Competition Impact of Sulfate on NOM Removal by Anion-Exchange

Sep 10, 2013 - organic matter (NOM) removal in waters with low specific UV absorbance (SUVA) ... The natural organic matter (NOM) present in water sou...
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Competition Impact of Sulfate on NOM Removal by Anion-Exchange Resins in High-Sulfate and Low-SUVA Waters Nuray Ates*,† and Fatma Burcin Incetan‡ †

Department of Environmental Engineering, Faculty of Engineering, Erciyes University, 38039 Kayseri, Turkey Directorate of Environment and Urbanization of Kayseri, Ministry of Environment and Urbanization, 38039 Kayseri, Turkey

‡

S Supporting Information *

ABSTRACT: The main objective of this study was to investigate the affinity and efficiency of anion-exchange resins on natural organic matter (NOM) removal in waters with low specific UV absorbance (SUVA) and high sulfate. Two low-SUVA surface waters (Camlidere and Kesikkopru) with different sulfate concentrations were used. NOM removal batch experiments using MIEX and DOWEX 11 resins were conducted at different resin doses. NOM removals by both resins were higher in low-sulfatecontent than in high-sulfate-content waters. Continuous sorption tests were then conducted using both resins. To better investigate the effect of sulfate on dissolved organic carbon (DOC) removal, sulfate spiking was employed with different influent sulfate concentrations in Camlidere (17−300 mg/L) and Kesikkopru (390−600 mg/L) water samples. The decrease in NOM removal from 60% to 20% observed with increasing influent sulfate concentration indicates that sulfate content is a more important parameter influencing DOC removal than the contents of other anions such as bicarbonate, nitrate, and bromide.

1. INTRODUCTION The natural organic matter (NOM) present in water sources leads to disinfection byproducts (DBPs) by reacting with common disinfectants (e.g., chlorine, ozone, chlorine dioxide, chloramines). Application of major disinfectants and their combinations in disinfection processes produces approximately 600−700 DBPs of which only a small percentage have been quantified in drinking waters.1,2 The major strategy for minimizing and controlling DBPs is to remove NOM from water sources before they come into contact with disinfectants. NOM in source waters can be removed directly or indirectly by various treatment processes including enhanced coagulation,3,4 activated carbon adsorption,5,6 and membrane filtration.7,8 Anion exchange is considered as an alternative process for the removal of NOM, because the majority of organic compounds in natural waters are in ionic (acidic) form in natural waters.9 Although the high potential of anion-exchange resins for NOM removal was first reported at the end of the 1970s,10 the resin process has recently attracted increasing attention because of magnetic ion-exchange resin (MIEX), which was developed especially for the removal of NOM. NOM can be removed in the range of 30−90% by anionexchange resins depending on the source water and NOM characteristics and the resin type.11,12 Hydrophilic (lower molecular weight, higher carboxylic group content) and charged NOM components are potential targets.11,13 Generally, polyacrylic, macroporous, strong-base anion-exchange resins provide better NOM removal than other resin types.9,13−15 Among available resins, MIEX resin is a promising anion exchanger because of its polyacrylic, macroporous structure with quaternary amine functional groups and resin beads that are 2−5 times smaller than those of traditional resins, providing much greater external surface areas.12,16 MIEX resin appears to remove a wide range of molecular-weight acid fractions with both hydrophobic and hydrophilic characteristics;17 never© 2013 American Chemical Society

theless, it has a greater preference for hydrophobic acids having higher specific UV absorbance (SUVA) values.17−20 Reported dissolved organic carbon (DOC) removal and decrease of the UV absorbance at a wavelength of 254 nm (UV254) by MIEX in the literature17−19,21−25 range from 35% to 85% and from 40% to 75%, respectively, depending on the NOM characteristics and water quality. In addition to NOM, the anion-exchange process has the potential to remove negatively charged inorganic constituents including sulfate, nitrate, sulfide, bromide, and arsenate from source waters.18,26 It is known that polymeric resins have higher priority for hydrophobic and aliphatic organics than for other inorganic anions.15,27,28 because of the higher sorption affinities of these resins for organic substances, which is attributed to hydrophobic interactions resulting from the nonpolar moiety of the aromatic organics.29 Nevertheless, the extent of NOM removal depends on competition between NOM and anions based on their affinities for the resin and amounts in the source waters.21,22,26 Low alkalinity and low sulfate contents limit the anion competition in NOM removal by anion-exchange resins.12 On the other hand, NOM removal can be enhanced in the presence of bicarbonate and chloride because of increasing ionic strength, which results in the retention and adsorption of NOM onto polystyrene resins.13,15 Anion-exchange resins can remove sulfate and nitrate rapidly and almost completely.30 However, the presence of sulfate has a strong effect on NOM removal because of the high selectivity of resins for sulfate, so that elevated sulfate concentrations tend to inhibit DOC removal.9,16,20,31,32 Therefore, a general trend has been reported in the literature12,32 that increasing sulfate concentration has a Received: Revised: Accepted: Published: 14261

June 8, 2013 September 3, 2013 September 10, 2013 September 10, 2013 dx.doi.org/10.1021/ie401814v | Ind. Eng. Chem. Res. 2013, 52, 14261−14269

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the corresponding dams using 25-L polypropylene containers. All water samples were immediately characterized for DOC, UV254, pH, bromide, sulfate, nitrate alkalinity, total hardness, conductivity, total dissolved solids (TDS), and turbidity and stored at 4 °C in the dark until use. The physicochemical characteristics of the raw Camlidere and Kesikkopru waters are reported in Table 1. In all raw and treated waters, carbonate

negative impact on NOM removal by anion exchange because of the competition phenomenon. NOM removal by anion exchange depends strongly on the NOM characteristics, the relative proportion of NOM fractions, the anion-exchange resin type and properties, the presence and amount of other anions, and the physicochemical characteristics of the source waters. The removal of NOM by anion exchange is more effective in waters with SUVA254 > 3 L (mg of C)−1 m−1 and sulfate < 50 mg/L.18−20,33 The reported SUVA values in previous studies12,16,20,32,34−38 were mostly higher than 2.0 L (mg of C)−1 m−1, sulfate concentrations ranged from 6 to 110 mg/L, and corresponding DOC removals were reported to be between 44% and 81%. The highest sulfate concentration reported in the literature was 246 mg/L in the study of Budd and co-workers,16 who observed DOC removals of 23−46%. However, the reservoirs used as the drinking water sources in Turkey consist mostly of waters with low SUVA values [average of 1.72 L (mg of C)−1 m−1] of nonhumic and aliphatic character.39 In addition, certain water sources (e.g., Kesikkopru reservoir) have a considerably high sulfate content. Because only one study16 reported source water with low SUVA and a high sulfate level, discussion of the performance of anionexchange resins and the impact of sulfate competition on NOM removal in low-SUVA, high-sulfate waters is still limited in the literature. The main objective of this study was to systematically investigate the effectiveness and applicability of anion exchangers for the removal of nonhumic and low-aromatic NOM in high-sulfate waters. For this purpose, Camlidere and Kesikkopru waters were selected based on their NOM characteristics and sulfate contents. The Camlidere source, with the highest reservoir volume, is one of the main water sources of the Ivedik water treatment plant (WTP) providing drinking water for a population of almost 5 million in Ankara, Turkey. The Kesikkopru source was connected to the treatment plant in 2007, and since then, it has been blended with Camlidere water from time to time in cases of necessity. The Camlidere reservoir is situated 60 km southwest of Ankara and has an annual potable water capacity of 130−150 million m3. The Kesikkopru reservoir is located on the Kizilirmak River 128 km southeast of Ankara. The water capacity of the Kesikkopru reservoir is about 95 million m3. Both reservoirs have moderate levels of NOM with 4.5−5.5 mg/L as DOC having mainly nonhumic components and low aromaticity based on their SUVA values, which are less than 2 L (mg of C)−1 m−1. The Kesikkopru source water has a sulfate concentration as high as 450 mg/L on average, with peaks of up to 1000 mg/L from time to time, whereas Camlidere water is usually low in sulfate concentration ( DOC > bicarbonate for low-sulfate water, the sequence changed to DOC > UV254 ≈ sulfate > bicarbonate for high-sulfate water. Contrary to reports in the literature, MIEX resin has higher affinity for sulfate than DOC at lower sulfate concentration.27 DOWEX 11 had a better removal performance for aromatic organics than MIEX resin in high-sulfate water, and the sequence of affinity was UV254 > DOC > sulfate > bicarbonate. Both of the source waters had lower SUVA values, at 1.68 L (mg of C)−1 m−1 (Camlidere water) and 0.71 L (mg of C)−1 m−1 (Kesikkopru water), and over 70% SUVA removal was observed for both resins in Camlidere water. However, SUVA was increased by 30% and decreased by 25% of its influent values by MIEX and DOWEX 11, respectively, in Kesikkopru water (data not shown). The increase in SUVA in the effluent showed that more DOC was removed corresponding to UV254 removal by MIEX in Kesikkopru water. These results indicate that higher sulfate concentration shifts preferential removal of

Figure 3. Impact of multiple-loading tests of MIEX resin (10 mL/L resin dose) on DOC and sulfate removals in (a) Camlidere water and (b) Kesikkopru water. Error bars show standard deviations of duplicate samples. Average data for each parameter are reported.

Camlidere and Kesikkopru waters, respectively. For Camlidere water, DOC effluents varied between 1.28 and 2.00 mg/L up to 1500 BV loadings without any saturation (Figure 3a), and DOC concentration was 2.1 mg/L on average with 61% removal efficiency in the composite sample of 1500 BVs. In contrast to the variation in DOC, the variation in UV254 was more stable and varied between 0.0065 in 300 BV and 0.0153 in 1500 BV, below 20% of its infleunt value (Figure S3, Supporting Information). On the other hand, the influent sulfate concentration of 17 mg/L was reduced to 3 mg/L with 82% removal efficiency and followed a consistent trend up to 1500 BV loadings. These results indicated, overall, that the 14265

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resins could be loaded up to 1500 BVs or more without regeneration to treat Camlidere water. In Kesikkopru water, the trend of multiple-loading of MIEX was quite different from that in Camlidere water (Figure 3b). For loadings from 100 to 500 BVs, effluent DOC concentrations decreased from 2.8 to 2.1 mg/L. After 800 BVs, the DOC concentration stabilized at about 2.5 mg/L in consecutive batches. In the composite sample of 1500 BVs, the DOC concentration was 2.6 mg/L on average, with 46% removal efficiency. A similar result was reported by Verdickt and co-workers49 that a major part of the resin capacity was occupied by sulfate (100 mg/L of average raw-water sulfate concentration) and far fewer effective resin sites were left for DOC removal. In addition, 1000 BVs was determined in that study as the optimum consecutive multipleloading amount for overall removal efficiencies for NOM, sulfate, nitrate, and alkalinity. Although the effluent waters from Kesikkopru water have higher UV254 values than effluent waters from Camlidere water, the UV254 values are still very low (>0.020) and stable in all consecutive loadings. The UV254 profile varied between 0.0155 in 100 BVs and 0.0203 in 1500 BVs and on average 50% of its initial value was removed (see Figure S3 of the Supporting Information). Even though the SUVA level of Camlidere raw water was higher than that of Kesikkopru raw water, the SUVA values of both effluent waters were similar, around 0.6−0.7 L (mg of C)−1 m−1. On average, 72% of SUVA was removed from Camlidere water, and the percentage removal of SUVA in Kesikkopru water was 11%. Similar results were reported by Singer et al.17 in pilot trials performed on four different surface waters. The lowest DOC (35%) and UV-absorbing substances (55%) were observed at high sulfate (230−250 mg/L), which they attributed to a relatively high sulfate and lower SUVA in raw water. Operating the MIEX resin continually had almost no beneficial effect on sulfate removal in high-sulfate water (Kesikkopru) and provided lower DOC removal. The results of DOWEX 11 continuous-flow tests for DOC and sulfate removals with respect to bed volumes in Camlidere and Kesikkopru waters are shown in panels a and b, respectively, of Figure 4. As seen from Figure 4a, the effluent DOC concentration (about 1.1 mg/L) was stable up to about 1500 BVs; then, the breakthrough phenomenon was observed, and the effluent DOC concentration increased substantially by passing water through the column for Camlidere water. Similarly to the DOC profile, sulfate followed the same trend. Nevertheless, sulfate reached the breakthrough point before DOC at around 1000 BVs. The release of sulfate (1−2 mg/L) before breakthrough indicates the development of short circuiting because the ratio of the internal column diameter to the particle diameter was less than 50:1. On the other hand, a gradual increase was observed in UV254 from 0.014 to 0.057 after 100 BVs (Figure S4, Supporting Information). Despite the increasing UV254 value, DOC was almost constant around 1.1 mg/L in the range of 100−1500 BVs. In the composite sample of 1500 BVs, the removals of DOC and UV254 were 75% and 53%, respectively. In Kesikkopru water, the breakthrough phenomenon occurred at 600 BVs based on the effluent DOC. Up to 600 BVs, the DOC concentration stabilized around 2.0−2.2 mg/L and then substantially increased. According to the UV254 profile, there was a gradual increase in UV254 valuen despite the DOC profile (Figure S4, Supporting Information). At the breakthrough point for DOC, the removal efficiencies for DOC and UV254 were 58% and 71%, respectively. Breakthrough for

Figure 4. Impact of continuous-column tests of DOWEX 11 resin on the percentage removals of DOC and sulfate in (a) Camlidere water and (b) Kesikkopru water. Error bars show standard deviations of duplicate samples. Average data for each parameter are reported.

sulfate was observed before DOC breakthrough at around 450 BV, as was the case for Camlidere water. Sulfate removal was over 95% before the occurrence of breakthrough in both waters. The fact that more DOC removal was observed in Camlidere water than in Kesikkopru water using DOWEX 11 indicates that sulfate mostly competed with the nonhumic fraction of DOC, so that the DOC removal efficiency was reduced. Therefore, higher UV254 removal was observed in the highsulfate water (Kesikkopru water). 3.3. Impact of Sulfate Concentration on NOM Removal by MIEX Resin. To evaluate the impact of the sulfate concentration on NOM removal, a wide range of sulfate concentrations was spiked in Camlidere (17−300 mg/L) and Kesikkopru (390−600 mg/L) waters and led to contact from 5 to 30 min with a MIEX resin dose of 10 mL/L. DOC removals with respect to sulfate concentration are given in Figure 5.

Figure 5. Impact of elevated influent sulfate concentration on DOC removal by MIEX resin (resin dose = 10 mL/L). Error bars show standard deviations of duplicate samples. Average data are reported. 14266

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DOC removal was reduced from 60% to 35% in Camlidere water. On the other hand, DOC removal ranged from 30% to 20% in Kesikkopru water. The results obtained from all samples and presented in Figure 5 indicate that DOC removal decreased from 60% to 20% as the influent sulfate concentration increased from 17 to 600 mg/L, respectively. Indeed, this finding is consistent with literature reports9,16,19,20,31,32 that anion-exchange resins tend to have a high selectivity for sulfate and elevated influent sulfate concentrations inhibit DOC removal by anion exchange. The changes in SUVA values were rather different from the results in the literature that MIEX would preferentially remove UVabsorbing, relatively hydrophobic organic fractions.19,23,24 However, the SUVA values in MIEX-treated water samples increased from 0.22 to 0.50 L (mg of C)−1 m−1 as the sulfate concentration was increased from 17 to 150 mg/L and remained stable as the sulfate concentration was increased further from 150 to 300 mg/L in Camlidere [raw-water SUVA = 1.68 L (mg of C)−1 m−1]. On the other hand, the SUVA was almost constant at 0.50 L (mg of C)−1 m−1 at all sulfate concentrations in Kesikkopru water [raw-water SUVA = 0.71 L (mg of C)−1 m−1]. The lower removal rate of UV254 compared to DOC resulted in higher SUVA values with increasing sulfate concentration in MIEX-treated samples. This means that the relative removal of non-UV-absorbing organics is higher than the removal of UV-absorbing organics at lower sulfate concentrations. These results indicate that the performance of MIEX in the removal of UV-absorbing organics decreases with increasing influent sulfate concentration in low-SUVA water sources. Although NOM removals were obtained from two different source waters, each with different DOC and SUVA values, a strong correlation (R2 = 0.96) was observed between DOC removal and influent sulfate concentration. This result indicates that the influent sulfate concentration is a more important parameter than other water quality parameters (such as bicarbonate, nitrate, and bromide) at high sulfate contents. As mentioned previously, the raw-water sulfate concentrations reported in the literature12,15,20,38 were much lower, and the source waters mostly had SUVA values higher than 2 L (mg of C)−1 m−1. Because there is only one study on NOM removal by anion-exchange resin using source water with 246 mg/L sulfate concentration,16 the discussion of the impact of sulfate on NOM removal in low-SUVA waters is limited. Therefore, the results of this study indicate more obviously the impact of sulfate on NOM removal by MIEX resin in water sources having low SUVA values. Also, there are no published data presenting the correlation between NOM removals and influent sulfate concentration. On the other hand, sulfate removals were also observed for different sulfate background concentrations; the removal rate of sulfate and the MIEX resin capacity for sulfate removal with respect to different influent sulfate concentrations are presented in panels a and b, respectively, of Figure 6. As shown in Figure 6a, sulfate removal was almost constant at over 90% efficiency up to 150 mg/L sulfate concentration; however, the percentage removal of sulfate decreased sharply from 90% to 20% at higher sulfate concentrations (600 mg/L). The resin capacity increased with increasing influent sulfate concentration up to 150 mg/L, and equilibrium conditions developed between the resin and sulfate beyond this dose (Figure 6b). The removal rate of sulfate and the resin capacity for sulfate removal followed the same trend even for data collected from two

Figure 6. Impact of elevated sulfate concentration on sulfate removal by MIEX resin (resin dose = 10 mL/L): (a) percentage removal and (b) capacity. Error bars show standard deviations of duplicate samples. Average data are reported.

different source waters with different DOC and SUVA values, as was also the case in the relation between DOC removal and influent sulfate concentration. According to this result, MIEX resin provided almost complete sulfate removal unless the sulfate concentration exceeded 150 mg/L. Overall, MIEX treatment is not likely to be beneficial in removing sulfate above 150 mg/L because of developing equilibrium conditions between the resin and sulfate anion.

4. CONCLUSIONS This study investigated the competition effect of sulfate on NOM removal in low-SUVA waters [0.71 and 1.68 L (mg of C)−1 m−1] with low (17 mg/L) and high (390 mg/L) sulfate contents. Furthermore, this was the first study to investigate the correlation between NOM removal and influent sulfate concentration. DOC removal at a MIEX resin dose of 10 mL/L decreased from 70% to 54% as the sulfate concentration was increased from 17 to 390 mg/L. UV254 and sulfate were almost completely eliminated in low-sulfate water; however, their removal decreased to around 45% in high-sulfate water. The DOC removals by DOWEX 11 were 60% and 40% in low- and high-sulfate waters, respectively. Whereas over 80% of the sulfate was removed in low-sulfate water, the rate was 60% in high-sulfate water. In the MIEX process, whereas the sequence of removal and affinity for anions was UV254 ≈ sulfate > DOC > bicarbonate in low-sulfate water, the sequence was changed to DOC > UV254 ≈ sulfate > bicarbonate in high-sulfate water. Controversially, DOWEX 11 exhibited better removal performance for aromatic organics than MIEX resin in high-sulfate water, and the sequence of affinity was UV254 > DOC > sulfate > bicarbonate. Negligible bromide and nitrate removals were observed with 14267

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(6) Alvarez-Uriarte, J. I.; Iriarte-Velasco, U.; Chimeno-Alanis, N.; Gonzalez-Velasco, J. R. The Effect of Mixed Oxidants and Powdered Activated Carbon on the Removal of Natural Organic Matter. J. Hazard. Mater. 2010, 181, 426. (7) Hong, S.; Elimelech, M. Chemical and Physical Aspects of Natural Organic Matter (NOM) Fouling of Nanofiltration Membranes. J. Membr. Sci. 1997, 132, 159. (8) Li, Q.; Elimelech, M. Organic Fouling and Chemical Cleaning of Nanofiltration Membranes: Measurement and Mechanisms. Environ. Sci. Technol. 2004, 38, 4683. (9) Fu, P.L.-K.; Symons, J. M. Removing Aquatic Organic Substances by Anion Exchange Resins. J. Am. Water Works Assoc. 1990, 82, 70. (10) Snoeyink, V. L. Removal of Organics with Adsorbents Other Than Activated Carbon. Presented at the AWWA Water Quality Technology Conference, Part II, San Francisco, CA, Jun 24−29, 1979. (11) Bolto, B.; Dixon, D.; Eldridge, R.; King, S.; Linge, K. Removal of Natural Organic Matter by Ion Exchange. Water Res. 2002, 36, 5057. (12) Humbert, H.; Gallard, H.; Suty, H.; Croue, J.-P. Performance of Selected Anion Exchange Resins for the Treatment of a High DOC Content Surface Water. Water Res. 2005, 39, 1699. (13) Croue, J. P.; Violleau, D.; Bodaire, C.; Legube, B. Removal of Hydrophobic and Hydrophilic Constituents by Anion Exchange Resin. Water Sci. Technol. 1999, 40, 207. (14) Bolto, B.; Dixon, D.; Eldridge, R.; King, S. Removal of THM Precursors by Coagulation or Ion Exchange. Water Res. 2002, 36, 5066. (15) Boyer, T. H.; Singer, P. C. Stoichiometry of Removal of Natural Organic Matter by Ion Exchange. Environ. Sci. Technol. 2008, 42, 608. (16) Budd, G. C.; Long, B.; Edwards, J. C.; Singer, P. C.; Meisch, M. Evaluation of MIEX Process Impacts on Different Source Waters; AwwaRF Report 91067F; American Water Works Association Research Foundation: Denver, CO, 2005. (17) Singer, P. C.; Schneider, M.; Edwards-Brandt, J.; Budd, G. C. MIEX for Removal of DBP Precursors: Pilot Plant Findings. J. Am. Water Works Assoc. 2007, 99, 128. (18) Singer, P. C.; Bilyk, K. Enhanced Coagulation Using a Magnetic Ion Exchange Resin. Water Res. 2002, 36, 4009. (19) Boyer, T.; Singer, P. Bench-Scale Testing of a Magnetic Ion Exchange Resin for Removal of Disinfection By-Product Precursors. Water Res. 2005, 39, 1265. (20) Boyer, T. H.; Singer, P. C. A Pilot-Scale Evaluation of Magnetic Ion Exchange Treatment for Removal of Natural Organic Material and Inorganic Anions. Water Res. 2006, 40, 2865. (21) Hamm, E.; Bourke, M. Application of Magnetized Anion Exchange Resin for Removal of DOC at Coldiron Watkins Memorial Water Treatment Plant in Danville, KY. Presented at the AWWA Water Quality Technology Conference, Nashville, TN, Nov 11−14, 2001. (22) Shuang, C.; Pan, F.; Zhou, Q.; Li, A.; Li, P.; Yang, W. Magnetic Polyacrylic Anion Exchange Resin: Preparation, Characterization and Adsorption Behavior of Humic Acid. Ind. Eng. Chem. Res. 2012, 51, 4380. (23) Fearing, D. A.; Banks, J.; Guyetand, S.; Monfort Eroles, C.; Jefferson, B.; Wilson, D.; Hillis, P.; Campbell, A. T.; Parsons, S. A. Combination of Ferric and MIEX® for the Treatment of Humic Rich Waters. Water Res. 2004, 38, 2551. (24) Wert, E. C.; Edwards-Brandt, J. C.; Singer, P.; Budd, G. C. Evaluating Magnetic Ion Exchange Resin (MIEX)® Pre-Treatment to Increase Ozone Disinfection and Reduce Bromate Formation. Ozone Sci. Eng. 2005, 27, 371. (25) Gan, X.; Karanfil, T.; Kaplan-Bekaroglu, S. S.; Shan, J. The Control of N-DBP and C-DBP Precursors with MIEX®. Water Res. 2013, 47, 1344. (26) Bourke, M. Use of a Continuous Ion Exchange Process (MIEX®) to Remove TOC and Sulfides from Florida Water. Presented at the Florida Water Resources Conference, Jacksonville, FL, April 2001. (27) Rokicki, C. A.; Boyer, T. H. Bicarbonate-Form Anion Exchange: Affinity, Regeneration, and Stoichiometry. Water Res. 2011, 45, 1329.

the anion-exchange process in both low- and high-sulfate waters. Multiple-loading tests with MIEX resin provided 52% and 31% DOC removals in an average of 1500 BVs in low- and high-sulfate waters, respectively. On the other hand, much lower effluent DOC removals were obtained in low- (75%) and high- (46%) sulfate waters in continuous-flow tests of DOWEX 11. Whereas 81% of the sulfate was removed in low-sulfate water, almost no sulfate removal was obtained in high-sulfate water by MIEX resin. Increasing the sulfate concentration led to a reduction in DOC removal, and on average, 20% DOC removal was observed at the highest sulfate concentration of 600 mg/L. Whereas the sulfate removal was stable around 90%, it was reduced to 10−30% at elevated sulfate concentrations. Good correlations were obtained between the DOC removal and influent sulfate concentration (R2 = 0.96). In low-SUVA water sources, the removal of UV-absorbing organics by MIEX resin decreased as the influent sulfate concentration increased. Approximately 150 mg/L sulfate was taken up by the MIEX resin, and no sulfate benefit could be gained at sulfate concentrations of over 150 mg/L because of the developing equilibrium conditions between the resin and sulfate anion.

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ASSOCIATED CONTENT

S Supporting Information *

Analytical methods and equipment for the analysis of water quality parameters, kinetic tests of MIEX resin, UV254 changes in multiple-loading tests of MIEX resin and in continuous-flow tests of DOWEX 11 resin. This material is available free of charge via the Internet at http://pubs.acs.org.

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AUTHOR INFORMATION

Corresponding Author

*Tel.: +90 352 2076666 (ext. 32828). Fax: +90 352 437 5784. E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We express appreciation to Orica Watercare Co. for providing MIEX resin. We also express appreciation to Prof. Dr. Ulku Yetis for providing the opportunity to perform DOC analysis. This work was supported by Erciyes University, Scientific Research Foundation (Project BAP-10-3001).

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REFERENCES

(1) Krasner, S. W.; McGuire, M.; Jacangelo, J. G.; Patania, N. L.; Reagen, K. M.; Aieta, E. M. The Occurrence of Disinfection ByProducts in US Drinking Water. J. Am. Water Works Assoc. 1989, 81, 41. (2) Krasner, S. W.; Weinberg, H. S.; Richardson, S. D.; Pastor, S. J.; Chinn, R.; Sclimenti, M. J.; Onstad, G. D.; Thruston, A. D., Jr. Occurrence of a New Generation of Disinfection Byproducts. Environ. Sci. Technol. 2006, 40, 7175. (3) Krasner, S. W.; Amy, G. Jar-Test Evaluations of Enhanced Coagulation. J. Am. Water Works Assoc. 1995, 87, 93. (4) White, M. C.; Thompson, J. D.; Harrington, G. W.; Singer, P. C. Evaluating Criteria for Enhanced Coagulation Compliance. J. Am. Water Works Assoc. 1997, 89, 64. (5) McCreary, J. J.; Snoeyink, V. L. Characterization and Activated Carbon Adsorption of Several Humic Substances. Water Res. 1980, 14, 151. 14268

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4th IWA Specialty Conference on Natural Organic Matter: From Source to Tap and Beyond, Costa Mesa, CA, Jul 27−29, 2011.

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dx.doi.org/10.1021/ie401814v | Ind. Eng. Chem. Res. 2013, 52, 14261−14269