Chemosphere 117 (2014) 515–520

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Chemosphere

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Effects of ozonation on disinfection byproduct formation and speciationduring subsequent chlorination

http://dx.doi.org/10.1016/j.chemosphere.2014.08.0830045-6535/� 2014 Published by Elsevier Ltd.

⇑ Corresponding author.

Yuqin Mao a, Xiaomao Wang a, Hongwei Yang a,⇑, Haoyu Wang a, Yuefeng F. Xie a,b

a State Key Joint Laboratory of Environmental Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, Chinab Environmental Engineering Programs, The Pennsylvania State University, Middletown, PA 17057, USA

h i g h l i g h t s

� Ozonation alone did not generate significant amount of brominated DBPs.� Ozonation prior to chlorination might increase the formation potential of many DBP classes.� THM, THAA, and DHAA formation potentials first increased and then decreased with increased ozone dose.� Ozonation prior to chlorination caused a shift to more brominated DBPs.

a r t i c l e i n f o

Article history:Received 13 March 2014Received in revised form 26 August 2014Accepted 27 August 2014Available online 29 September 2014

Handling Editor: O. Hao

Keywords:OzoneDisinfection by-products (DBPs)Bromide incorporation factor (BIF)Emerging DBPsDrinking water treatment

a b s t r a c t

Ozone has been widely used for drinking water treatment recently. This study was conducted to inves-tigate the effect of dosing ozone on the formation potentials and speciation of disinfection by-products(DBPs, brominated DBPs in particular) during subsequent chlorination. Trihalomethanes (THMs), trihalo-acetic acids (THAAs), dihaloacetic acids (DHAAs), dihaloacetonitriles (DHANs), chloral hydrate (CH) andtrichloronitromethane (TCNM) were included. The results showed that the yields of THMs, THAAs andDHAAs reached the maxima at 1.83, 0.65 and 0.56 lM, respectively, corresponding to an ozone doseapproximately at 2 mg L�1. The formation potentials of CH and TCNM increased, while that of DHANdecreased, with the increase of ozone dose up to 6 mg L�1. The bromide incorporation factor values ofTHMs, THAAs, DHAAs and DHANs increased from 0.62, 0.37, 0.45 and 0.39 at O3 = 0 mg L�1 to 0.89,0.65, 0.62 and 0.89 at O3 = 6 mg L�1, respectively. It indicated that the use of ozone as a primary disinfec-tant may cause a shift to more brominated DBPs during subsequent chlorination, and the shift may bemore evident with increased ozone dose. The total percentage of brominated DBPs (as bromide) reachedthe maximum value of 55% at 2 mg L�1 ozone dose.

� 2014 Published by Elsevier Ltd.

1. Introduction

Ozone has been increasingly used for drinking water treatmentin order to comply with the water regulations that become morestringent and to satisfy the demand for higher water quality(Grasso et al., 1989; Guo and Ma, 2007; Chiang et al., 2009).According to a survey conducted in 2007 in the United States, 9%of the water utilities used ozone as a primary disinfectant, whilethe ratio was only 2% in the 1998 survey (Hua and Reckhow,2013). In China, the process of ozone in combination with biologi-cally active carbon (BAC) had a total drinking water treatmentcapacity at approximately 20 million m3 d�1 by 2013 (Hong et al.,2013). Ozone is a strong oxidant and is very effective to controlthe color, odor and taste, and iron and manganese problems (Lin

et al., 2013). Ozone is also frequently used as a disinfectant, pri-marily for the inactivation of chlorine-resistant microorganismssuch as Giardia and Cryptosporidium (Burns et al., 2008). Becauseozone is unstable under typical drinking water conditions, chlorineor chloramine is added following ozonation as the disinfectant inthe distribution systems.

Chlorination and chloramination can lead to the formation of avast number of disinfection by-products (DBPs). Many DBPs havedefinitive adverse health impact even at very low concentrationlevels, and some DBPs are regulated by various drinking waterquality standards. The DBP occurrence levels in the finished watercan be affected by the dosing of ozone to the treatment train.Ozone can react with natural organic matter (NOM) and otherDBP precursors in the water and change their properties(Swietlik et al., 2004). Previous studies showed that the levels ofmany DBPs, e.g. total trihalomethanes (THMs) and haloacetic acids

DO

C (

mg

L-1

)

1.0

1.5

2.0

2.5

3.0

3.5

UV

254

(m-1

)

10

15

20

25

30

35

DOCUV254

516 Y. Mao et al. / Chemosphere 117 (2014) 515–520

(HAAs), could be substantially reduced when ozone was used,primarily ascribed to the decreased DBP precursor concentrationand the reduced chlorine or chloramine demand (Hu et al., 1999;Galapate et al., 2001; Chaiket et al., 2002; Ma, 2004; Chin andBérubé, 2005). However, some studies (Plummer and Edzwald,2001) found that ozonation enhanced the formation of THMs.The differences in the observed effects of ozonation on DBP forma-tion may be attributed to the different ozone dosages. In addition,ozonation would enhance the formation of some emerging DBPs.One notable example is the enhancing effect on the formation ofhalonitromethanes (HNMs) (Hu et al., 2010). Detailed underlyingmechanisms could be found in von Gunten (2003a, 2003b).

Every natural fresh water contains bromide at a concentrationfrom �10 to >1000 lg L�1 (Flury and Parritz, 1993). In additionto chlorinated DBPs, brominated DBPs can also be formed in theprocess of chlorination or chloramination. The cytotoxicity andgenotoxicity of brominated DBPs were shown much higher thanthat of the solely chlorinated analogs (Westerhoff et al., 2004;Richardson et al., 2007). Formation of brominated DBPs could beaffected by dosing ozone into the treatment system. On the onehand, ozone is such a strong oxidant that can oxidize bromidevia hypobromite to bromate; on the other hand, ozone can decom-pose the hydrophobic NOM of larger molecular weights into thehydrophilic organic substances of smaller molecular weightswhich leads to more formation of brominated DBPs (Swietliket al., 2004). It appeared that the bromine element was more easilyincorporated into hydrophilic substances than hydrophobic sub-stances (Amy et al., 1998; Liang and Singer, 2003; Huang et al.,2004; Wert and Rosario-Ortiz, 2011).

This study was conducted mainly to quantitatively investigatethe effect of ozonation on the formation of brominated DBPsduring subsequent chlorination. The ozone dosage was varied toreveal its effect on both DBP formation and speciation. A total ofeighteen DBPs in six groups were included that cover most DBPsof significant abundance in drinking water. These included THMs,trihaloacetic acids (THAAs), dihaloacetic acids (DHAAs), dihao-acetonitriles (DHANs), chloral hydrate (CH), and trichloronitrome-thane (TCNM).

2. Materials and methods

2.1. Synthetic raw water

The raw water was synthetic water that was prepared accordingto the recipe given in Table 1 (Liu et al., 2003). Humic acid at3.0 mg L�1 as dissolved organic carbon (DOC) was adopted tosimulate the NOM in typical surface waters. The bromide concen-tration was deliberately set at a relatively high value (300 lg L�1).High concentration of bromide in the raw water is not uncommon,especially where the water is influenced by seawater intrusion(Huang et al., 2003; Richardson et al., 2003). The pH value was con-trolled at 8.0 ± 0.1 by using carbonate.

2.2. Experimental procedure

Ozonation batch experiments were carried out in a thermostatreactor (1.14 L) in a water bath (20 ± 1 �C). The synthetic raw waterwas added into the reactor firstly before a saturated ozone solutionwas added by using a syringe with its needle penetrating through

Table 1The water qualities for the synthetic raw water.

Parameter Ca2+ Mg2+ Na+ Total carbonate Cl� SO42�

Concentration (mM) 0.73 0.42 1.52 1.5 1.44 0.43

septa on the top of the reactor. The saturated ozone solution (atabout 30 mg L�1) was prepared freshly by continuously bubblingozone-containing oxygen gas (from an ozone generator (Newland,Model NLO-20, China)) into cold de-ionized water (at 4 �C) using adiffuser. No headspace was left in the reactor to avoid the loss ofdissolved ozone and any formed volatile DBPs through thewater–air interface. The respective volumes of the simulated natu-ral water and saturated ozone solution were determined by therequired ozone dosage (ranging from 0 to 6 mg L�1). The reactionwill last for 20 min under magnetic stirring. And then 5 min ofnitrogen stripping was used to quench the residual O3. One aliquotof sample filtered with a 0.45 lm membrane was taken for theanalysis of bromide, bromate, UV254, and DOC. Another aliquot ofsample was taken for the determination of formation potentialsof the concerned DBPs according to the uniform formation condi-tions (UFC) protocol (Summers et al., 1996). After incubation for24 h, a stoichiometric amount of sodium thiosulfate was addedto quench the residual chlorine.

2.3. Analytical methods

THMs, DHANs, CH and TCNM were determined according toUSEPA Method 551.1 (USEPA, 1995) by using a GC (Agilent7890A, Santa Clara, USA) equipped with a DB-1 capillary column(30 m � 0.25 mm � 0.25 lm, Agilent, USA) and an electron capturedetector. THAAs and DHAAs were determined according to USEPAMethod 552.3 (USEPA, 2003) by using a GC (Agilent 7890A, SantaClara, USA) equipped with a DB-1701 capillary column(30 m � 0.25 mm � 0.25 lm, Agilent, USA) and an electron capturedetector. All of the DBP standards were purchased from the Sigma–Aldrich company (Germany).

Ozone concentration was determined spectrophotometrically at610 nm by using the indigo method. Bromate and bromide weremeasured by an IC (Metrohm 761, Switzerland) which had a supp7250/4.0 mm anion column, a 100 lL loop and a conductivity detec-tor. The mobile phase was sodium carbonate solution (3.6 mMNa2CO3) and the flow rate was 0.8 mL min�1. DOC was determinedby a total organic carbon analyzer (Shimadzu TOC-VCPH). Chlorinewas determined by the N, N-diethyl-p-phenylenediamine titrimet-ric method using a Hach chlorine detector (Pocket Colorimeter II).

3. Results and discussion

3.1. Effects of ozonation on DBP formation

As expected, ozonation at the dosage of this study (1–6 mg L�1)showed a minor DOC removal (Fig. 1). Previous studies haveshowed that the typical reduction in DOC ranged from 5% to 20%

Ozone dose (mg L-1)

0 1 2 3 4 5 60.0

.5

0

5

Fig. 1. Variations of DOC and UV254 values with ozone dose.

TH

Ms

0.0

.2

.4

.6

.8

1.0

1.2CHCl3

CHCl2Br

CHClBr2

CHBr3

TH

AA

s

0.0

.1

.2

.3 TCAABDCAADBCAA

.3DCAABCAA)

(a)

(b)

(c)

Y. Mao et al. / Chemosphere 117 (2014) 515–520 517

under typical ozone dose of 2–5 mg L�1 (Can and Gurol, 2003; Leeet al., 2009). However, it is clear from Fig. 1 that ozone was quiteeffective for the removal of UV absorbing compounds (e.g. havingdouble bonds and aromatic structure), leading to decreased SUVAvalues. SUVA (specific UV absorbance at 254 nm) is the ratio ofUV254 to DOC, which has been used as an indicator of DBP precur-sors and humic content of the NOM (Weishaar et al., 2003). In gen-eral, water with high SUVA value is rich in hydrophobic and highmolecular organic matter. These results indicated that ozonationaltered the NOM properties from hydrophobic matters into hydro-philic organic substances of smaller molecular weights.

Fig. 2 illustrates the effects of ozone dose on DBP formation dur-ing subsequent chlorination. The nine HAAs were grouped intoTHAAs, DHAAs and monohaloacetic acids (MHAAs). THAAs arethe sum of trichloroacetic acid (TCAA), bromodichloroacetic acid(BDCAA), dibromochloroacetic acid (DBCAA), and tribromoaceticacid (TBAA), and DHAAs are the sum of dichloroacetic acid (DCAA),bromochloroacetic acid (BCAA) and dibromoacetic acid (DBAA).The MHAA concentrations were low and not included in thefollowing discussion. In general, the THM, THAA and DHAA yieldsincreased and then decreased as ozone dose increased. Themaximum concentrations of THM, THAA, and DHAA when ozonedose was at around 2 mg L�1 reached 1.83, 0.65, 0.56 lM, respec-tively, which were about 1.38, 1.23, and 1.43 times higher thanthat without ozonation, respectively. It may because that thestrong oxidant ozone oxidized the large fractions of humic acidthat are hard to react with chlorine to low-molecular weightorganic matter, resulting in more DBP precursors. Ozone may oxi-dize NOM and produce greater amounts of methyl-ketone-likestructures, which are considered major DBP precursors (Yanget al., 2012). However, when ozone dose increased to 6 mg L�1,THM and THAA yields showed net decreases of 10% and 18%,respectively, whereas DHAA yield still presented 6% net increase.The relatively similar trends observed for the THM and THAAyields at various ozone doses are likely linked to the fact that bothDBP classes have similar precursors and formation pathways(Reckhow and Singer, 1985). Hua and Reckhow (2007) investigatedDBP formation from various NOM fractions. Results showed thathydrophobic NOM generally formed more THMs and THAAs thanthe corresponding hydrophilic NOM, whereas the hydrophilicNOM produced the highest DHAA yields among the NOM fractions.Results observed at higher ozone dose in this study may be attrib-uted to that DBP precursors of methyl-ketone-like structure werefurther ozonated to organic matter of lower molecular weightswhich were non-DBP precursors.

In addition to THMs, THAAs, and DHAAs, DHANs are anotherimportant class of DBPs because most of them are more toxic thanTHMs and HAAs. Ding et al. (2013) found that HANs were about923�, 116�, 92� and 34� more cytotoxic than THM4, HAAs,

THM THAA DHAA DHAN CH TCNM

DB

P y

ield

s (µ

M)

0.0

.5

1.0

1.5

2.0

DB

P y

ield

s (µ

M)

0.00

.05

.10

.15

.20O3 = 0 mg L-1

O3 = 1 mg L-1

O3 = 2 mg L-1

O3 = 3 mg L-1

O3 = 4 mg L-1

O3 = 5 mg L-1

O3 = 6 mg L-1

Fig. 2. Effects of ozone dose on DBP yields during subsequent chlorination.

Iodinated THMs and HNMs, respectively. Three DHANs weredetected in this study, which include dichloroacetonitrile (DCAN),bromochloroacetonitrile (BCAN) and dibromoacetonitrile (DBAN).As shown in Fig. 2, pre-ozonation reduced the yield of DHANs fromsubsequent chlorination at any ozone doses. As the ozone doseincreased from 1 to 6 mg L�1, the DHAN reduction rates increasedfrom 25% to 57%. The DHAN reductions caused by ozonation weregenerally larger than the reductions of THMs and THAAs. It isconsistent with the literatures that reported the typical order ofDBP formation potential (DBPFP) reductions by ozone: DHANs >THAAs > THMs > DHAAs (Reckhow and Singer, 1985; Yang et al.,2012; Hua and Reckhow, 2013).

Haloacetaldehydes are the third largest class of halogenatedDBPs on a weight basis (Krasner et al., 2006). In this study, the pri-ority haloaldehyde CH increased when ozone dosage increased andreached 0.15 lM at ozone dose of 6 mg L�1. A similar trend wasobserved for the effect of pre-ozonation on TCNM formation. It islikely that the concentrations of aldehydes and dissolved organicnitrogen species in the hydrophilic NOM were increased afterozonation, which were the major precursors of CH and TCNM(Hu et al., 2010; Yang et al., 2012). Previous studies demonstratedthat aldehydes and TCNM could be removed with biofiltration (e.g.BAC) (Weinberg et al., 1993; Chu et al., 2012). Therefore, the BACprocess may be used by water utilities after ozonation for betterDBP control.

3.2. Effects of ozonation on DBP speciation

Fig. 3 presents the effects of pre-ozonation on the speciation ofTHMs, HAAs, and DHANs. TBAA was not shown in this figure

0.0

.1

.2

DBAA

Ozone dose (mg L-1)

0 1 2 3 4 5 6

DH

AN

s

0.00

.02

.04

.06DCANBCANDBAN

DH

AA

sD

BP

yie

lds

(µM

(d)

Fig. 3. Effects of ozone dose on DBP speciation during subsequent chlorination.

518 Y. Mao et al. / Chemosphere 117 (2014) 515–520

because it was below the detection limit. It was observed that theeffects of ozonation on the concentration of individual specieswithin each DBP groups were quite different. Within the THMgroup, CHCl3 and CHCl2Br concentrations reached their maximawhen the ozone dose was 2 mg L�1; whereas the CHClBr2 concen-tration was the highest for an ozone dose at 4 mg L�1 and theCHBr3 concentration kept increasing with the ozone dose. Theeffect on the DHAA group was similar; while the highest DCAAand BCAA concentrations corresponded to an ozone dose at2 mg L�1, no inflection point could be observed for the DBAA con-centration. The effect on THAA group was different; the TCAA andDBCAA concentrations kept decreasing and increasing with theozone dose, respectively, while the BDCAA concentration was thehighest when the ozone dose was 2 mg L�1. Although the totalDHAN yield decreased with increasing ozone dose (Fig. 3d), theozone dose showed different impacts on each DHAN species. Whenthe ozone dosage increased, DCAN yield decreased rapidly, BCANyield decreased gradually, while DBAN yield increased continu-ously. It is clear that pre-ozonation shifts the formation of THMs,HAAs and DHANs to more brominated species during subsequentchlorination.

To obtain a better understanding of the effects of pre-ozonationon DBP speciation, bromine incorporation factor (BIF) is used toindicate the degree of bromine substitution in DBPs. Eqs. (1)-(4)present the calculations of the BIFs for THMs, THAAs, DHAA, andDHANs, respectively (Obolensky and Singer, 2005). As shown inFig. 4, the BIF values of these DBPs generally increased after ozon-ation, and the higher the ozone dose was, the higher the BIF valueswere. This confirmed that ozonation shifted the formation of DBPsto more brominated species. In addition, the BIF values of theseDBPs showed a general order of THMs > DHANs > DHAAs > THAAs.Although a BIF order of DHANs > THMs � DHAAs > THAAs wasobserved in the literatures (Hua et al., 2006; Hu et al., 2010),Yang et al. (2013) reported that bromine incorporation in THMswas higher than that in HAAs, and bromine incorporation in HAAswas higher than that in DHANs when using chlorine dioxide fol-lowed by chlorination of NOM. Therefore, the water characteristicsalso played an important role in DBP speciation.

BIF ðTHMsÞ ¼ ½CHBrCl2� þ 2½CHBr2Cl� þ 3½CHBr3�½CHCl3� þ ½CHBrCl2� þ ½CHBr2Cl� þ ½CHBr3�

ð1Þ

BIF ðTHAAsÞ ¼ ½BDCAA� þ 2½DBCAA� þ 3½TBAA�½TCAA� þ ½BDCAA� þ ½DBCAA� þ ½TBAA� ð2Þ

Ozone dose (mg/L)

0 1 2 3 4 5 6

BIF

0.0

.2

.4

.6

.8

1.0THMsTHAAsDHAAsDHANs

Fig. 4. Effects of ozone dose on DBP BIFs during subsequent chlorination.

BIF ðDHAAsÞ ¼ ½BCAA� þ 2½DBAA�½DCAA� þ ½BCAA� þ ½DBAA� ð3Þ

BIF ðDHANsÞ ¼ ½BCAN� þ 2½DBAN�½DCAN� þ ½BCAN� þ ½DBAN� ð4Þ

3.3. Effects of bromide addition point on brominated DBP formation

The effect of bromide addition point (before or after ozonation)was investigated to explore the mechanism for the shifts of morebrominated DBPs with pre-ozonation. As shown in Fig. 5, bromidespiked before or after ozonation has little effect on the organic DBPformation and speciation during subsequent chlorination. The onlyobvious difference was that bromide spiked before ozonationresulted in the formation of bromate. However, the concentrationof bromate was far below that of the brominated organic DBPs(Fig. 6), which will be discussed in detail later. This can beexplained by the competition kinetics of NOM and bromide forozone (von Gunten, 2003a). The concentration of humic acid wasalmost 10 times higher than that of bromide, and it was expectedthat most ozone added was consumed by the reactions with humicacid. Ozone alone can react with bromide and NOM to producebrominated DBPs including CHBr3, DBAA and DBAN (Huang et al.,2004). However, in this study, the yields of all brominated DBP spe-cies were below the detection limits when ozone was used alone(i.e. without subsequent chlorination). This indicated that the con-tributions to brominated DBPs from the reaction between HOBr(produced from the reaction between ozone and bromide) withNOM, and from the brominated intermediates formed by HOBrand NOM (that served as brominated-DBP precursors later) wereinsignificant under the conditions of this study. The NOM transfor-mation caused by ozonation, i.e. from hydrophobic natural NOM oflarger molecular weights to the hydrophilic organic substances ofsmaller molecular weights, was the major mechanism for the shiftsto more brominated DBPs.

3.4. Effects of ozonation on bromide distribution

When concentrations of bromate, brominated THMs, bromi-nated THAAs and brominated DHAAs as well as bromide ion at var-ied ozone doses were known, mass balance for bromide could beanalyzed for its distribution in the water (Fig. 6). A minimum of22% of the bromide was contained in brominated THMs whichwere the main products after chlorination at various ozone doses.When the ozone dose increased from 0 to 6 mg L�1, the percentageof bromate (in terms of bromide) increased from 0 to 15%, while

Fig. 5. Effects of bromide addition point on DBP formation and speciation duringsubsequent chlorination. (First bar: bromide spiked after ozonation; second bar:bromide spiked before ozonation.)

0 1 2 3 4 5 60

20

40

60

80

100

Pro

porti

on o

f Br i

n di

ffere

nt D

BP

s (%

)

Ozone dose (mg L-1)

others DHANs HAAs THMs BrO3-

Fig. 6. Bromide mass balance at different ozone doses.

Y. Mao et al. / Chemosphere 117 (2014) 515–520 519

that of the brominated THMs, THAAs and DHAAs reached theirmaximum values of 38%, 9%, and 9%, respectively, at ozone doseof 2 mg L�1. The total percentage of the brominated DBPs (in termsof bromide) ranged from 32% to 55% under the conditions of thisstudy. It is consistent with Krasner et al. (2006) that reported thetypical percentage of total organic bromide accounted for by theknown halogenated DBPs ranged from 6% to 58%.

It appears that dosing ozone may increase the risk by DBPs notonly because of increased total DBPFP, but also because ofincreased brominated DBPFP. The ozone dose which causes thehighest risk by DBPs varies with water quality. In our experimentconditions, ozone dose at 2 mg L�1 caused the highest risk. Itimplies that the use of ozone as a primary disinfectant does notnecessarily reduce the DBPFP under any conditions, and theapplied ozone dose need to be taken into serious considerationby water utilities, especially of those treating high-bromide waters.

4. Conclusions

In this study, 3 mg L�1 (calculated as DOC) humic acid was usedto simulate NOM, pH was controlled at 8.1 ± 0.1, bromide concen-tration was prepared at about 300 lg L�1, and ozone dose wasranged from 0 to 6 mg L�1. The ozonation was carried out in abatch reactor for 20 min. After ozonation, subsequent chlorinationwas adopted under the UFC protocol. Under such conditions, someconclusions can be drawn as follows:

(1) THM, THAA and DHAA formation potentials reached themaximum values of 1.83, 0.65 and 0.56 lM, respectively,at 2 mg L�1 ozone dose. CH and TCNM formation potentialsincreased while DHAN formation potential decreased withincreased ozone dose. In drinking water treatment, the useof ozone as a primary disinfectant may increase DBP forma-tion during subsequent chlorination.

(2) The yields of the principal chlorinated DPBs (i.e. CHCl3 andDCAA) and brominated DBPs (i.e. CHCl2Br, BCAA and BDCAA)reached the maximum at ozone dose of 2 mg L�1, whereasthe increasing rates of the brominated DBPs were muchhigher than that of the chlorinated DBPs. The ratio of thebrominated DBPs increased significantly after pre-ozona-tion. Because the brominated DBPs are more cytotoxic thanthe chlorinated DBPs, the health risk of DBPs caused by pre-ozonation followed by subsequent chlorination may bemuch higher than that caused by increase of the DBP yields.

(3) The BIF values of THMs, THAAs, DHAAs, and DHANs,increased by 44%, 78%, 38%, and 125% when ozone doseincreased from 0 to 6 mg L�1, respectively. Such results

indicated that the use of ozone as a primary disinfectantmay cause a shift to more brominated DBPs during subse-quent chlorination, and the shift may be more evident withincreased ozone dose. According to the bromide mass bal-ance analysis, the total percentage of brominated DBPs (asbromide) reached the maximum value of 55% at 2 mg L�1

ozone dose.

Acknowledgement

The authors wish to acknowledge the financial support fromNational Natural Science Foundation of China (No. 51290284,51278269).

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