levels may also contribute to the less
361
chlorinated HKs found in region 4.
362
To show the impact of bromide along the river, the bromine incorporation factor
363
(BIF) of halogenated THMs, HAAs and HANs were calculated according to the
364
definition of BIF (Hong et al., 2013) on a molar basis (Table 2). Levels of DBPs and
365
bromine used were average values determined in the individual region. BIF values of
366
the three groups of DBPs showed increasing trend with increasing of bromide levels,
367
which is similar with the previous reported results (Hong et al., 2013), suggesting the
368
pivotal role of Br− in determining the speciation of DBPs. BIF values of HAAs and
369
HANs were generally higher in chlorinated waters than in chloraminated waters.
ACCEPTED MANUSCRIPT 370
However, BIF values of THMs showed an opposite result, which indicated different
371
bromination capability of THMs compared with HAAs and HANs. Generally
372
speaking, amines are precursor of N-DBPs, and will directly affect the concentrations
373
of N-DBPs formed. Free amino acids, heterocyclic nitrogen in nucleic acids,
374
proteinaceous materials, and combined amino acids bound to humic structures are
375
important precursors of HANs (Wontae et al., 2007). High amine composition in
376
DOC may lead to high HANs production. NH3-N and NO2-N concentrations were not
377
much higher in region 4, compared to the other regions, to explain the relatively high
378
levels of HANs in the region. We thus hypothesize that higher concentrations of
379
HANs in region 4 is due to combined effects of high concentrations of NOM, Cl− and
380
Br−.
381 382
4. Conclusions
383
The formation and speciation of different kinds of DBPs during chlorination or
384
chloramination of water from Haihe River were studied. DBPs such as THMs, HAAs,
385
HANs, HKs and TCNM were found in water samples collected from 28 sites within
386
the river. Out of all the DBPs detected, THMs and HAAs were the most abundant
387
species, while the concentrations of HANs, HKs, and TCNM were much lower.
388
Compared to chlorine disinfection, much lower amounts of most of the DBPs were
389
formed by chloramination. In fact, BDCAA, CDBAA, TBAA, and TCNM were not
390
detected in water samples that were treated by chloramination. Due to the
391
considerable spatial difference in water composition in different parts of Haihe River,
ACCEPTED MANUSCRIPT 392
the concentrations and speciation distribution of DBPs observed in the different parts
393
of the river were quite different. The concentrations and composition of NOM is the
394
major factor for DBPs formation, but other water chemistry factors such as Cl− and
395
Br−, etc., also exert some influence.
396 397
ACCEPTED MANUSCRIPT 398
Acknowledgements
399
This research was supported by the National Basic Research Program of China
400
(2015CB459000), the National Natural Science Foundation of China (Project No.
401
21677078 and 21307060), the Tianjin Research Program of Application Foundation
402
and Advanced Technology (Project No. 13JCQNJC07900).
403
ACCEPTED MANUSCRIPT 404
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Fig. 1. Map showing the mainstream and tributaries of Haihe River. Numbers indicate the sampling sites in the Haihe River used in this study.
1
ACCEPTED MANUSCRIPT
1000
1000
a
600
CHClBr2 CHBr3
400
200
0
b
CHCl2Br
800
THM Conc. (g/L)
THM Conc. (g/L)
800
CHCl3
CHCl3 CHCl2Br CHClBr2 CHBr3
600
400
200
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Fig. 2. Concentrations of THMs formed in water samples from different parts of Haihe River formed during (a) chlorine-based disinfection, and (b) chloramine-based disinfection. ([Cl2], [NH2Cl] = 10 mg/L as Cl2, reaction time = 3 d, pH = 7).
2
ACCEPTED MANUSCRIPT
HAA Conc. (g/L)
600
100
a
500 400
MBAA DCAA TCAA BCAA DBAA BDCAA CDBAA TBAA
300 200
b 80 HAA Conc. (g/L)
700
60
40
20
100 0
MBAA DCAA TCAA BCAA TBAA
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Fig. 3. HAA concentrations in water samples from different sites formed during (a) chlorination, and (b) chloramination. ([Cl2], [NH2Cl] = 10 mg/L as Cl2, reaction time = 3 d, pH = 7)
3
ACCEPTED MANUSCRIPT
b
1,1-DCP 1,1,1-TCP
HKs Conc. (g/L)
30
20
10
0 140 120
HANs Conc. (g/L)
4
a
c
100
DCAN BCAN DBAN
80 60 40
1,1-DCP 1,1,1-TCP
3
2
1
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
60
HANs Conc. (g/L)
HKs Conc. (g/L)
40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
d
DCAN BCAN
40
20
20 0 3.0
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
e
TCNM Conc. (g/L)
2.5 2.0 1.5 1.0 .5 0.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Fig. 4. N-DBPs concentrations in water samples from different sites formed during (a) chlorination, and (b) chloramination. HANs in water samples from different sites formed during (c) chlorination, and (d) chloramination. (e) TCNM in water samples from different sites formed during chlorination. ([Cl2] [NH2Cl] = 10 mg/L as Cl2, reaction time = 3 d, pH = 7)
4
ACCEPTED MANUSCRIPT Table 1. Properties of samples collected from Haihe River Sample no.
DOC
UV254
SUVA
Br−
Cl−
NH3-N
NO2-N
(mg/L)
(cm-1)
(L/mg·m)
(mg/L)
(mg/L)
(g/L)
(mg/L)
1
8.71
0.12
1.33
0.06
20.18
0.94
0.17
2
6.31
0.12
1.87
0.04
20.15
1.02
0.05
3
7.23
0.12
1.63
0.06
20.4
0.64
0.31
4
5.77
0.13
2.17
0.05
24.34
1.2
0.11
5
6.1
0.14
2.25
0.2
79.5
1.63
0.09
6
5.72
0.13
2.24
0.16
55.12
0.86
0.03
7
9.62
0.12
1.26
0.17
69.42
0.75
0.01
8
6.41
0.12
1.92
0.15
55.08
0.67
0.05
average
6.98
0.13
1.83
0.11
43.02
0.96
0.10
9
5.7
0.12
2.07
0.18
60.34
0.58
0.06
10
5.63
0.12
2.17
0.17
56.82
1.01
0.09
11
5.17
0.12
2.28
0.15
55.86
1.14
0.13
12
5.31
0.12
2.24
0.17
56.54
1.02
0.11
13
5
0.12
2.42
0.14
53.02
0.68
0.07
14
6.05
0.12
1.97
0.16
53.26
0.53
0.07
15
11.93
0.12
1.02
0.17
55.78
1.05
0.07
16
6.16
0.12
1.98
0.18
71.04
0.73
0.08
17
5.89
0.12
2.01
0.15
60.48
0.8
0.05
18
5.82
0.13
2.15
0.21
71.5
0.89
0.09
average
6.27
0.12
2.03
0.17
59.46
0.84
0.08
19
10.69
0.13
1.25
0.2
83.2
0.85
0.09
20
7.18
0.13
1.84
0.18
76.16
0.88
0.12
21
14.57
0.15
1
0.4
158
2.39
0.07
22
6.88
0.16
2.3
0.61
254.82
1.55
0.23
23
10.43
0.17
1.64
0.13
53.25
1.78
0.03
average
9.95
0.15
1.61
0.30
125.09
1.49
0.11
24
8.01
0.23
2.92
0.99
321.37
1.98
0.22
25
10.14
0.18
1.73
2.76
6528.45
0.56
0.42
26
11.38
0.19
1.64
2.63
6157.96
1.15
0.4
27
10.74
0.18
1.65
2.51
6541.68
0.96
0.52
28
10.35
0.18
1.71
2.39
6529.18
0.94
0.52
average
10.12
0.19
1.93
2.26
5215.73
1.12
0.42
Table 2. Bromine incorporation factor (BIF) of DBPs as function of bromide level upon chlorination and chloramination. region
Br− (mg/L)
1
0.11
chlorination THMs 0.42
HAAs 0.32
chloramination HANs 0.48
THMs 1.52
HAAs 0.12
HANs 0.51
ACCEPTED MANUSCRIPT 2
0.17
0.40
0.36
0.50
1.53
0.12
0.51
3
0.30
0.73
0.52
0.77
1.77
0.24
0.69
4
2.26
2.26
2.64
1.48
2.69
1.13
0.96
Rongjie Hao, Yan Zhang, Tingting Du, Li Yang, Adeyemi S. Adeleye, Yao Li PII:
S0045-6535(16)31746-5
DOI:
10.1016/j.chemosphere.2016.12.034
Reference:
CHEM 18490
To appear in:
Chemosphere
Received Date:
28 August 2016
Revised Date:
05 December 2016
Accepted Date:
07 December 2016
Please cite this article as: Rongjie Hao, Yan Zhang, Tingting Du, Li Yang, Adeyemi S. Adeleye, Yao Li, Impact of water chemistry on disinfection by-products formation in the complex surface water system, Chemosphere (2016), doi: 10.1016/j.chemosphere.2016.12.034
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ACCEPTED MANUSCRIPT Highlights
High concentrations of DBPs were formed in the discharge Zone of Bohai Sea.
DBPs formation was highly affected by the combine water composition.
Br− and Cl− concentrations may highly affect the formation of Br-DBPs.
Compared to the chloramination, much more DBPs were formed with chlorination disinfection.
ACCEPTED MANUSCRIPT
1
Impact of water chemistry on disinfection by-products
2
formation in the complex surface water system
3 4
Rongjie Hao,1 Yan Zhang,1 Tingting Du,1 Li Yang,1 Adeyemi S. Adeleye,2 Yao Li1*
5 6
1 College of Environmental Science and Engineering/Ministry of Education Key Laboratory of
7
Pollution Processes and Environmental Criteria/Tianjin Key Laboratory of Environmental
8
Remediation and Pollution Control, Nankai University, Tong Yan Road 38, Tianjin 300350, China
9
2 Bren School of Environmental Science and Management, University of California, Santa
10
Barbara, California 93106, United States
11 12 13 14
*To whom correspondence may be addressed: (Phone/fax) 86-22-2350-1117; (e-mail)
15
[email protected].
16 17
ACCEPTED MANUSCRIPT 18
Abstract
19
The relationship between the disinfection by-products (DBPs) formed with
20
chlorination and chloramination techniques, and the water chemistry of Haihe River
21
was compared. Samples were collected at 28 different points within the mainstream
22
and tributaries of the river. The DBPs investigated include trihalomethanes (THMs),
23
haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones (HKs) and
24
trichloronitromethane (TCNM). THMs formed when samples were chlorinated mostly
25
exceeded 100 μg/L and 600 μg/L in the mainstream, tributaries and in the estuary,
26
respectively. A similar trend was obtained for HAAs whose concentrations exceeded
27
150 μg/L in almost all samples. The amounts of DBPs formed when samples were
28
chloraminated were much lower than when chlorination was employed. The
29
concentrations and species of THMs and HAAs in samples collected from sites
30
nearby the estuary were different from those in samples collected from the
31
mainstream, which may be due to high concentrations of Cl− and Br−. Although
32
natural organic matter (NOM) is the major cause of DBPs formation during water
33
disinfection, this study shows that other water chemistry factors, such as salt
34
composition and concentrations, may also significantly affect the formation of DBPs
35
in natural aquatic systems.
36 37
Keywords：disinfection by-products, chlorination and chloramination, surface
38
water, water chemistry
39
ACCEPTED MANUSCRIPT 40
1. Introduction
41
Disinfection has long been widely used to kill different pathogens in drinking
42
water. However, it is also responsible for the formation of disinfection by-products
43
(DBPs), which may have serious negative effects on human health (Zhang et al.,
44
2000; Richardson et al., 2003; Krasner et al., 2006). DBPs were first described in
45
1974 (Rook, 1974), and have been studied for more than 40 years. Several studies
46
have investigated the different types of DBPs—known and unknown— that may form
47
in natural waters, and their effects to humans. Trihalomethanes (THMs) and
48
haloacetic acids (HAAs), two most prevalent priority DBPs found in chlorinated
49
drinking water worldwide (Zeng, et al., 2016), are typically used as the proxies for
50
estimating DBPs amounts (Krasner and Aieta, 1989; Pontius, 1993). Meanwhile,
51
during disinfection with chloramine, some organic chloramines (N-DBPs) are formed
52
(Westerhoff and Mash, 2002; Yang and Shang, 2004), which were shown to be more
53
toxic than THMs and HAAs. A new series of brominated and iodinated anilines were
54
recently identified, which may also improve the cognition of DBPs and their effect on
55
human being (Zhang et al., 2008; Ding and Zhang, 2009; Li et al., 2010, 2011).
56
The formation of all these traditional and/or new DBPs in natural systems may
57
be greatly affected by water chemistry and compositions. Water components such as
58
natural organic materials (NOMs), chlorides and bromides, salts, and N-containing
59
compounds, are present at different levels in many sources of drinking water, and they
60
can significantly affect the formation of DBPs (Kim and Yu, 2005; Bougeard et al.,
61
2010). For example, since the NOM is the precursor of DBPs, the composition and
ACCEPTED MANUSCRIPT 62
the amount of NOM present determines the species and quantity of DBPs that will
63
form (Fang et al., 2010; Richardson et al., 2003). In addition, bromide in the water
64
may promote the formation of brominated DBPs (Zhai et al., 2011, 2014). Salts may
65
not directly cause the formation of DBPs, but they affect the concentrations and type
66
of DBPs formed in saline water systems (Pan et al., 2016). The individual effects of
67
each of these factors (salts, NOM, etc.) on the formation of DBPs have been
68
comprehensively studied (Chellam, 2000; Bolto et al., 2004; Sharp et al., 2006;
69
Matilainen et al., 2010), but the impact of the different factors in the complex water
70
systems remains unclear and needs to be investigated.
71
Haihe River, which is located in Tianjin, an essential industrial and high-tech
72
production city of China, is one of the largest rivers in northern China and it
73
discharges into the Bohai Sea. The river receives high inputs of domestic, industrial
74
and agricultural wastewater (Jin et al., 2004), and consists of a mainstream and many
75
tributaries, such as Ziya river, Xinkai river, the Beiyun river, the Nanyun river,
76
Fuxing River, and so on (Yang et al., 2005). Haihe River covers a distance of 1090
77
km around zones of different land-uses; and with so many tributaries, its chemistry
78
and composition (such as NOM concentrations, salts, and N-containing materials) at
79
different points vary widely. In particular, formation of new DBPs have been
80
observed in its tributaries, which makes it an ideal natural system for DBPs formation
81
studies (Yang and Zhang, 2013, 2014; Liu and Zhang, 2014). The possible input of
82
disinfectant into river with wastewater cannot be ignored. Besides, though some
83
saline locations on the Haihe were not suitable as a drinking water supply right now,
ACCEPTED MANUSCRIPT 84
the suitability of Haihe River as drinking water source in the future also need to be
85
evaluated due to growing demand for water in Northern China (The use of Haihe
86
River as a drinking water source was discontinued decades ago due to pollution.).
87
The major objective of this study was to investigate DBPs formation at different
88
points in Haihe River and to correlate DBPs formation with the properties of water in
89
a holistic manner. In this study Haihe River was divided into four distinct regions
90
based on the sampling positions and water chemistry. All DBPs, including THMs,
91
HAAs, haloacetonitriles (HANs), haloketones (HKs), and trichloronitromethane
92
(TCNM) were measured, and compared between two main disinfection methods—
93
chlorination and chloramination. The effects of water composition on DBPs formation
94
were also investigated within the different regions. In order to obtain a more obvious
95
comparison of the results in a short period of time, we have adopted higher amount of
96
disinfectant than that of the conventional dosage in the experimental procedures and
97
have not conducted DOC removal process.
98 99 100
Materials and methods 2.1. Sample collection and analyses
101
A total of 28 water samples were collected from Haihe River. There were 15
102
sampling sites in the mainstream, and 13 sampling sites in the eight tributaries. The
103
sampling sites locations are shown in Fig. 1.
104
Samples 1-8 were collected from the four tributaries upstream in Tianjin.
105
Samples 9-24 were collected around the mid-point of the main river, except samples
ACCEPTED MANUSCRIPT 106
15, 19, 21-23, which were from the surrounding tributaries around the mid-point.
107
Samples 25-28 were collected downstream around the point of discharge into the sea,
108
which is an estuary due to mixing with seawater. Based on the sampling position and
109
chemical composition, the entire sampling sites were broadly divided into four
110
regions: Region 1 consisted of samples 1-8, representing the samples collected from
111
upstream tributaries; Region 2 was made up of samples 9-18, representing the
112
samples mainly collected from the upper- and mid- mainstream (sample site 15 was
113
very close to the mainstream); Region 3 consisted of samples 19-23, which represents
114
samples collected mostly from the mid-stream tributaries; and region 4, consisting of
115
samples 24-28, representing the samples collected around the discharge zone of the
116
river into the Bohai Sea (Based on water composition, sample 24 was classified into
117
this region.). The chemical composition of region 4 is mainly affected by seawater
118
reflux, and regions 1-3 are mainly freshwaters.
119
After collection, samples were shipped to the laboratory and kept at 4 ◦C until the
120
samples were analyzed, which was less than 24 hours. Prior to analyses, all the
121
samples were filtered with a 0.45 µm membrane to eliminate particulate and
122
biological contaminants. The chlorinated/chloraminated filtered DI blank controls
123
were evaluated and no significant DBPs precursors were detected. After that,
124
dissolved organic carbon (DOC) concentration, UV absorbance at 254 nm (UV254),
125
bromide ion concentration, chloride ion concentration, NH3-N concentration, and
126
NO2-N concentration were determined. Specific UV absorbance (SUVA) was
127
calculated as UV254 divided by DOC.
ACCEPTED MANUSCRIPT 128 129
2.2. Chemicals and materials
130
Working solutions were prepared from reagent grade chemicals or stock
131
solutions. Dilution to target aqueous-phase concentrations was accomplished with
132
Milli-Q water. Stock of sodium hypochlorite (NaClO), which was purchased from
133
Sigma-Aldrich Corporation, was diluted to 900-1000 mg/L (as Cl2), stored in
134
aluminum foil-covered bottle, and kept at 4 ◦C until use. The stock solution was
135
periodically titrated by DPD/FAS titration before each experiment (APHA et al.,
136
1998). Monochloramine (NH2Cl) solution was prepared daily prior to experiments by
137
quickly adding equal volumes of ammonium chloride and sodium hypochlorite
138
solutions at a weight ratio of 4 mg/L Cl2 to 1 mg/L N-NH4+ with rapid stirring for 30
139
min (Yang et al., 2007). The solutions were then standardized by DPD/FAS titration
140
(APHA et al., 1998). All the DBP standards, including a mixture standard containing
141
THMs, HANs, HKs, and TCNM; a mixed standard of nine HAAs; and surrogate
142
standards were obtained from Sigma-Aldrich (Supelco, USA). Methyl–tert butyl ether
143
(MtBE) was obtained from AMP (Shanghai, China).
144 145
2.3. Experimental procedures
146
All the experiments (chlorination/chloramination) were carried out in 60 mL
147
amber-colored bottles. The dosage of chlorine (Cl2) was determined by the formula
148
approach shown in equation 1 (Krasner et al., 2008, 2009):
149
ACCEPTED MANUSCRIPT 150 151
Cl2 (mg/L)= 3*[mg/L dissolved organic carbon (DOC)] + 8*[mg/L NH3-N] +5*[mg/L NO2 -N] + 10 mg/L
Eq. 1
152 153 154
In chloramination tests, the dosage of monochloramine (NH2Cl) was determined by the formula shown in equation 2:
155 156
NH2Cl (mg/L) = 3*[mg/L DOC] + 5*[mg/L NO2-N]
Eq. 2
157 158
10 mM phosphate buffer was added into the samples to adjust the pH to 7, and all
159
samples were incubated in the dark at room temperature (25 ± 1 ◦C) for 3 d. After
160
incubation, reactions were quenched by adding ascorbic acid, and sample extraction
161
was immediately carried out with MtBE, as extractant and anhydrous sodium sulfate
162
as drying agent based on the liquid–liquid extraction process (Du et al., 2016). The
163
extracts were then analyzed via gas chromatography. All experimental conditions are
164
based on the formation potential test, and no water treatment was done to the Haihe
165
revier before the DBPs detection.
166 167
2.4. Analytical methods
168
Total organic carbon (TOC) concentrations were measured using a total organic
169
carbon analyzer (multi N/C 3100, Germany). UV254 was measured using a UV–visible
170
spectrophotometer (Shimadzu Scientific Instruments, USA). Cl− and Br− were
171
measured using an ion chromatograph (ICS1600, Thermo Fisher Scientific, USA).
ACCEPTED MANUSCRIPT 172
NH3-N concentrations were measured by Nessler’s reagent spectrophotometry (GB
173
7479-87), and NO2-N concentrations were measured by Spectrophotometric method
174
(GB 749-87). THMs, HKs and N-DBPs (HANs and TCNM) were analyzed via gas
175
chromatography (Agilent 6890N, Santa Clara, CA) connected to an electron capture
176
detector (GC-ECD) (Agilent Technologies, Santa Clara, CA) using USEPA Method
177
551.1. The column used was a HP-5 fused silica capillary column (30 mm×0.25 mm
178
I.D. with 0.25 μm film thickness, J&W Scientific, USA). The GC temperature
179
program consisted of an initial temperature of 35 °C for 6 min, ramped to 100 °C at
180
10 °C/min and held for 5 min, and finally, ramped to 200 °C at 20 °C/min and held
181
for 2 min. HAAs were also analyzed using the GC-ECD based on USEPA Method
182
552.2. The GC temperature program for HAAs analyses consisted of an initial
183
temperature of 35 °C for 10 min, ramped to 60 °C at 5°C/min, ramped to 75 °C at 2
184
°C/min and held for 2 min, ramped to 135 °C at 20 °C/min, and then ramped to 200
185
°C at 5 °C/min and held for 5 min.
186 187
3. Results and discussions
188
3.1. Water characteristic
189
The water properties at the 28 sampling points were summarized in Table 1. As
190
the primary DBPs precursor in aqueous systems, DOC is important for DBPs
191
formation. The DOC concentrations detected in regions 1-3 (i.e. upstream and mid-
192
stream sampling sites) ranged from 5.0 mg/L to 14.6 mg/L, and rank among the
193
highest DOC levels reported for Chinese inland waters (Gu et al., 2010; Hong et al.,
ACCEPTED MANUSCRIPT 194
2013, 2015). As can been seen in Table 1, DOC was particularly high in mid-stream
195
tributaries 15, 19, 21 and 23, which is primarily due to nearby contamination sources
196
such as wastewater treatment plant, hoggery and fish farms. Interestingly, the highest
197
average DOC (10.12 mg/L) was determined in region 4, around the delta of Bohai
198
Sea.
199
UV254 values obtained in this study were also relatively high compared to those
200
previously reported for Chinese key river systems (Wang et al., 2013). In general, the
201
average UV254 values increased downstream towards the Bohai bay. The highest value
202
0.23 cm-1 was found in sampling site 24. It should be noted that the correlation
203
between DOC and UV254 was not strong, which indicates the presence of different
204
types of NOM contents in different parts of the water. The spatial distribution of
205
SUVA was quite different from that of DOC and UV254. A high SUVA value (≥
206
4 L/mg·m) means a relatively high content of hydrophobic organic compounds, while
207
a low SUVA (≤ 3 L/mg·m) suggests a high percentage of hydrophilic organic
208
compounds (Zheng, 2016). The range of SUVA values obtained from the water
209
samples (1-2.92 L/mg·m) suggests the dominance of hydrophilic NOM types in Haihe
210
River.
211
Cl− and Br− levels in Haihe River increased with proximity to the Bohai Bay,
212
with a range of 20.2 mg/L to 6541.7 mg/L and 0.04 mg/L to 2.76 mg/L, respectively.
213
Sampling site 22, which was located at Laohai River, an old waterway of Haihe
214
River, had abnormally high Cl− concentration (254.8 mg/L) compared to the range
215
detected in the sample collected from neighboring waters (53.3-158 mg/L). NH3-N
ACCEPTED MANUSCRIPT 216
concentrations in more than 40% of the sampling sites were higher than 1 mg/L, the
217
Chinese surface water standard Ⅲ level. The highest NH3-N concentration (2.39
218
mg/L) was detected in Yueya River, which is higher than the Chinese surface water
219
standard Ⅴ level (2 mg/L). The high level of NH3-N is probably due to waste stream
220
discharges from the frozen food factory located around the waterbody. The highest
221
levels of NO2-N were detected in samples from Ziya River (an upstream tributary),
222
(Laohai River) (a mid-stream tributary) and all the samples from region 4 (the estuary
223
zone). All these variations in water properties are expected to play an important role
224
in the amount and types of DBPs that will be formed upon chlorination and
225
chloramination of water samples.
226 227
3.2. DBPs formation in Haihe River.
228
Five DBP types, including THMs, HAAs, HANs, HKs, and TCNM were
229
detected in all samples; and most of them could be detected with both chlorine and
230
chloramine disinfection procedures. The concentrations of individual THMs,
231
including CHCl3, CHCl2Br, CHClBr2 and CHBr3, and total THMs (TTHMs) are
232
shown in Fig. 2. THMs were detected in all the samples upon chlorination (Fig. 2a).
233
The concentrations of the THMs detected exceeded the maximum amount found in
234
typical water treatment plants in China (Ye, et al., 2009); and mostly exceeded the EU
235
and USEPA limits (80 μg/L and 100 μg/L, respectively) (Richardson et al., 2007). As
236
the DOC precursors were not removed with water treatment processes before the
237
DBPs test, the DBPs formation in this study can only reflect the DBPs formation
ACCEPTED MANUSCRIPT 238
potential in the Haihe river and the impact of water chemistry on the DBPs formation.
239
The average concentrations of THMs in the four regions were 144.3, 148.8, 128.9,
240
and 721.3 μg/L, respectively. The molar concentrations were 1.12, 1.17, 0.90 and 3.00
241
μmol/L. The TTHMs concentration found in region 4 was much higher than in the
242
other regions, indicating the potential for much more THMs formation in the estuarine
243
water than in inland river water.
244
Within the four types of THMs species (i.e., CHCl3, CHCl2Br, CHClBr2 and
245
CHBr3), chlorinated water samples from regions 1-3 produced relatively high
246
amounts of CHCl3. The next most abundant THM species in samples from these
247
regions was CHCl2Br levels, and only a small amount of CHBr3 (< 8%) was found in
248
them. Meanwhile chlorinated water samples from region 4 produced relatively high
249
amounts of CHBr3, followed by CHCl2Br. CHCl3 was minimally produced in these
250
samples (< 2%). This finding underscores the importance of Br− and Cl− levels in
251
determining the composition of DBPs (specifically, THMs) formed. In general, all the
252
samples produced CHCl3 and CHBr3 at levels that exceed the USEPA and EU limits
253
(Richardson et al., 2007).
254
Compared to chlorination, chloramine treatment generally resulted in lower total
255
concentrations of THMs. The average concentrations of THMs in the four regions
256
produced during chloramine treatment were 35.8, 35.0, 66.0, and 228.4 μg/L. The
257
molar concentrations were 0.19, 0.19, 0.33 and 0.96 μmol/L. For chloramine
258
treatment, only sampling site 23 and sampling sites within region 4 exceeded the
259
permissible levels recommended by the USEPA and EU limits (Richardson et al.,
ACCEPTED MANUSCRIPT 260
2007). Similar to our observation with chlorination treatment, water samples from
261
region 4 also showed higher levels of total THMs than those from region 1-3 upon
262
their treatment with chloramine. In contrast to chlorination however, CHCl3 was the
263
least abundant type of THMs (< 4%) when the water samples were chloraminated.
264
The most abundant species produced when the water samples were chloraminated was
265
CHCl2Br, followed by CHBr3 and CHClBr2 in samples 1-21, while CHBr3 was the
266
main species in samples 24-28.
267
Fig. 3 shows HAAs formed in the water samples from all sampling sites after
268
chlorination and chloramination. All HAAs, including monobromo-acetic acid
269
(MBAA), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), bromo-
270
chloroacetic acid (BCAA), dibromoacetic acid (DBAA), bromodichloroacetic acid
271
(BDCAA), chlorodibromoacetic acid (CDBAA) and bromoacetic acid (TBAA), were
272
detected after chlorination (Fig. 3a). The total levels of the HAAs (THAAs) detected
273
in waters from 22 of the 28 sampling sites exceeded USEPA regulatory limit of 60
274
μg/L for THAAs. The average concentrations of HAAs in the four regions formed
275
after chlorine treatment were 221.5, 188.0, 191.4, and 394.5 μg/L, respectively. The
276
molar concentrations were 1.42, 1.18, 1.15 and 1.59 μmol/L. Similar to the trend
277
observed in the spatial distribution of THMs and Br− levels, THAAs levels were
278
highest in region 4, but the difference was much lower than THMs. DCAA and
279
TCAA were the major species of HAAs detected in regions 1-3. In region 4 samples,
280
all the HAAs concentrations exceeded 250 g/L, with the highest being more than 600
281
g/L (detected in site 25). The dominant species formed with chlorination were
ACCEPTED MANUSCRIPT 282
DBAA and TBAA, which accounted for over 80% of the THAAs.
283
In this study, only five HAAs, including MBAA, DCAA, TCAA, BCAA, and
284
DBAA were detected when water samples were chloraminated (Fig. 3b), as other
285
HAAs were below the detection limit. THAAs formed from chloramination largely
286
decreased, compared to the amount formed with chlorination, to less than 30 g/L.
287
These findings show that disinfection with chloramine decreased the concentration
288
and speciation of HAAs formed. Diehl et al. (2000) showed that chloramination
289
mainly produces dihalogenated HAAs, while a mixture of mono-, di- and
290
trihalogenated HAAs are generated with chlorination.
291
Similar to our observation with chlorination, DCAA and TCAA were the major
292
HAAs species detected in regions 1-3, accounting for over 80% of the THAAs. These
293
findings agree with other studies (Malliarou et al., 2005). In contrast to our finding in
294
chlorinated water samples, THAAs detected in region 4 were not significantly higher
295
than those observed in regions 1-3 when disinfection was done via chloramination. As
296
such, the use of chloramine (instead of chlorine) as the disinfectant has a significant
297
impact on the speciation of HAAs (Goslan et al., 2009).
298
In addition to THMs and HAAs, which are regulated, the formation of other
299
DBPs by water samples collected from different parts of Haihe River was also
300
investigated. Fig. 4a-b shows the concentrations of HKs formed during chlorination
301
and chloramination. (Please note that while 1,1-dichloro-2-propanone (1,1-DCP) and
302
1,1,1-trichloro-2-propanone (1,1,1-TCP) were analyzed, their brominated analogs
303
were not analyzed due to lack of standards.) The levels of 1,1,1-TCP exceeded those
ACCEPTED MANUSCRIPT 304
of 1,1-DCP in all the water samples. When chlorination was applied, the highest 1,1-
305
DCP and 1,1,1-TCP concentrations detected were 7.51 and 17.9 μg/L respectively;
306
while the lowest concentrations found were 1.03 and 5.67 g/L, respectively. The
307
amounts of 1,1-DCP and 1,1,1-TCP formed with chloramination were much lower
308
than those from chlorination, mostly below 1 g/L. Surprisingly, the levels of HKs
309
detected in regions 1-3 were higher than those detected in region 4.
310
Two N-DBPs, HANs and TCNM, were measured in this study (Fig. 4c-d). Three
311
major
species
of
HANS,
which
are
dichloroacetonitrile
(DCAN),
312
bromochloroacetonitrile (BCAN), and dibromoacetonitrile (DBAN), were detected in
313
the water samples. The average levels of DCAN, BCAN and DBAN found in
314
chlorinated samples from sites 1 to 21 were 8.25, 4.75, and 2.98 μg/L, respectively.
315
These concentrations are higher or similar to the levels observed in a USEPA’s
316
occurrence survey, which had a median value of 3 g/L (Krasner et al., 2006). DBAN
317
was the most abundant species (~50-70%) in chlorine-treated water samples from
318
sites 22 to 28, probably due to higher bromide concentrations at these sites. The
319
highest concentration of DCAN (10.8 μg/L), BCAN (32.1 g/L), and DBAN (85.5
320
g/L) concentration was detected in water sample from site 4, site 24, site 25,
321
respectively, upon chlorination. DBAN was not detected when samples were
322
chloraminated (Fig. 4d), which shows the importance of the disinfecting agent
323
employed in the species and abundance of DBPs formed.
324
Amine and amino acids (such as methylamine, tyrosine and asparagine) are
325
typical precursors for TCNM upon water disinfection (Yang et al., 2012). TCNM
ACCEPTED MANUSCRIPT 326
generated during chlorination of water samples (which were generally ≤ 3 g/L) is
327
displayed in Fig. 4e. When water samples were treated with chloramine TCNM was
328
consistently below the detection limit. This is in agreement with a previous study
329
investigating the formation potential of HNMs from raw and treated waters with a
330
wide range of DOC and SUVA values, which found that chlorination generated more
331
TCNM than chloramination (Hu et al., 2010).
332 333
3.3. Effect of water characteristics on DBPs formation.
334
DBPs are formed from reactions between disinfectants and DOC present in water.
335
Therefore, the yield and species distribution of DBPs mainly depend on the type of
336
disinfectant employed and the characteristics of DOC. High DOC levels often result
337
in high DBPs levels but levels of DBPs, at times, cannot be directly correlated with
338
DOC levels. For instance, the large difference in THMs levels between chlorinated
339
water samples 23 and 28 cannot be explained by their similar DOC levels, suggesting
340
that other water chemistry factors (e.g. pH, Br− or Cl−) may also influence the
341
formation of DBPs.
342
Br− could be oxidized by HOCl (or aqueous Cl2) to form HOBr (Farkas, 1949),
343
which is much more reactive than HOCl (Vyak and Toroz, 2007; Symons et al.,
344
1993). Ichihashi et al. (1999) reported that the ratio of [NaOBr]/[NaOCl] determined
345
the speciation of brominated THMs generated from humic acid. Thus, high Br−
346
concentrations in region 4 tremendously influenced the speciation and abundance of
347
brominated DBPs detected in the water samples collected from that region.
ACCEPTED MANUSCRIPT 348
Furthermore, when chlorine is used as the disinfectant, two important equilibria occur
349
(Eq. 3 and 4):
350 351
HOCl ↔ OCl− + H+
Eq. 3
352
HOCl + Cl− + H+ ↔ Cl2 (aqueous) + H2O
Eq. 4
353 354
Increasing chloride concentration may further push the reaction toward aqueous
355
Cl2 formation, which is much more reactive with Br−, and can also lead to the
356
formation of Br-DBPs (Ichihashi et al., 1999). Thus the presence of high Br− and Cl−
357
concentrations may explain the high concentrations of some Br-DBPs observed in
358
region 4. Compared to other DBPs, HKs were not stable, and were decomposed to
359
THMs in the presence of relatively high concentrations of free chlorine (Nikolaou et
360
al., 2001), and thus, Cl−. In addition, high Br− levels may also contribute to the less
361
chlorinated HKs found in region 4.
362
To show the impact of bromide along the river, the bromine incorporation factor
363
(BIF) of halogenated THMs, HAAs and HANs were calculated according to the
364
definition of BIF (Hong et al., 2013) on a molar basis (Table 2). Levels of DBPs and
365
bromine used were average values determined in the individual region. BIF values of
366
the three groups of DBPs showed increasing trend with increasing of bromide levels,
367
which is similar with the previous reported results (Hong et al., 2013), suggesting the
368
pivotal role of Br− in determining the speciation of DBPs. BIF values of HAAs and
369
HANs were generally higher in chlorinated waters than in chloraminated waters.
ACCEPTED MANUSCRIPT 370
However, BIF values of THMs showed an opposite result, which indicated different
371
bromination capability of THMs compared with HAAs and HANs. Generally
372
speaking, amines are precursor of N-DBPs, and will directly affect the concentrations
373
of N-DBPs formed. Free amino acids, heterocyclic nitrogen in nucleic acids,
374
proteinaceous materials, and combined amino acids bound to humic structures are
375
important precursors of HANs (Wontae et al., 2007). High amine composition in
376
DOC may lead to high HANs production. NH3-N and NO2-N concentrations were not
377
much higher in region 4, compared to the other regions, to explain the relatively high
378
levels of HANs in the region. We thus hypothesize that higher concentrations of
379
HANs in region 4 is due to combined effects of high concentrations of NOM, Cl− and
380
Br−.
381 382
4. Conclusions
383
The formation and speciation of different kinds of DBPs during chlorination or
384
chloramination of water from Haihe River were studied. DBPs such as THMs, HAAs,
385
HANs, HKs and TCNM were found in water samples collected from 28 sites within
386
the river. Out of all the DBPs detected, THMs and HAAs were the most abundant
387
species, while the concentrations of HANs, HKs, and TCNM were much lower.
388
Compared to chlorine disinfection, much lower amounts of most of the DBPs were
389
formed by chloramination. In fact, BDCAA, CDBAA, TBAA, and TCNM were not
390
detected in water samples that were treated by chloramination. Due to the
391
considerable spatial difference in water composition in different parts of Haihe River,
ACCEPTED MANUSCRIPT 392
the concentrations and speciation distribution of DBPs observed in the different parts
393
of the river were quite different. The concentrations and composition of NOM is the
394
major factor for DBPs formation, but other water chemistry factors such as Cl− and
395
Br−, etc., also exert some influence.
396 397
ACCEPTED MANUSCRIPT 398
Acknowledgements
399
This research was supported by the National Basic Research Program of China
400
(2015CB459000), the National Natural Science Foundation of China (Project No.
401
21677078 and 21307060), the Tianjin Research Program of Application Foundation
402
and Advanced Technology (Project No. 13JCQNJC07900).
403
ACCEPTED MANUSCRIPT 404
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Fig. 1. Map showing the mainstream and tributaries of Haihe River. Numbers indicate the sampling sites in the Haihe River used in this study.
1
ACCEPTED MANUSCRIPT
1000
1000
a
600
CHClBr2 CHBr3
400
200
0
b
CHCl2Br
800
THM Conc. (g/L)
THM Conc. (g/L)
800
CHCl3
CHCl3 CHCl2Br CHClBr2 CHBr3
600
400
200
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Fig. 2. Concentrations of THMs formed in water samples from different parts of Haihe River formed during (a) chlorine-based disinfection, and (b) chloramine-based disinfection. ([Cl2], [NH2Cl] = 10 mg/L as Cl2, reaction time = 3 d, pH = 7).
2
ACCEPTED MANUSCRIPT
HAA Conc. (g/L)
600
100
a
500 400
MBAA DCAA TCAA BCAA DBAA BDCAA CDBAA TBAA
300 200
b 80 HAA Conc. (g/L)
700
60
40
20
100 0
MBAA DCAA TCAA BCAA TBAA
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Fig. 3. HAA concentrations in water samples from different sites formed during (a) chlorination, and (b) chloramination. ([Cl2], [NH2Cl] = 10 mg/L as Cl2, reaction time = 3 d, pH = 7)
3
ACCEPTED MANUSCRIPT
b
1,1-DCP 1,1,1-TCP
HKs Conc. (g/L)
30
20
10
0 140 120
HANs Conc. (g/L)
4
a
c
100
DCAN BCAN DBAN
80 60 40
1,1-DCP 1,1,1-TCP
3
2
1
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
60
HANs Conc. (g/L)
HKs Conc. (g/L)
40
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
d
DCAN BCAN
40
20
20 0 3.0
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
e
TCNM Conc. (g/L)
2.5 2.0 1.5 1.0 .5 0.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
Fig. 4. N-DBPs concentrations in water samples from different sites formed during (a) chlorination, and (b) chloramination. HANs in water samples from different sites formed during (c) chlorination, and (d) chloramination. (e) TCNM in water samples from different sites formed during chlorination. ([Cl2] [NH2Cl] = 10 mg/L as Cl2, reaction time = 3 d, pH = 7)
4
ACCEPTED MANUSCRIPT Table 1. Properties of samples collected from Haihe River Sample no.
DOC
UV254
SUVA
Br−
Cl−
NH3-N
NO2-N
(mg/L)
(cm-1)
(L/mg·m)
(mg/L)
(mg/L)
(g/L)
(mg/L)
1
8.71
0.12
1.33
0.06
20.18
0.94
0.17
2
6.31
0.12
1.87
0.04
20.15
1.02
0.05
3
7.23
0.12
1.63
0.06
20.4
0.64
0.31
4
5.77
0.13
2.17
0.05
24.34
1.2
0.11
5
6.1
0.14
2.25
0.2
79.5
1.63
0.09
6
5.72
0.13
2.24
0.16
55.12
0.86
0.03
7
9.62
0.12
1.26
0.17
69.42
0.75
0.01
8
6.41
0.12
1.92
0.15
55.08
0.67
0.05
average
6.98
0.13
1.83
0.11
43.02
0.96
0.10
9
5.7
0.12
2.07
0.18
60.34
0.58
0.06
10
5.63
0.12
2.17
0.17
56.82
1.01
0.09
11
5.17
0.12
2.28
0.15
55.86
1.14
0.13
12
5.31
0.12
2.24
0.17
56.54
1.02
0.11
13
5
0.12
2.42
0.14
53.02
0.68
0.07
14
6.05
0.12
1.97
0.16
53.26
0.53
0.07
15
11.93
0.12
1.02
0.17
55.78
1.05
0.07
16
6.16
0.12
1.98
0.18
71.04
0.73
0.08
17
5.89
0.12
2.01
0.15
60.48
0.8
0.05
18
5.82
0.13
2.15
0.21
71.5
0.89
0.09
average
6.27
0.12
2.03
0.17
59.46
0.84
0.08
19
10.69
0.13
1.25
0.2
83.2
0.85
0.09
20
7.18
0.13
1.84
0.18
76.16
0.88
0.12
21
14.57
0.15
1
0.4
158
2.39
0.07
22
6.88
0.16
2.3
0.61
254.82
1.55
0.23
23
10.43
0.17
1.64
0.13
53.25
1.78
0.03
average
9.95
0.15
1.61
0.30
125.09
1.49
0.11
24
8.01
0.23
2.92
0.99
321.37
1.98
0.22
25
10.14
0.18
1.73
2.76
6528.45
0.56
0.42
26
11.38
0.19
1.64
2.63
6157.96
1.15
0.4
27
10.74
0.18
1.65
2.51
6541.68
0.96
0.52
28
10.35
0.18
1.71
2.39
6529.18
0.94
0.52
average
10.12
0.19
1.93
2.26
5215.73
1.12
0.42
Table 2. Bromine incorporation factor (BIF) of DBPs as function of bromide level upon chlorination and chloramination. region
Br− (mg/L)
1
0.11
chlorination THMs 0.42
HAAs 0.32
chloramination HANs 0.48
THMs 1.52
HAAs 0.12
HANs 0.51
ACCEPTED MANUSCRIPT 2
0.17
0.40
0.36
0.50
1.53
0.12
0.51
3
0.30
0.73
0.52
0.77
1.77
0.24
0.69
4
2.26
2.26
2.64
1.48
2.69
1.13
0.96