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Removal of Pharmaceutical and Personal Care Products from Reverse Osmosis Retentate Using Advanced Oxidation Processes Sihem Ben Abdelmelek,†,‡ John Greaves,§ Kenneth P. Ishida,|| William J. Cooper,† and Weihua Song^,†,* †
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Urban Water Research Center, Department of Civil and Environmental Engineering, University of California, Irvine, California 92697-2175, United States ‡ Department of Chemistry, Faculte des Sciences de Bizerte University of Carthage, Tunisia § Department of Chemistry, University of California, Irvine, California 92697-2025, United States Orange County Water District, Fountain Valley, California 92708, United States ^ Department of Environmental Science and Engineering, Fudan University, Shanghai 200433, P. R. China
bS Supporting Information ABSTRACT: The application of reverse osmosis (RO) in water intended for reuse is promising for assuring high water quality. However, one significant disadvantage is the need to dispose of the RO retentate (or reject water). Studies focusing on Pharmaceutical and Personal Care Products (PPCPs) have raised questions concerning their concentrations in the RO retentate. Advanced oxidation processes (AOPs) are alternatives for destroying these compounds in retentate that contains high concentration of effluent organic matter (EfOM) and other inorganic constituents. Twenty-seven PPCPs were screened in a RO retentate using solid phase extraction (SPE) and UPLC-MS/MS, and detailed degradation studies for 14 of the compounds were obtained. Based on the absolute hydroxyl radical (HO•) reaction rate constants for individual pharmaceutical compounds, and that of the RO retentate (EfOM and inorganic constituents), it was possible to model their destruction. Using excitation-emission matrix (EEM) fluorescence spectroscopy, the HO• oxidation of the EfOM could be observed through decreases in the retentate fluorescence. The decrease in the peak normally associated with proteins correlated well with the removal of the pharmaceutical compounds. These results suggest that fluorescence may be a suitable parameter for monitoring the degradation of PPCPs by AOPs in RO retentates.
’ INTRODUCTION Reverse osmosis (RO) is an attractive method for the reclamation of municipal wastewater because it removes a wide range of organic pollutants, bacteria and viruses, dissolved organic matter, and inorganic salts.1-5 However, a concentrate (retentate or reject water) is produced and usually this represents as much as 20 to 30% of the influent. As a result of the RO process the retentate can contain high concentrations of contaminants, and further treatment may be required before its disposal into the environment. Various technologies for the treatment of RO retentate have been investigated, including coagulation/flocculation,6 activated carbon adsorption,7 ozone-biological activated carbon,8 and river bank filtration.9 The effectiveness of these processes is influenced by the amount and type of effluent organic matter (EfOM) and inorganic constituents, both of which are factors that influence treatment costs. Advanced oxidation processes (AOPs) are alternatives for the destruction of micropollutants in the RO retentate. Limited r 2011 American Chemical Society
studies have been reported for this application.6,10 AOPs involve the formation of the hydroxyl radical (HO•), as an oxidizing species, that is able to degrade a range of organic compounds in water.11-14 However, one concern of AOPs is the competition for the HO• between the EfOM, the inorganic constituents, and the micropollutants of interest. This study focused on the feasibility of degrading pharmaceutical and personal care products (PPCPs) in RO retentate using AOPs. PPCPs are classified as emerging pollutants of concern due to their widespread use, incomplete removal during wastewater treatment, and the fact that they are not regulated.15 The site studied, the Advanced Water Purification Facility (AWPF) at the Orange County Water District (Fountain Valley, California), treats wastewater effluent from the Orange County Sanitation Received: December 21, 2010 Accepted: February 14, 2011 Revised: February 10, 2011 Published: March 08, 2011 3665
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Environmental Science & Technology District (OCSD), which consists of 20% trickling filter and 80% activated sludge effluents. The AWPF treats this wastewater using microfiltration, RO and UV/H2O2, to achieve indirect potable water quality for reuse both as a seawater intrusion barrier and for infiltration to supplement groundwater supplies. The RO retentate from the AWPF is returned to OCSD. Although there are several studies on the degradation of PPCPs from RO retentate by ozonation,8,10,16 there are no detailed kinetic and/or modeling studies of HO• mediated degradation of PPCPs in RO retentate. Twenty-seven PPCPs were screened for, in the RO retentate, using solid phase extraction (SPE) and UPLC-MS/MS. Eighteen pharmaceuticals were identified as occurring in the retentate at μg L-1 concentrations. To provide insight into the potential utility of AOP treatment, N2O saturated samples of RO retentate were subjected to γ-irradiation at various absorbed doses. The N2O was used to isolate HO• as the only oxidant. Absolute reaction rate constants were used to estimate the initial degradation rates of PPCPs in the RO retentate. Additionally, there is a need to develop surrogates and indicators to assess the removal efficiency of PPCPs during AOP operations, since it is both highly time and cost intensive to determine extremely low levels of individual PPCPs in wastewater effluents.17 Prior research has shown that the changes in the UV absorbance, A254 (ΔA254) and/or the color of wastewater effluents are correlated with the degree of removal of many endocrine disrupting compounds (EDCs)/PPCPs during O3 oxidation or O3/H2 O2 treatment.18-20 However, there are no studies that have evaluated excitation emission matrix (EEM) fluorescence of RO retentate and the potential changes in the fluorescence spectra, during advanced oxidation treatment, as PPCPs are degraded. The current study is a first step to assess the HO• oxidation of EfOM and the removal of a complex mixture of PPCPs in RO retentate waters and evaluation of EEM fluorescence spectra as a monitoring tool.
’ EXPERIMENTAL SECTION Chemicals and Standards. All chemical standards were >99% pure and were purchased from Sigma-Aldrich (St. Louis, MO, USA). The isotopically labeled compounds used as internal standards, Ibuprofen-D3 (>99%) and Carbamazepine-D10 (>99%), were from CDN Isotopes (Quebec, Canada) and were donated by the OCSD. The cartridges used for solid phase extraction (SPE) were Oasis HLB (500 mg, 60 μm, 12 mL) from Waters Corporation (Milford, MA, USA). Individual stock solutions of the pharmaceuticals were prepared in methanol at 1 mg mL-1. A mixture of all the pharmaceuticals was then prepared in methanol with each compound present at 30 mg mL-1. Calibration standards were diluted from this mixed standard with methanol/water (25/75). Individual internal standard stock solutions were prepared in methanol at 0.1 mg mL-1. A mixture of internal standards was then prepared in methanol and further diluted in methanol/water (25/75). All standards were stored at 4 C. Sample Pretreatment and Solid Phase Extraction. Samples were collected in amber glass bottles, filtered through 0.2 μm filters (Fisher, Pittsburgh, PA), and stored at 4 C. The typical water quality was shown in Table 1S, Supporting Information. The protocol for the SPE extraction was adapted from Gros et al.21,22 Retentate samples, 100 mL, were combined with
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100 mL of Milli-Q water, 2 mL of Na2EDTA (5% solution), and 1 mL of a 500 ng mL-1 solution containing both the internal standards and extracted using 500 mg Oasis HLB cartridges. The cartridges were preconditioned by washing with methanol (6 mL) followed by Milli-Q water (6 mL). The samples were loaded onto the column at a flow rate of approximately 5 mL min-1. The cartridges were then rinsed with 5 mL of Milli-Q water and dried under vacuum for 15 min. Analytes were eluted with 2 4 mL of methanol. The combined extracts were evaporated to dryness under a gentle nitrogen stream followed by reconstitution with 1 mL of methanol/water (25/75, v/v). The RO retentate samples were preserved with phosphoric acid prior to analysis for dissolve organic carbon (DOC) using a GE/Sievers 5310C TOC analyzer. The concentration of DOC was 22.1 mg L-1. LC-MS/MS Analysis. Chromatographic separation utilized a Waters Acquity UPLC system equipped with an Acquity BEH C18 column (2.1 50 mm, 1.7 μm particle size), using mobile phases A (water supplemented with 2% acetonitrile and 0.2% acetic acid) and B (acetonitrile acidified with 0.2% acetic acid). The gradient started at 90% A with a linear increase to 90% B in 1 min where it was held for 1 min followed by a return to 90% A at 2.05 min with a hold of 0.95 min at 90% A, giving a total cycle time of 3 min. The flow rate was 0.3 mL min-1. The column oven temperature was set at 50 C. An injection volume of 10 μL was used for all analyses. The UPLC was coupled to a Waters Quattro Premier XE triple quadrupole mass spectrometer (MS), and the parameters for the analyses were: desolvation and ESI source block temperatures, 400 and 125 C, respectively; capillary voltage, 3.3 kV; argon collision gas, 7 10-3 mbar. For quantitative analyses, the MS was operated in multiplereaction monitoring (MRM) mode. Transitions were selected, and cone voltages and collision energies were optimized for each analyte using MassLynx 4.1 QuanOptimize software. For each compound, the most abundant fragment ion (Table 1) was used for quantification with a secondary transition being used to confirm identifications. Pulse Radiation and γ Radiation. Electron pulse radiation was employed to determine absolute HO• rate constants for the RO retentate and individual PPCPs. These experiments were conducted at the Notre Dame Radiation Laboratory with an 8-MeV Titan Beta model TBS-8/16-1S linear accelerator.11-13 Dosimetry for the system was based on the transient absorbance produced in N2O-saturated 1.00 10-2 M, KSCN solutions at λ = 472 nm, (Gε = 5.2 10-4 m2 J-1) with average doses of 35 Gy per 2-3 ns pulse. The experimental data were determined by averaging 15 replicate pulses, using a continuous flow method, for the solution being studied. The radiolysis of water forms reactive species, such as HO•, H•, e-aq, and is described in eq 1, where the numbers in parentheses are μmol J-1 and represent efficiencies of formation23
Reactions with just the hydroxyl radical were achieved by using nitrous oxide (N2O) presaturated solutions, that quantitatively converted solvated electrons (e-aq) and hydrogen atoms (H•) to the HO• radical. A Shepherd 109-86 60Co source was used for γ radiation of RO retentate saturated with N2O. The dose rate was 11.2 Gy min-1 (1.12 krad min-1) as measured by Fricke dosimetry. 3666
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Table 1. MS/MS Parameters for the Analysis of the Targeted Pharmaceutical Compounds and Their Concentrations in RO Retentate standard
IDL
R0
mode
MS transition
curve R2
(μg L-1)a
(μg L-1)b
gemfibrozil
-
249f121
0.9956
0.02
6.979
naproxen
-
229f170
0.9984
0.02
1.416
carbamazepine
þ
237f194
0.9931
0.01
0.134
ofloxacin erythromycin
þ þ
362f318 734f576
0.9920 0.9942
0.01 0.1
0.299 7.984
trimethoprim
þ
291f230
0.9975
0.4
1.124
venlafaxine
þ
278f260
0.9933
0.2
0.333
atenolol
þ
267f190
0.9979
0.2
2.634
metoprolol
þ
268f116
0.9924
0.1
0.470
caffeine
þ
195f138
0.9937
0.1
0.708
nalidixic acid
þ
233f187
0.9976
0.01
0.189
iohexol deet
þ þ
822f804 192f119
0.9950 0.9344
0.1 0.01
2.400 0.766
sulfamethoxazole
þ
254f156
0.9991
0.4
0.437
atorvastatin
þ
559f440
0.9852
0.1
NDc
lovastatin
þ
405f285
0.9989
0.1
NDc
enrofloxacin
þ
360f316
0.9478
0.01
NDc
sulfamethazine
þ
279f186
0.9963
0.1
NDc
sulfamethizole
þ
271f156
0.9996
0.5
NDc
sulfamerazine cimitidine
þ þ
265f156 253f159
0.9999 0.9923
0.1 0.2
NDc NDc
famotidine
þ
338f189
0.9966
0.2
2.1
ranitidine
þ
315f176
0.9829
2
NDc
5,5 diphenyl-
þ
253f182
0.9994
0.1
0.145
iopamidol
þ
778f559
0.9947
0.2
2.626
iomeprol
þ
778f687
0.9988
0.1
0.386
iopromide
þ
792f573
0.9954
2
compounds
hydantoin
a
b
NDc c
IDL: instrumental detection limit. R0: initial concentration. ND: not detected.
Excitation Emission Matrix Florescence. EEM spectra of the RO retentate were recorded using a FluoroMax-4 (Horiba-Jobin Yvon). The fluorometer was set up as follows: the excitation wavelength was incrementally increased from 240 to 500 nm in 5-nm intervals, with emission monitoring from 280 to 600 nm at 5-nm intervals for each excitation wavelength. All RO retentate samples were diluted 10 times using Optima LC/MS water. The intensity of all EEM spectra was normalized, on a daily basis, by dividing by the area of the Raman water line obtained using 350 nm excitation and 397 nm emission wavelengths. The FL Tool Box software was used to correct the spectra for Raman and Raleigh scattering and to calculate EEM peak integrals.24 Quinine sulfate standards were used to calibrate the EEM spectra, and fluorescence intensities were expressed in units of quinine sulfate equivalents (QSE).25
’ RESULTS AND DISCUSSIONS Screening of PPCPs in the RO Retentate. Twenty-seven PPCPs (Table 1) were screened for, in this study, as these have been frequently detected in treated wastewater effluent.26 Nine compounds (Atorvastatin, Lovastatin, Enrofloxacin, Sulfamethazine, Sulfamethizole, Sulfamerazine, Cimitidine, Ranitidine, and
Iopromide) were not found, while 18 compounds were identified in the RO retentates with concentrations that ranged from 0.1 to 7.9 μg L-1, as shown in Table 2. (Note: Often concentrations of compounds are reported in the literature in units of weight per volume, e.g. μg L-1; however, when developing models it is necessary to use moles per volume, which is done later in this paper.) Those detected at the highest concentrations were Gemfibrozil, Naproxen, Erythromycin, and Atenolol, in agreement with other studies suggesting that conventional biological treatment is relatively inefficient in removing these compounds.27,28 Kinetic Studies of HO• Oxidation of PPCPs. To explore the kinetic details for the removal of PPCPs by AOPs, steady-state γirradiation of RO retentate was employed under N2O saturated conditions. The results showed decreasing PPCP concentrations with increasing irradiation doses. Of the 18 PPCPs found, the degradation of 14 were measured, while the four remaining (Famotidine, 5, 5-Diphenylhydantoin, Iopamidol, and Iomeprol) were not quantified due to their low initial concentration. The degradation curves were consistent with previous reported irradiation studies for other contaminants in wastewater effluent.29,30 The initial degradation rate for the individual PPCPs is the tangent to the curve at time zero, as illustrated by the hatched line in Figure 1a for Atenolol. The experimentally determined degradation rates for the 14 PPCPs are summarized in Table. 2. Reaction Rate Constant for HO• and RO Retentate. To model the initial degradation rates of PPCPs in the RO retentate, it was first necessary to determine the bimolecular reaction rate constant of HO• and RO retentate. These studies were performed on a sample of RO retentate which included both the organic and inorganic constituents. The overall reaction rate constant was determined by competition kinetics with SCN(eq 2 and 3) based on monitoring the (SCN)2•- absorption at 472 nm (Note: EfOM is a simplification and includes organic and inorganic constituents (Table S1) and the PPCPs. By evaluating the overall reaction rate constant, using competition kinetics, the ‘apparent rate constant’ that was obtained includes all of the constituents that react with HO•, as opposed to observing the growth of the transient absorption spectra of just the EfOM.) k2
HO• þ EfOM sf H2 O þ Intermediate k3
HO• þ SCN- ð þ SCN- Þ sf OH- þ ðSCNÞ2 •The following equation was solved to estimate the k2 ½ðSCNÞ•-2 0 k2 ½EfOM •- ¼ 1 þ k3 ½SCN- ½ðSCNÞ2
ð2Þ ð3Þ
ð4Þ
where [(SCN)2•-]0 is the absorbance of this transient at 472 nm when only SCN- is present, and [(SCN)2•-] is the reduced yield of this transient when the substrate (RO retentate) was present. Therefore, a plot of [(SCN)2•-]0/[(SCN)2•-] against the [EfOM]/[SCN-] should give a straight line of slope k2/k3. On the basis of the established rate constant for hydroxyl radical reaction with SCN-, k3 = 1.05 1010 M-1 s-1, the rate constant (k2) for EfOM can be calculated. The rate constant of EfOM is reported as the molar concentration of DOC, assuming 12 gC per mole C. Kinetic data obtained at 472 nm are shown in Figure 2a, and, as expected, a decrease in the maximum (SCN)2•- absorption 3667
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Table 2. Selected Pharmaceutical Compounds, Their Structures, Bimolecular HO• Reaction Rate Constants, and Experimental and Calculated Degradation Ratesa
a
The * denotes reaction rate constants, refer to Supporting Information.
intensity was observed when increasing amounts of RO retentate were added. The transformed plot shown in Figure 2b gives a weighted linear fit kOH,EfOM = (5.18 ( 0.13) 108 MC-1 s-1. This rate constant was similar to the average value of (8.6 ( 3.5)
108 MC-1 s-1, recently reported for nonisolated EfOM in wastewater.31 Modeling Data for HO• Oxidation of PPCPs in the RO Retentate. Although several studies indicated the HO• radical 3668
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Figure 1. (a) Measured loss of Atenolol in N2O saturated RO retentate using 60Co γ-irradiation. The curve corresponds to fitted loss (9), while the dashed straight line (- - -) is the experimentally determined initial degradation rate, 0.533 nM min-1. (b) Summarizes the relationship between the experimentally determined degradation rate and the calculated rate based on eq 5. (Note: The initial data were plotted in a nonlog format from which the statistics were obtained. For clarity in presentation they were transformed to log-log format to better visualize the data points and allow for insertion of the pharmaceutical names.) 29,32
reaction efficiency with PPCPs may vary, we assumed that the efficiency is 100% to simplify the model. The calculated degradation slopes or reaction (loss) rate of a PPCP can be expressed as the fraction of HO• that reacts with the PPCPs, as in eq 5 Calculated slopeðnMmin-1 Þ ¼ G dose rate
Initial Conc:½PPCPs k OH, PPCPs Initial Conc:½EfOM k OH, EfOM
ð5Þ
The absorption coefficient was calculated using a G-value of 0.59 μmol J-1 for the hydroxyl radical in N2O saturated solutions, based upon the intraspur scavenging model calculations.33 The HO• radical reaction rate constants, for the individual PPCPs, kOH, PPCPs, were obtained from the literature or measured by pulse radiation (the experimental details are in Supporting Information, Figure 1S to 5S). The calculated degradation rates obtained from eq 5 (Figure 1b) for the 14 PPCPs, based on the absolute HO• reaction rate constants, showed excellent (linear) correlation with experimentally determined degradation slope from γ irradiation (R2 = 0.98, n = 14). This result suggested that the combination of HO•
Figure 2. (a) Kinetics of (SCN)2•- formation at 472 nm for N2O saturated 1.00 10-4 M KSCN solution containing 0 ()), 0.772 (r),1.107 (Δ), 1.378 (O), and 1.842 (0) mMC RO retentate. (b) Competition kinetic plot for hydroxyl radical reaction with RO retentate using SCN- as a standard. Solid line is a weighted linear fit with a slope of 0.0457 ( 0.0011. This gives a second-order rate constant for the degradation rate of RO retentate, kOH,EfOM = (5.18 ( 0.13) 108 MC-1 s-1.
reaction rate constants of individual PPCPs and the bulk EfOM may be an effective tool to evaluate the likelihood of effective removal of PPCPs by AOPs. In other studies, the correlation of HO• rate constants with nonisolated EfOM was evaluated, and an empirical equation that included terms relating to UV absorption, fluorescence index of EfOM, and polarity was obtained.31 According to both results, it is possible to estimate the effectiveness of AOPs for removing specific PPCPs based on absolute HO• reaction rate constants and bulk EfOM physical-chemical properties. Correlation between EEM Spectra and PPCPs Oxidation. In addition to predicting the degradation rate of PPCPs using absolute reaction rate constants, the progressive changes observed in EEM spectra of RO retentate during HO• radical oxidation were investigated. Three peak integrals were identified from the original RO retentate as illustrated in Figure 3. Based upon the classification of EEM fluorescent peaks as described in previous studies,25,34-37 these peaks were assigned as follows: UV humic-like peak (excitation: 240-265 nm, emission: 400500 nm), visible humic-like peak (excitation: 320-360 nm, emission: 420-460 nm), and protein-like peak (excitation: 260290 nm, emission: 300-350 nm). Steady-state irradiation of RO retentate, under N2O saturated conditions, decreased the intensity of these three peaks as the dose increased (Figure 6S, Supporting Information). The UV humic-like peak degradation was similar to that of the visible 3669
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Figure 3. Fluorescence excitation-emission matrix spectra of RO retentates. Three major peaks were identified as UV humic-like, visible humic-like, and protein-like.
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comparison, there was no significant change of the UV spectrum in RO retentate when HO• was the sole oxidant under our experimental conditions (Figure 8S, Supporting Information). These results suggest that ozone was more selective and reacted with specific chromophores in the EfOM which resulted in the loss of UV absorbance. Hydroxyl radical reacts nonselectively with aromatic groups resulting in the loss of fluorescence; however, no loss of UV-vis absorbance at the low HO• exposure used in this study was observed (Figure S8). Implications. The results presented above indicate that AOPs can effectively remove PPCPs from RO retentates in the presence of both organic and inorganic constituents. This is the first attempt to evaluate the kinetics of HO• oxidation of PPCPs and to model their degradation in RO retentate. The bimolecular reaction rate constants of individual PPCP and RO retentate (EfOM) were employed to predict the removal rate of PPCPs, and the calculated results are in accordance with the experimental results. Additionally, the removal of PPCPs is well correlated with the reduction of protein-like fluorescence of RO retentate, suggesting that monitoring the changes of this florescence peak may provide a rapid and inexpensive method for the quantitative estimation of PPCPs degradation under treatment plant conditions.
’ ASSOCIATED CONTENT
bS
Supporting Information. Table S1 and Figures 1S-8S. This material is available free of charge via the Internet at http:// pubs.acs.org
’ AUTHOR INFORMATION Corresponding Author
*Phone: (86)-21-6564-2040. E-mail:
[email protected],
[email protected]. Figure 4. Relative intensity of the fluorescence peaks as a function of HO• oxidation. (9 UV humic-like peak: λex = 245 nm, λem = 459 nm, ( visible humic-like peak: λex = 345 nm, λem = 445 nm, 2 protein-like peak: λex = 276 nm, λem = 329 nm).
humic-like peak; however, they were both significantly different from the protein-like peak, as shown in Figure 4. The loss of fluorescence of the humic-like peaks did not exhibit the simple first-order decay that was observed for the protein-like peak. This suggested that some components of humic matrixes were more resistant to HO• oxidation than was the protein-like peak. The association of the changes in the EEM spectra with the removal of individual PPCPs was evaluated. The results showed that the removal of PPCPs approached 80 to 100%, while there was a 40 to 50% reduction of UV and visible humic-like peaks (as illustrated in Figure 7S, Supporting Information). At the same time, the protein-like peak showed good correlation with individual PPCP removal up to 80%. This result suggests that monitoring the protein-like peak may be a suitable indicator for evaluating the HO• radical loss of PPCPs in RO retentates. In previous work, several research groups have reported UV254 absorbance and color changes as methods for assessing the removal of PPCPs from wastewater effluent being treated by oxidation with O3 or O3/ H2O2.19,20 The relative decrease of absorbance (ΔA/A0) ranged from 80% for λ > 320 nm. The removal of PPCPs correlated very well with ΔA/A0 values.20 In
’ ACKNOWLEDGMENT Pulse radiation experiments were performed at the Radiation Laboratory, University of Notre Dame, supported by the Office of Basic Energy Sciences, U.S. Department of Energy. This research was funded in part by the NSF (CBET-1034555) and WateReuse Foundation (WRF-08-11). This is contribution 60 from the Urban Water Research Center, University of California, Irvine. ’ REFERENCES (1) Wintgens, T.; Melin, T.; Schafer, A.; Khan, S.; Muston, M.; Bixio, D.; Thoeye, C. The role of membrane processes in municipal wastewater reclamation and reuse. Desalination 2006, 187, 271–282. (2) Comerton, A. M.; Andrews, R. C.; Bagley, D. M. Evaluation of an MBR-RO system to produce high quality reuse water: microbial control, DBP formation and removal. Water Res. 2005, 39 (16), 3982–3990. (3) Snyder, S. A.; Adham, S.; Redding, A. M.; Cannon, F. S.; DeCarolis, J.; Oppenheimer, J.; Wert, E. C.; Yoon, Y. Role of membranes and activated carbon in the removal of endocrine disruptors and pharmaceuticals. Desalination 2007, 202, 156–181. (4) Kimura, K.; Iwase, T.; Kita, S.; Watanabe, Y. Influence of residual organic macromolecules produced in biological wastewater treatment processes on removal of pharmaceuticals by NF/RO membranes. Water Res. 2009, 43 (15), 3751–3758. 3670
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